Light scattering studies of several cationic detergents
by Edwin H Eylar
A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree
of Master of Science in Chemistry
Montana State University
© Copyright by Edwin H Eylar (1955)
Abstract:
Aqueous solutions of various dodecylalkyl-, dodecyldialkyl- , dodecyltrialkylammonium chlorides and
dodecyltrimethyl-ammonlum halides were examined by light scattering methods in an attempt to gain
further insight into the phenomenon of micelle formation. Molecular weights of micelles formed by
these surface active agents and their critical concentrations were measured. Micelle size was found to
be influenced both by the nature of the gegen ion and the makeup of the substituent groups on the
nitrogen atom. Dodecylmethylammonium chloride micelles (the largest) were found to have a
molecular weight of approximately 74,600 while dodecyltrimethylammonium chloride micelles were
found to have molecular weights in the neighborhood of 9,300. LIGHT SCATTERING STUUEES
OP
SEVEBAL CATIONIC DETERGENTS
by
BUSIN H. ESCLAR
A THESIS
S u b m itted to th e G raduate F a c u lty
in
p a r t i a l f u l f i l l m e n t o f th e re q u ire m e n ts
f o r th e d e g re e o f
M aster o f S c ie n c e
i n C hem istry
Montana S ta te C o lleg e
Approved*
Head, Major D epartm ent
I
Bozeman, Montana
Ju n e , 1956
2
TABLE OF CONTam
I . A b s tr a c t
.
.
.
.
.
Page
3
.
.
4
,
•
12
•
•
12
....................................
14
3 . S e r ie s I I I
....................................
15
4 . S e r ie s IV
.
.
17
I I . I n tr o d u c tio n
.
.
.
I I I . P re p a r a tio n of D e te rg e n ts
1 . S e r ie s I
•
2 . S e r ie s I
I
•
.
•
.
.
5 . G eneral Remarks •
.
•
•
18
6. R eagents
•
.
.
20
IV . A pparatus
•
.
.
•
.
.
.
V. E xperim ental Methods
•
.
«
22
•
26
.
.
.
.
.
.
35
V II. D isc u ssio n .
.
.
.
.
.
42
V I. R e su lts
•
•
•
•
•
50
IX , Acknowledgements
•
•
•
•
52
X. L i t e r a t u r e C ite d
•
•
•
•
53
V I I I . B rie f Summary
i ' *7 T
3
I . ABSTRACT
Aqueous s o lu tio n s o f v a rio u s d o d e c y la lk y l- , d o d e o y ld ia lk y l - , dodeoyltrialkylanm ionium c h lo r id e s and d o d e c y ltrim e th y lammonium h a l id e s w ere examined by l i g h t s c a t t e r i n g methods in
an a tte m p t to g a in f u r t h e r i n s i g h t i n t o th e phenomenon o f mi­
c e l l e fo rm a tio n . M o lecu lar w e ig h ts o f m ic e lle s form ed by th e s e
s u r f a c e a c t i v e a g e n ts and t h e i r c r i t i c a l c o n c e n tr a tio n s were
m easured. M ic e lle s i z e was found to be in f lu e n c e d b o th by th e
n a t u r e o f th e gegen io n and th e makeup of th e s u b s t i t u e n t
groups on th e n itr o g e n atom . Dodeoylmethylamraonlm c h lo r id e
m ic e lle s ( th e l a r g e s t ) were found to have a m o le c u la r w eig h t of
a p p ro x im a te ly 74,600 w h ile dodecyltriraethylam m oniim c h lo r id e
m ic e lle s were fo u n d t o have m o le c u la r w eig h ts i n th e n e ig h b o r­
hood o f 9 ,3 0 0 .
4
II.
INTRODUCTION
McBaln (20) I n 1915 co n clu d ed t h a t c e r t a i n abnorm al p ro p ­
e r t i e s e x h ib ite d by so ap s I n s o lu tio n c o u ld b e s t b e e x p la in e d
by assum ing t h a t th e lo n g -c h a in Io n s o f th e soap* came to g e th ­
e r to form la r g e c o l l o i d a l a g g r e g a tio n s , w hich w ere l a t e r
term ed m ic e l le s .
S o lu tio n s o f s u r f a c e a c t i v e a g e n ts have been
s tu d ie d q u ite e x te n s iv e ly by o sm otic p r e s s u r e , u l t r a c e n t r i f u g e ,
d if f u s io n , X -ray , c o n d u c tiv ity , and l i g h t s c a t t e r i n g methods
i n o rd e r to d eterm in e s t r u c t u r e , sh ap e, w e ig h t, and o th e r
c h a r a c t e r i s t i c s o f t h e i r m ic e l le s .
S in ce l i g h t s c a t t e r i n g was
used i n t h i s i n v e s t i g a t i o n , a b r i e f rev iew o f th e th e o ry f o l ­
lows ( 2 , 4 , 8 , 9 ) .
The t u r b i d i t y T o f a s c a t t e r i n g medium i s d e fin e d by
T = -A -J L .
I
dL
I n t e g r a t i o n g iv e s
i =
I 0 i s th e i n t e n s i t y o f th e in c id e n t l i g h t and I i s th e i n t e n ­
s i t y o f th e l i g h t a f t e r p a s s in g th ro u g h L cm. o f th e medium.
A ccording to e le c tro m a g n e tic th e o ry , th e i n t e n s i t y of
l i g h t s c a t t e r e d from a s m a ll, i s o l a t e d , i s o t r o p i c , d i e l e c t r i c
2tMcBain s tu d ie d compounds l i k e p o ta ssiu m s t e a r a t e , w hich
i s p ro p e r ly d e s ig n a te d a " s o a p ." However, th e compounds con­
s id e r e d i n t h i s s tu d y sh o u ld n o t, a c c o rd in g to th e cowaonly
a c c e p te d n o m e n c la tu re , be term ed so ap s b u t s h a l l be r e f e r r e d
to th ro u g h o u t t h i s t h e s i s a s " d e te r g e n ts * o r " s u r f a c t a n t s .*
5
p a r t i c l e —when e x c ite d by m p o la r lz e d l i g h t o f i n t e n s i t y I 0Is
, 8
tt* ( 1
+ cos
6
) CX
r2 A 4
<X
i s th e p o l a r i z a b i l i t y o f th e s c a t t e r i n g c e n t e r .
A . i s th e wave le n g th of th e i n c id e n t and s c a t t e r e d l i g h t " in
v ac u o ."
r
i s th e d is ta n c e from th e s c a t t e r i n g p a r t i c l e to th e p o in t
o f o b s e r v a tio n .
©
i s th e a n g le betw een th e in c id e n t beam and th e d i r e c t i o n i n
w hich th e s c a t t e r i n g i s o b se rv e d .
An e x p re s s io n f o r th e t u r b i d i t y o f an i d e a l gas c o n s is tin g
o f n in d e p en d en t m o le cu les ( s c a t t e r i n g c e n te r s ) p e r cu b ic ce n ­
tim e te r can b e c a l c u l a t e d .
th e shape o f a d is k .
C o n sid er a sm all volume of gas w ith
The f a c e s o f th e d is k a r e p e rp e n d ic u la r
to th e d i r e c t i o n o f p ro p a g a tio n o f th e in c id e n t l i g h t .
The
d is k volume i s AdL w here A i s f a c e a r e a and dL i s d is k th ic k ­
n ess.
The i n t e n s i t y I e o f th e s c a t t e r e d l i g h t a t a d is ta n c e r
from th e d is k ( r » A&), and a t an a n g le 0 w ith th e in c id e n t
beam i s
,
Ie -
8
T t4 U
4- c o s 2 6
) CA2
----- ---------------- I 0HAdL
Vti A 4
Now c o n s id e r a sp h e re o f r a d iu s r w ith th e d is k of gas a t
i t s c e n te r ( r » A&) and a sm a ll zone o f t h i s s p h e re whose de­
f i n i n g p la n e s a r e _L to th e a x is o f p ro p a g a tio n o f th e i n o i -
6
dent lig h t .
IBie a n g le betw een any r a d iu s v e c to r to th e zone
and th e a x is o f p ro p a g a tio n o f th e in c id e n t l i g h t I s 0 .
w id th o f th e zone i s rd©
2 IT r ^ s i n 0 d©
•
The
and i t s a r e a ap p ro x im a tely
Ih e energy r a d i a t e d each second th ro u g h th e
zone i n th e form o f s c a t t e r e d l i g h t i s
8 TT4 U -+- cos2 6
) < *2
dB = ------------- g - ' --------------- I eHAdLSTT r ^ s i n e d©
The t o t a l energy r a d i a t e d each second th ro u g h th e sp h e re
due to s c a t t e r i n g o f th e in c id e n t l i g h t by th e gas m o lecu les
w ith in th e d is k i s
S
2
T l n <X Al dL
E=
—
8 IT
/ 2 TT \ 4
—
(—
J
s in 0
( I 4- cos2 0
)d 0
2
n ° ( A I «dL
The d e c re a s e i n i n t e n s i t y , d l , o f th e p rim a ry beam, w ith
i n t e n s i t y = I 0, due to s c a t t e r i n g by th e gas m o le cu les i n th e
d is k i s - V a »
T
Hence
I
dl
E IS T
8 TT
/ 2 TTX
—
\—
J
A ccording to e le c tro m a g n e tic th e o ry th e p o l a r i z a b i l i t y of
an i d e a l gas i s r e l a t e d to th e r e f r a c t i v e in d e x , ji, by
2
^
) 8
4 TT2 n 2
7
so t h a t
T = t u r b i d i t y o f an I d e a l gas =
S2TT-S ( y - 1 ) 2
S A 4H
Thus f a r o n ly s c a t t e r i n g from a d i l u t e gas h as been con­
s id e r e d ,
However, th e a p p l ic a tio n t o s o lu tio n s I s e a s ily made
w ith th e a i d o f s im p lif y in g assu m p tio n s a lre a d y p ro p o sed , i , e . ,
t h a t th e m o le cu les a r e I s o t r o p i c ; t h a t th e y a r e sm a ll compared
to A ; t h a t s o lu t e m o le cu les a r e random ly d i s t r i b u t e d in s o lu ­
t i o n (hence s o lu t io n i s v ery d i l u t e ) ; and t h a t th e l i g h t s c a t ­
te r e d from th e s o lu te m o lecu les i s g iv en as th e d if f e r e n c e b e ­
tw een t o t a l s c a t t e r i n g and l i g h t s c a t t e r e d from s o lv e n t m ole­
c u le s ,
The p o l a r i z a b i l i t y , <X , i n t h i s c a se i s g iv en by*
—
2 IT b
or
/V f-z V
'Z i-Z1O]
= 2 TT ('< C /
and
M
N
2
f ^ - / iO
2 _ P-o2 1I
)
C
(A — ......
4 IT 2N2
*
T h e re fo re , f o r a s o lu t io n a t lew c o n c e n tr a tio n
»3 IT V
(^ 4
T = ----------------------:------- CM
8
w here
= r e f r a c t i v e In d ex o f s o lu t io n ,
J io = r e f r a c t i v e in d e x o f s o lv e n t,
C = c o n c e n tr a tio n o f s o lu t e i n g . / c o . ,
N = Avogadro’ s number,
M = m o le c u la r w e l^ a t o f s o lu t e p a r t i c l e .
An e x p re s s io n more a c c u r a te a t h ig h e r c o n c e n tr a tio n s was
d e riv e d by E in s te in .
He was a b le to r e l a t e o sm o tic p r e s s u r e
p and t u r b i d i t y Ti
=■
>■*=w
( * )
For m ost s o lu tio n s
• i s p r a c t i c a l l y c o n s ta n t a t lew conyC
U-U0
c e n t r a t i o n , and can be r e p la c e d by
— . A g e n e ra l e x p re s s io n
f o r th e osm otic p r e s s u r e i n term s o f c o n c e n tr a tio n i s a power
s e r i e s ex p an sio n i n term s o f C$
- P - = I + BC -h CC2 + DC3 +
RTC
H
..............
w here B i s c a l l e d th e i n t e r a c t i o n c o n s ta n t and i s a f u n c tio n ©f
th e s o lv e n t and s o lu t e p a i r , b u t i s In d ep en d en t o f th e m olecu­
l a r w eig h t o f th e s o l u t e .
in d ilu te s o lu tio n .
Hence
•"1
ac
and
Only th e B term need be c o n s id e re d
( --P- — — + 2BC
\ RT /
M
E = I 4-S-BC
I
H
9
w here
2
^
M t r jV 08
(
SN A4
Vihen HC/T I s p l o t t e d a g a in s t C, a s t r a i g h t l i n e i s u s u a lly
o b ta in e d where M, th e m o le c u la r w e ig h t. I s eq u al to th e r e c i p ­
r o c a l o f th e HC/T i n t e r c e p t .
For p a r t i c l e s e x h ib itin g a n ! s o t-
ropy a d e p o la r iz a tio n c o r r e c t io n m ust be made,
ft
Debye and o th ­
e r s have d ev elo p ed fo rm u la s from w hich shape o f p a r t i c l e s w ith
dim ensions g r e a t e r th a n l / 2 0
A can
be d eterm in ed by m easuring
th e a n g u la r dissym m etry of th e s c a t t e r e d l i g h t .
She p u rp o se of t h i s i n v e s t i g a t i o n was to d e te rm in e m olecu­
l a r w eig h ts o f m ic e lle s of s e v e r a l s e r i e s o f d e te r g e n ts i n th e
hope t h a t a c o r r e l a t i o n o f th e d a ta m ight r e v e a l in fo rm a tio n
c o n c e rn in g th e s t r u c t u r e o f th e c a t i o n i c m i c e l l e s ,
A su rv ey o f
th e l i t e r a t u r e shows t h a t much d isa g re e m e n t e x i s t s among in v e s ­
t i g a t o r s r e g a r d in g m ic e lle shape and s i z e .
H a rtle y su p p o rte d
th e view t h a t o n ly s p h e r ic a l m ic e lle s a r e l i k e l y ( 1 3 ),
MoBain
(19) h as c i t e d e v id e n c e f o r two m ic e lle s t r u c t u r e s , s p h e r ic a l
and la m e l la r .
He a ls o g iv e s ev id en ce t h a t some m ic e lle s con­
t a i n th i c k la y e r s of Im m obilized w a te r .
A rev ie w o f m ic e lle
l i t e r a t u r e may b e fo u n d i n a r e c e n t p ap er (1949) by Debye ( 5 ) .
L ig h t s c a t t e r i n g m ethods have proven v a lu a b le i n s tu d ie s
ft
I f a s c a t t e r i n g p a r t i c l e i s i s o t r o p i c th e l i g h t s c a t t e r e d
a t 90® i s l i n e a r l y p o la r iz e d . I f d e p o la r iz a tio n i s o b serv ed i t
means th a t th e p a r t i c l e s a r e n o t I s o t r o p i c . Cabannes and Debye
have in d ic a t e d th e a p p r o p r ia te c o r r e c t io n to be made.
10
In v o lv in g la r g e m o le c u le s .
I f th e s o lu tio n c o n ta in s p a r t i c l e s
o f d i f f e r e n t w e ig h ts , l i g h t s c a t t e r i n g g iv e s a w e ig h t-a v e ra g e
m o le c u la r w e ig h t.
I n th e p r e s e n t in v e s t i g a t i o n q u a te rn a ry am­
monium s a l t s w ere u se d .
were a p p a re n t.
Mo c o m p lic a tio n s b e c a u se o f h y d r o ly s is
I n a l l c a s e s th e i n t e n s i t y o f th e s c a tte r e d
l i g h t was m easu red .
T ran sm issio n d a ta have b een u sed by some
In v e s tig a to rs .
C om p arativ ely l i t t l e work h a s been done c o n c e rn in g m ic e lle
s t r u c t u r e o f q u a te rn a ry ammonium s a l t s .
Bodecylammonium c h lo ­
r i d e and s e v e r a l a l k y l trlm e th y la a m o n iw brom ides have r e c e iv e d
n e a r ly a l l th e a t t e n t i o n ( 5 , 6 ) .
S o lu tio n s o f th e s e s a l t s show
a b ru p t changes i n t u r b i d i t y a t th e c r i t i c a l c o n c e n tr a tio n ( th e
p o in t a t w hich m ic e lle s b e g in to form i n r e l a t i v e l y g r e a t num­
b ers) .
When in o rg a n ic s a l t s w ere added c o n ta in in g th e an io n i n
common w ith t h a t o f th e d e te r g e n t, th e c r i t i c a l c o n c e n tr a tio n
d e c re a se d and th e m o le c u la r w eig h t o f th e m ic e lle s in c r e a s e d .
The k in d or c h a rg e of th e c a tio n o f th e added In o rg a n ic s a l t
ap p e ared in c o n s e q u e n tia l.
T h is , o f c o u rs e , i s n o t s u r p r i s in g
s in c e p o s i t i v e l y c h a rg e d p a r t i c l e s would be r e p e l l e d from th e
m ic e lle w h ile th e an io n would b e a t t r a c t e d .
These e x p e rim e n ta l
r e s u l t s a r e In agreem ent w ith t h e o r e t i c a l e x p e c ta tio n s s in c e
th e f r e e energy of fo rm a tio n o f th e m ic e lle would be d e c re a se d
by th e p re s e n c e o f gegen io n s , i . e . , l e s s work would be r e ­
q u ir e d t o b r in g lo n g c h a in io n s to g e th e r .
lHie e f f e c t w ith in
l i m i t s becomes more pronounced w ith f u r t h e r in o r g a n ic s a l t ad­
11
d itio n .
A ccording to th e l i t e r a t u r e c i t e d above, d e te r g e n t Iona
a r e h e ld to g e th e r I n th e m ic e lle by van d er W aal’ s f o r c e s be­
tween n e ig h b o rin g h y d ro carb o n c h a in s .
The m ic e lle s i z e I s lim ­
i t e d by th e r e p u ls io n o f th e p o s i t i v e l y ch arg ed monomer h e a d s .
The m ic e lle sh o u ld I n c r e a s e I n s i z e up to th e p o in t where th e
energy l i b e r a t e d by th e sy stem , when lo n g c h a in s come to g e th e r .
I s b a la n c e d by th e work r e q u ir e d to overcome r e p u ls i v e f o r c e s
betw een th e p o la r h e a d s .
Debye (5 ) and o th e rs h av e c o n s id e re d
q u a n t i t a t i v e l y th e e n e r g e tic s o f a m ic e lle sy stem , and have
shown t h a t a m ic e lle w ith h y d ro carb o n c h a in s a lig n e d and th e
p o la r ends o r ie n te d tow ard th e w a te r phase I s f e a s i b l e .
A va­
r i e t y o f c o n f ig u r a tio n s f o r such an a g g re g a te I s p o s s i b le ; th e
m ost p ro b a b le I n c lu d e a sp h e re I n w hich h y d ro carb o n t a i l s occu­
py th e i n t e r i o r , a d is k sandw ich two m o le cu les t h i c k , and a ro d
o f c i r c u l a r c r o s s - s e c t i o n and a r a d iu s eq u al t o th e le n g th of
th e o rg a n ic I o n .
H ydrocarbon c h a in s o f tw e lv e carb o n s w ere s e le c te d I n t h i s
stu d y b e c a u se p re v io u s work (3) w ith a s e r i e s o f alkylammonium
brom ides in d ic a t e d t h a t good r e s u l t s c o u ld b e ex p e c te d w ith
them*
12
I I I . PREPARATION OP DETERGENTS (17)
The compounds o f t h i s s tu d y co m p rise f o u r s e r i e s w ith gen
o r a l fo rm u la e :
Ci 2-N-H w C I m
A
c I 2-N-Rw C iw
R
c I 3-N-Rw O iw
k
(II)
(I)
(III)
CH3
012-” " CH5 H")X<" )
OH3
(IV)
w here R = hydrogen ( in ( I ) o n ly ) , m e th y l, e t h y l , n - p ro p y l, o r
n - b u ty l and X = i o d id e , b ro m id e, o r c h l o r id e .
I . S e r ie s ( I )
The main r e a c tio n s f o r p r e p a r a tio n a r e :
H
c Ig-N-H
^12“ ®**
Br
[ l]
&
H
C i g - N - R ^ S r ^ i - K O R c I 2-N-H +
R
0
+
B r(" i- HgO
[2]
R
-N-H -h HCl ------ w12 I
R
H
i W
(-)
C -N-H
Cl
12 I
R
[5]
The g e n e ra l p ro c e d u re f o r p r e p a r a tio n o f t h i s s e r i e s went
a s f o llo w s .
Dedecyl bro m id e, a l k y l am ine, and e th y l a lc o h o l
13
( a b s o l u t e ) , i n th e mole r a t i o o f 1 * 2 :3 , were heated. 12-16 h o u rs
i n a s e a le d g la s s tu b e a t 130o-1 4 0 ° c e n tig r a d e .
I t i s im por­
t a n t to have enough e th y l a lc o h o l p r e s e n t so t h a t f o r a a tio n o f
a dodecylalkylam m onl 13» brom ide p r e c i p i t a t e , w hich m ight decom­
p o se a t t h i s te m p e ra tu re , i s p re v e n te d .
b een h e a te d , e th y l e th e r was add ed .
A fte r th e m ix tu re h ad
T his cau sed th e d o d e c y la l-
k y I ammonium brom ide t o c r y s t a l l i z e o u t o f s o l u t i o n .
The e th e r
m ix tu re was f i l t e r e d and th e c r y s t a l l i n e p r e c i p i t a t e c o l l e c t e d .
The p r e c i p i t a t e was th e n d is s o lv e d i n e th y l a l c o h o l.
Concen­
t r a t e d p o ta ssiu m h y d ro x id e , whan added to th e a lc o h o lic s o lu ­
t i o n , prod u ced two im m isc ib le l a y e r s .
The am ine la y e r was sep ­
a r a t e d from th e aqueous l a y e r , d r ie d o ver sodium , and vacuum
d is tille d .
The f r a c t i o n o f th e d i s t i l l a t e c o n ta in in g th e do-
d e c y la lk y la m in e was c o l l e c t e d .
o d o r le s s l i q u i d s .
The am ines w ere c o l o r l e s s ,
H y d ro c h lo ric a c id i n o n e - h a lf m ole excess
was added t o a lc o h o lic s o lu tio n s of th e am ines t o g iv e th e dodecylalkylaam onium c h l o r i d e s .
R epeated p r e c i p i t a t i o n and s o l ­
v a tio n w ith e th y l e th e r and e th y l a lc o h o l r e s p e c t i v e l y gave
w h ite , f la k y c r y s t a l s o f th e n e c e s s a r y p u r i t y .
B efo re s t o r i n g
o v er PgO^, th e d e te r g e n ts w ere vacuum d e s ic c a te d .
However, th e y i e l d was d im in ish e d b ec au se of th e s id e r e ­
a c t ! ons *
H
I (+) ( - )
C1 o-H-H
Br
k
H
(-)
H
I
C12-N-R
[4]
14
H
H
I
C12 -N-R -h C12
I
(+)
(-)
[5 ]
The p ro d u ce o f r e a c t i o n I5] i s e a s i l y s e p a r a te d from th e
m onododecylalkyl am ine "because o f th e g r e a t d if f e r e n c e in b o i l ­
in g p o i n t s •
No a tte m p t was made to p re p a re th e d id o d ecy lam in e
c h lo r id e s a l t s .
Dodecyl brom ide was p r e f e r r e d as a s t a r t i n g m a te r ia l to
dodecyl io d id e b e c a u se o f ex p en se, and p r e f e r r e d to dodecyl
c h lo r id e b e c a u se th e r e a c t i o n r a t e c o n s ta n t f o r r e a c tio n [ l ]
was found t o in c r e a s e w ith in c r e a s in g m o le c u la r w eig h t of do­
decyl h a lid e .
P ro lo n g ed h e a tin g in c r e a s e d th e y i e l d of th e d l -
do d ecy l s a l t , and c o rre s p o n d in g ly d e c re a se d th e monododecyl
s a l t y ie ld .
An I n c r e a s e i n te m p e ra tu re o v er a lo n g p e rio d of
tim e c a u se d d e c o m p o sitio n .
However, a good y i e l d co u ld be ob­
ta in e d w ith v e ry l i t t l e d eco m p o sitio n by h e a tin g th e r e a c ta n t s
i n a c lo s e d tu b e from one to two h o u rs a t 190o-200°C .
2 . S e r ie s ( I I )
The m ain r e a c tio n s ( I ) f o r p r e p a r a tio n and g e n e ra l e x p e ri­
m e n tal p ro c e d u re a r e s im ila r to th o s e f o r S e r ie s ( I ) .
However,
th e o c c u rre n c e o f a s id e r e a c tio n c o rre sp o n d in g t o r e a c tio n [5 ]
to form a tr ia l k y ld o d e c y l s a l t i s n o t so l i k e l y .
T h e re fo re ,
th e s t a r t i n g m a te r ia l s were u s u a lly h e a te d from 180°-190®C. I n
a c lo s e d tu b e f o r f o u r to f i v e h o u r s .
E th y l a lc o h o l (a b s o lu te )
15
was xised as s o lv e n t•
Bnoxi^tx e th y l a lc o h o l must toe p r e s e n t to
p re v e n t any c r y s t a l l i z a t i o n , s in c e d eco m p o sitio n would occur a t
h ig h te m p e r a tu r e s .
I f c r y s t a l l i z a t i o n can n o t be p r a c t i c a l l y
p re v e n te d , o r I f d eco m p o sitio n o c c u rs i n s o l u t i o n , th e n th e r e ­
a c tio n sh o u ld b e c a r r i e d o u t a t a te m p e ra tu re below th e decom­
p o s i t i o n p o in t o f th e d e s ir e d p ro d x ict.
However, a t low er tem­
p e r a tu r e s th e r e a c t i o n r a t e i s axich slo w e r.
I n p r e p a r in g th e compoxaxds o f t h i s s e r i e s , i n d i s t i n c t i o n
t o th o s e o f S e r ie s ( I ) , ex cess d ed e cy l brom ide ( a s w e ll as ex­
c e s s d i a l k y l am ine) c o u ld b e e lim in a te d e a s i l y I n th e vacuum
d is tilla tio n .
A lso , th e compounds of S e r ie s ( I ) w ere more e a s­
i l y p u r i f i e d th a n d o d e c y ld ip ro p y l- and dodecyldibutylam m onliaa
c h lo rid e .
In f a c t , th e l a t t e r two d e te r g e n ts c o u ld n o t be s u f ­
f i c i e n t l y p u r i f i e d to j u s t i f y stu d y by l i g h t s c a t t e r i n g meth­
o d s.
A lthough th e a p p a re n tly p u re am ines w ere p re p a re d , i t i s
th o u g h t d eco m p o sitio n oeoxarred due to th e h ig h te m p e ra tu re a t
w hich th e c lo s e d tu b e r e a c tio n was c a r r i e d o u t.
I t is f e l t
t h a t th e d l f f I c x ilt le s c o u ld have b een overcome by p r e p a r a tio n
a t low er te m p eratx ire s.
5 . S e r ie s ( I I I )
The main r e a c t i o n i s :
R
c I 2-G ! -MIR3
Ci2 -N-R w O it - 1
te l
The d e te r g e n ts o f t h i s s e r i e s w ere e a s i l y p re p a re d by mix-
16
In g SbOH ( a b s o l u t e ) , d o decyl c h l o r id e , and t r l a l k y l amine I n
th e mole r a t i o 2:1*2#
The tr lm e th y l s a l t (23) was o b ta in e d by
r e f l u x i n g a p p r o p r ia te r e a g e n ts f o r two h o u rs I n a d r y - ic e
c o o le d system #
R efltoclng f o r a week produced v e ry l i t t l e do-
d e c y l t r l e th y l o r d o d e o y ltrlp ro p y l s a l t #
Yet h e a tin g th e r e a ­
g e n ts I n a c lo s e d tu b e f o r one h o u r a t 160o-170°C# or f o r 24-28
h o u rs a t QO0-IOO0C, gave alm o st q u a n t i t a t i v e y i e l d s .
S in ce th e
end p ro d u c t of r e a c t i o n [ 6 j I s th e d e s ir e d s a l t , th e c lo s e d
tu b e m ix tu re was d i r e c t l y p u r i f i e d .
C r y s t a l l i z a t i o n o c c u rre d
when e th y l e th e r was added to th e a lc o h o lic m ix tu re .
A check
on p u r i t y a t t h i s p o in t r e v e a le d a p ro d u c t of o n ly s l i g h t con­
ta m in a tio n .
S u b seq u m t p u r i f i c a t i o n o f th e t r i a l k y l ammonium
s a l t s w ith e th y l a lc o h o l and e t h e r , a lc o h o l and b en zen e, o r
e th y l a c e t a t e and d ry i c e r e s u l t e d I n c o n s id e r a b le decomposi­
tio n .
F i n a l l y , th e t r i e t h y l s a l t was p u r i f i e d o n ly a f t e r sev ­
e r a l c a r e f u l r e c r y s t a l l i z a t i o n s w h erein th e te m p e ra tu re n ev e r
exceeded f i f t y d e g r e e s .
The p u r i f i c a t i o n of th e t r l p ro p y l and
t r i b u t y l s a l t s was n o t com pleted b e c a u se th e s e compounds were
fo u n d to be to o I n s o lu b le I n w a te r f o r l i g h t s c a t t e r i n g w ork.
An a tte m p t to p re p a re tr le th y ld o d e c y !ammonium c h lo r id e a c ­
c o rd in g to th e m ethod o f K ra ft (18) f o r dodecyltrlethylam m onium
io d id e was u n s u c c e s s f u l.
CHgCH3
C12-N + CH3CH2Cl
OH2OH3
The r e a c t i o n .
O yn3
C i2-H-CH2CH3
OH2CH3
^
Cl
(-)
173
17
d id n o t o ccu r to g r e a t e x te n t#
T his f u r t h e r I l l u s t r a t e s th e
r e l a t i v e r e a c t i v i t y betw een a lk y l c h l o r id e s , b ro m id e s, and i o ­
d id e s s in c e a lk y l io d id e s seem t o r e a c t e a s i l y .
P robably th e
dod e c y l t r l p ro p y l and dod e c y lt r i b u t y l s a l t s co u ld have been pu­
r i f i e d by v e ry c a r e f u l r e c r y s t a l l l z a t l o n a a t low te m p e ra tu re .
A p o s s i b le d eco m p o sitio n r e a c t i o n c o u ld be*
R
I (+)<->
C i2-H-R
Cl
H
C10-C "
R
I
(+ ) ( - )
CH2 4 - HH-R
Cl
[81
R
An o n io n - lik e o d o r, c h a r a c t e r i s t i c of a lk e n e s , was n o tic e d
i n some c a s e s , v i z . , t r l p r o p y l , d ib u ty l , d ip r o p y l.
A lso, th e
p e r c e n t c h lo r id e in c r e a s e d w ith each c r y s t a l l i z a t i o n , th e re b y
i n d i c a t i n g d e c o m p o sitio n .
4 . S e r ie s (IV)
E ith e r dodecyltrim ethylam m onium brom ide o r d o d e c y ltrim e th ylamaonlum c h lo r id e was d is s o lv e d i n 90 p e r c e n t e th y l a lc o h o l,
t r e a t e d w ith m o ist Ag2 O I n s l i g h t mole e q u iv a le n t e x c e ss .
The
r e s u l t i n g m ix tu re was s t i r r e d I n t e r m i t t e n t l y o v er a tw o-hour
p e r io d and f i l t e r e d th ro u g h a s i n t e r e d g l a s s , f i n e f i l t e r to
g e t r i d of AgBr*
The f i l t r a t e was n e u t r a l i z e d w ith th e d e s ir e d
a c id , l . e . , HCl o r H I, end e v a p o ra te d .
O r ig in a lly trlm e th y ld o -
decylam moniua brom ide and c h lo r id e were made and p u r i f i e d by
th e m ethods g iv en u n d er S e r ie s ( I I I ) .
Hence, th e c h lo r id e s a l t
was produced by two in d e p e n d e n t m ethods.
s a l t e x h ib ite d o b se rv a b le d e liq u e s c e n c e .
Only th e c h lo rid e
18
5 . G eneral Remarks
Halogen d e te rm in a tio n In a l l c a s e s o f f e r e d th e most conven­
i e n t method f o r d e te rm in in g p u r i t y .
d u re was d ev e lo p ed .
A m o d ifie d V olhard p ro c e ­
A sam ple o f d e te r g e n t, e q u iv a le n t to 15 to
25 c c . CXlNAgMOy was w eighed o u t.
10-15 c c . o f w a te r, 3-5 o c .
o f d i l u t e HNOg, and s u f f i c i e n t BtOH to produce a c l e a r s o lu t io n
( u s u a lly 5-10 c c .) w ere ad ded .
A f te r a 3-5 c c . ex cess of
AgN03 > f e r r i c ammonium s u l f a t e i n d i c a t o r , and 10-15 c c . of n i ­
tro b e n z e n e w ere added, th e s o lu t io n was mixed v ig o ro u s ly to e f ­
f e c t a d s o rp tio n o f n itro b e n z e n e by AgCl,
Then KSCN was t i t r a t ­
ed i n t o th e m ix tu re to th e f i r s t p e r c e p tib le c o lo r change
( c l e a r t o f a i n t o r a n g e )•
W ith t h i s method no foam ing o c c u rs ,
n itro b e n z e n e i s n o t e m u ls if ie d , and th e end p o in t i s sh a rp and
s ta b le .
A lso , f a r l e s s tim e i s r e q u ir e d f o r an a n a ly s is th a n
w ith m ethods u s in g g ra v im e tric a n a l y s i s .
For brom ide and i o ­
d id e s a l t s , n itro b e n z e n e i s n o t n eed ed .
Dodecylammoniurn c h lo r id e was o b ta in e d by t r e a t i n g dodecyl
am ine w ith c o n c e n tr a te d h y d ro c h lo ric a c id a c c o rd in g to th e
m ethod of R a ls to n and H oerr ( 2 2 ).
D e te rg e n ts in s o l u b le i n w a te r a t room te m p e ra tu re were
c r y s t a l l i z e d from BtOH by th e a d d itio n of HgO as w e ll as e t h e r .
A ll w ere d r ie d o ver
u re d .
b e f o r e p h y s ic a l c o n s ta n ts were meas­
R e s u lts a r e ta b u la t e d i n T able I .
M e ltin g p o in ts w ere
o b sc u re d by d ec o m p o sitio n , b u t th e deco m p o sitio n p o in ts were
r e p r o d u c ib le w ith in
"LV0C. Only th o s e K ra ft p o in ts above 30®C.
COKPOIE D
I • Dodecyl c h lo r id e
2*Dedecylafflmonltna c h lo r id e
3 . D odecyltrlm ethylaB ian c h i o r .
4. D ed ecy ld lethylamm. c h lo r id e
5 . D odecylaethylaina. c h lo r ld e
S .D odecylethylanm . c h lo r id e
7 . Dedecylpropylafflm. c h lo r id e
8 . DodecyIbutylam m . c h lo r id e
9 . D odecyltrlm ethylam m ehraelde
1 0 . Dodecyltrlm ethylarara. I o d id e
1 1 . D ed ecy laeth y l amine
1 2 . D ed ecy leth y l amine
13. D odecylpropyl amine
1 4 . D odecylhutyl amine
1 5 . D o d eo y ld iaeth y l amine
1 6 . D odecyldle th y l amine
1 7 .D o d ecy ld lp ro p y l amine
1 8 . D o d ec y ld lh u ty l amine
% H alo% H alo- gen, exg e n .th e - p e r i o r e t i e a l m en tal
1 6 .0 6
13.47
12 .8 3
1 5 .0 7
1 4 .2 3
13.47
12.79
1 2 .9 5
3 5 .7 6
B o ilin g
P o in t
i n Deg re e s C.
P re ssu re
in mm.
o f Hereu ry
134-136
15
1 6 .0 3
13.51
12.81
15.09
14.26
33 .5 0
12.77
12.92
35.72
Deoomp e a ltio n
P t. i n
°±76C.
139
151
73
82
99
87
92
147
125
113-116
121-124
or
142-144
146-149
155-156
124-127
132-134
164-167
170-172
7-8
5
er
15
11-12
10-11
6-10
5-7
11-12
6-9
—
K ra ft
P o in t
in
°C.
35
45
65
43
a r e re c o rd e d
TABLE I
P h y s ic a l C o n sta n ts of S y n th e siz e d Prodia c ts and Ile a g e n ts
20
6» R eagento
P u r ity and n o t y i e l d was th e main c r i t e r i o n i n p re p a rin g
th e d e t e r g e n ts .
Dodecyl c h lo r id e was p re p a re d from dodecyl
a lc o h o l u s in g Lucas R eag o n t.
c a l.
Y ie ld was 65 p e r c e n t t h e o r e t i ­
Dodecyl brom ide and some d o d ecy l c h lo r id e w ere o b ta in e d
from Columbia Chem ical Company and were f r a c t i o n a l l y d i s t i l l e d
u sin g a column o f 25 t h e o r e t i c a l p l a t e s and a r e f l u x r a t i o of
l:2 5 e
Dodecyl c h lo r id e f r a c t i o n s were c o l le c te d a t 134-136°C.
a t 15 am, of m ercu ry , and dodecyl brom ide f r a c t i o n s a t 147149°C. a t 15 mm. o f m ercu ry ,
The amines ( b e s t grad e Eastman Kodak) were d i s t i l l e d or
vacuum d i s t i l l e d depending on b o ili n g p o in ts .
M ethyl, dim eth­
y l , and e th y l amine were o b ta in e d as aqueous s o l u t i o n s .
They
were e a s i l y s e p a r a te d from th e EgO by d i s t i l l a t i o n in to a tu b e
c o o le d by dry i c e .
However, th e 40 p e r c e n t aqueous m ethyl
amine s o lu t io n , when added d i r e c t l y to th e d o d ecy l am in e-alc o ­
h o l m ix tu re and m a in ta in e d a t 225°C. i n a c lo s e d tu b e , gave a
good y i e l d of d o decyl m ethyl am ine.
The a b s o lu te a lc o h o l and DSP e th e r were f r e s h l y d i s t i l l e d
b e f o r e u se .
Dodecyl amine ( b e s t g rad e M atheson), h y d ro c h lo ric
a c id , h y d rlo d ic a c id , and h y d r o f lu o r ic a c id , a l l TJSP, w ere n o t
fu rth e r p u rifie d .
Bureau o f S tan d a rd s su c ro se (S ta n d a rd Sample
17) was n o t f u r t h e r p u r i f i e d .
R affan o se p e n ta h y d ra te d (+ ), CP,
was o b ta in e d from th e P f a n s tie h l Chemical Company and f u r t h e r
p u r i f i e d by s e v e r a l r e c r y s t a l l i z a t i o n s from f r e s h , d o u b ly -d ls -
21
t i l l e d w ate r to e lim in a te su c ro s e (1 6 )•
The p u r i f i e d r a f f a n o s e
p e n ta h y d ra te was d r ie d a t 75®C# under m oderate vacuus.
22
I V . APPARATUS
A d e t a i l e d d e s c r ip tio n o f a s im ila r l i g h t s c a t t e r i n g i n ­
stru m e n t has been g iv en elsew h ere ( 6)«
The e s s e n t i a l f e a t u r e s
o f t h i s sim p le f lu o r im e te r ty p e in s tru m e n t a r e i l l u s t r a t e d in
F ig u re I ,
The l i g h t so u rc e i s a 100 w a tt, low p r e s s u r e m ercury
a rc {QKAH-4).
A b a l l a s t lamp s e rv e s to s t a b i l i z e th e o u tp u t
o f th e s o u rc e .
The in c id e n t l i g h t p a s se s th ro u g h a le n s system ,
w hich p rod u ces a p a r a l l e l beam, and a m onochrom atizin g f i l t e r
e
(4358 A) b e f o r e e n te r in g th e r e c ta n g u la r s c a t t e r i n g c e l l . L ig h t
s c a t t e r e d p e r p e n d ic u la r to th e p rim ary beam i s r e f l e c t e d by a
m ir r o r to a m u l t i p l i e r photo tu b e (RCA 1P 21),
The i n t e n s i t y o f
th e s c a t t e r e d beam i s p r o p o r tio n a l to th e d e f l e c t i o n o f th e
n e e d le o f a s e n s i t i v e g alv an o m eter co n n ected d i r e c t l y to th e
m u l t i p l i e r photo tu b e .
Because o f th e h ig h s e n s i t i v i t y of th e
1P21, l i g h t s h ie ld in g i s e s s e n t i a l .
Hence, th e pathway from
th e m irro r to th e 1P21 i s r e g u la te d by a s h u t t e r .
The e n t i r e
chamber c o n ta in in g th e c e l l l a b la ck en e d to keep r e f l e c t i o n s a t
a minimum.
A l i g h t t r a p p re v e n ts th e tr a n s m itte d l i g h t from
c a u sin g s p u rio u s r e a d in g s .
A t i g h t - f i t t i n g l i d , form ing th e
to p o f th e in s tru m e n t, p ro v id e s a c c e s s to th e cham ber.
A s in g le
c e l l o f fu s e d p y rex g la s s , ap p ro x im a te ly 7& cm, h ig h and o f
sq u a re c r o s s - s e c t i o n ab o u t 3 .6 s q . cm ., was used f o r s o lu tio n
in v e s tig a tio n s .
The m ost p r a c t i c a l v o lta g e f o r o p e ra tio n was ab o u t 90-100
v o l t s per dynode s ta g e of th e 1P21 tu b e .
At t h i s v o lta g e , se n -
23
< - » H-TDHOGfcN
SIDE VIEW
'
FILTER APPARATUS
ULTRA FINE FILTER
RUBBER STOPPER
V
RUBBER TUBING
D
FURROWED TOP
STAND
CELL
HOLDER
FIG. 3
SCHEMATIC VIEW OF
90°
D ---- r
LIGHT SCATTERING
6 8
A
AM- 4
B
CONDENSING
C
FILTER
D
DIAPHRAGM
E
COLLIMATING LENS
F
CHAMBER
G
CELL
H
MIRROR
I
IP E I TUBE
J
K
LAMP
TOP
VIEW
LENS
D IF F E R E N T IA L
E Z
REFRACTOMETER
SYSTEM
A AH* 4 L A M P
B PINHOLE
C EILTER
D
LIGHT TRAP
SLIT
E SIMPLE
F CELL
G CROSS
AMMETER
AND
C I------------1
B ------------A
O
FIG.2
LENS
HAIRS
E Y E PI EC E
24
s i t i v l t y i s s u f f i c i e n t t© m inim ize e r r o r in g alvanom eter re a d ­
in g s , y e t n o t so g r e a t a s to c a u se n o tic e a b le photo tu b e d e te ­
r i o r a t i o n w ith tim e o r to d im in ish s t a b i l i t y o f r e a d in g s .
At
any v o lta g e , s e n s i t i v i t y w i l l d e c re a s e somewhat d u rin g th e du­
r a t i o n ( u s u a lly ab o u t two h o u r s ) o f o p e r a tio n .
However, th e
i n i t i a l s e n s i t i v i t y i s re g a in e d when th e in s tru m e n t i s n o t used
f o r ab o u t f i v e h o u rs .
B efore each t r i a l , when u sin g th e s ta n d ­
a r d , th e n e e d le d e f l e c t i o n o f th e g alvanom eter was always ap­
p ro x im a te ly 35 p e r c e n t of th e f u l l s c a le r e a d in g .
The power
su p p ly c i r c u i t f o r th e photo tu b e i s t h a t recommended by RCA.
I t employs a f u ll- w a v e r e c t i f i e r w ith v o lta g e d iv id e r f o r sup­
p ly in g DC v o lta g e s to th e 1P21 I n a p p lic a tio n s c r i t i c a l as to
hum m o d u la tio n .
R e f r a c tiv e in d e x r e l a t i o n s w ere c o n v e n ie n tly d eterm in ed
w ith a d i f f e r e n t i a l r e f r a c to m e te r (8) s c h e m a tic a lly shown in
F ig u re 2 (n o t drawn to s c a l e ) .
The l i g h t beam, o r ig in a t in g
from a m ercury vapor a rc (QE AH-4), p a s se s th ro u g h i n su c c e s­
s io n a p in h o le , m onoohrom atizing f i l t e r , a s l i t , a sim p le le n s ,
th e c e l l , a n o th e r sim p le le n s , and f i n a l l y , th e e y e p ie c e .
The
s l i t i s lo c a te d a t th e f o c a l p la n e o f th e f i r s t l e n s ; th e c r o s s
h a i r s of th e ey e p ie c e a t th e f o c a l p la n e o f th e seco n d .
e y e p ie c e i s o f th e f i l a r m icrom eter ty p e .
The
The d is ta n c e from
c e l l to c r o s s h a i r s i s a p p ro x im a te ly HO cm.
The r e f r a c to m e te r c o n s is ts o f two com partm ents s e p a ra te d
by a g la s s b a r r i e r .
To p re v e n t e v a p o ra tio n a m e ta l to p i s
25
p la c e d over th e c e ll*
C o n tact w ith th e o u te r a id e s p re v e n ts
d i f f i c u l t i e s due to c a p i l l a r y a c t i o n .
26
V.
EXPERIM331TAL METHODS
S o lu tio n s were s tu d ie d i n th e fo llo w in g m anner.
Samples
o f th e s u r f a c t a n t s w ere w eighed o u t to th e c l o s e s t m illig ra m ,
p la c e d i n 25 c c . p y rex v o lu m e tric f l a s k s , and d is s o lv e d i n wa­
te r.
The s o lu t io n s were d i l u t e d a lm o st to 25 c c . , p la c e d i n a
c o n s ta n t te m p e ra tu re atm osphere an d , f i n a l l y , d i l u t e d e x a c tly
to 25 c c .
Each s o lu t io n was f i l t e r e d th ro u g h a p y re x , u l t r a -
f i n e , f r i t t e d g la s s fu n n e l d i r e c t l y i n t o th e l i g h t s c a t t e r i n g
c e ll.
P re s s u re f i l t r a t i o n was u sed to av o id fo am in g .
Hydrogen
gas was used as th e so u rc e o f p r e s s u r e —from 2 I b s . / s q . in c h
f o r most d e te r g e n t s o lu tio n s to 10 I b s . / s q . in c h f o r c o n c e n tra t­
ed s u c ro s e and r a f f a n o s e s o l u t i o n s .
s e t-u p .
F ig u re 3 i l l u s t r a t e s th e
A fu rro w ed oap was g lu e d to th e top of th e la r g e ru b ­
b e r s to p p e r , w hich f i t t e d sn u g ly i n t o th e f i l t e r f u n n e l.
Hy-
drogen gas p a s se d d i r e c t l y to th e s o lu t io n from a ta n k th ro u g h
an opening i n th e cap and ru b b e r s to p p e r .
A fte r f i l t r a t i o n ,
th e c e l l was p la c e d i n th e c e l l h o ld e r w ith th e same o r ie n ta ­
t i o n each tim e .
Two b a l l b e a r in g s , p r o je c tin g from two s id e s
w ith in th e c e l l h o ld e r , k e p t th e c e l l i n th e same p o s it io n each
tim e .
A ll e x p e rim e n ta l work was done a t 30°C. u n le s s o th e rw ise
s ta te d .
R a re ly a f t e r f i l t r a t i o n o f a d e te r g e n t s o lu t io n would bub­
b le s form (betw een th e s c a t t e r i n g c e l l - l i q u i d i n t e r f a c e ) or
su d sin g o c c u r.
Bubbles were e a s i l y removed w ith a s t i r r i n g ro d
o r by p h y s ic a l a g i t a t i o n .
I t was n e c e s s a ry to do t h i s to p ro ­
27
v e n t r e f l e c t i o n s from th e m e n iscu s, and d i f f r a c t i o n s and r e ­
f l e c t i o n s due t o b u b b le s .
M easurem ents a t e le v a te d te m p e ra tu re s were c a r r i e d o u t by
h e a tin g th e im m ediate su rro u n d in g s to th e d e s ir e d te m p e ra tu re .
The s o lu t io n s were made up a t th e e le v a te d te m p e ra tu re s .
Be­
f o r e and a f t e r s c a t t e r i n g re a d in g s w ere made, th e te m p e ra tu re
o f th e s o lu t io n was ta k e n .
The d if f e r e n c e was u s u a lly 1°-2®C.
A more d e s ir a b le p ro c e d u re f o r e le v a te d te m p e ra tu re s tu d ie s
would have been to make t u r b i d i t y m easurem ents u s in g a c e l l
w ith a su rro u n d in g chamber h e a te d by r e s i s t a n c e w ir e s .
L ig h t s c a t t e r i n g re a d in g s w ere ta k e n im m ed iately fo llo w in g
filtra tio n .
The i n t e n s i t y o f th e l i g h t s c a t t e r e d from a s o lu ­
t i o n was compared w ith th e i n t e n s i t y o f l i g h t s c a t t e r e d from a
p o lis h e d I n c i t e b lo c k ( 2 ) .
R eadings on th e s ta n d a r d were made
j u s t b e fo re and a f t e r th o s e made on a s o lu t io n .
t e r i n g was m easured.
Only 90° s c a t ­
Ten s o lu tio n s r e q u ir e d ab o u t two h o u rs f o r
a com plete r u n .
R e fe re n ce was made to th e l u c l t e b lo c k f o r two re a s o n s :
(a) S ta n d a r d iz a tio n o f th e l i g h t s c a t t e r i n g in s tru m e n t es­
s e n t i a l l y means i n t h i s stu d y d e te rm in in g th e " e f f e c t iv e " t u r ­
b i d i t y o f th e I n c i t e b lo c k .
Hence com parison o f g alvanom eter
re a d in g s o f a s o lu t io n w ith th e I n c i t e b lo ck gave d i r e c t l y th e
t u r b i d i t y o f th e s o l u t i o n .
(b) A d e c re a s e i n i n t e n s i t y o f th e l i g h t so u rc e w ith tim e ,
and a d e c re a s e i n s e n s i t i v i t y o f th e 1P21 tu b e .
28
The l i g h t s c a t t e r i n g in s tru m e n t was s ta n d a r d is e d in th e
fo llo w in g manner*
S c a tte r in g m easurem ents w ith aqueous s o lu ­
tio n s o f p u r i f i e d s u c ro s e and w ate r ( s o lv e n t) w ere made.
The
galv an o m eter d e f le c tio n due to w a te r, d iv id e d by th e d e f le c tio n
due to l u c i t e b lo c k , was s u b tr a c te d from th e d e f le c tio n due to
th e s o lu tio n d iv id e d by b lo c k d e f le c tio n *
T his gave KT•
K is
th e r e c i p r o c a l t u r b i d i t y ( e f f e c t i v e ) o f th e l u c i t e b lo c k , and T
i s th e s o lu t io n t u r b i d i t y minus w a te r tu r b id ity *
As p r e v io u s ly
s t a t e d , th e g alvanom eter d e f le c tio n s a r e p r o p o r tio n a l to l i g h t
s t r i k i n g th e 1P21 tu b e , l . e . , th e l i g h t s c a t t e r e d a t 90e to th e
in c id e n t beam.
HC/T
v s.
S in ce HC/T = (l/M )4-BC, e x tr a p o la tio n o f th e
C p l o t to z e ro c o n c e n tr a tio n y ie ld s l/M .
V T / c=o
M
\ KT / c = o
M
Only two unknowns need to be d e te rm in e d .
ta in e d from a cu rv e o f (C/KT)
vs.
C ( g / c c . ) . (See F ig u re 4 .)
was d eterm in ed u sin g th e r e l a t i o n s
2
32 T r V
SN A*
/W
V
'
e
(C/KT) q - q I s ob­
)
/
H
29
(Ji-Jio)A' was o b ta in e d from d i f f e r e n t i a l r e f r a c to m e te r data#
The d i f f e r e n t i a l r e f r a c to m e te r was s ta n d a r d iz e d w ith s u c ro se ,
©
u sin g b lu e l i g h t (4358 A)«
S u cro se s o lu tio n s w ere p re p a re d
where b o th w eig h t p e r c e n t s o lu t e and grams p e r co* were r e ­
c o rd e d ,
The s c a le d e f le c tio n o f each s o lu t io n , minus d e f le c ­
t i o n due to w a te r, was r e f e r r e d to as ZX R,
A ccording to Mc­
C artney (2 1 ), th e r e l a t i o n (fi-p0 ) g a g s " cw x IO**4 a t 20°C,
h o ld s f o r s u c ro s e f o r th e sodium D l i n e .
R e f r a c tiv e Index of
s o lu t io n and w a te r a r e d e s ig n a te d p and p e r e s p e c t i v e l y , Cw i s
c o n c e n tr a tio n in w eig h t p er c e n t s u c ro s e ,
m ula,
= A 4- ( B /X 2 )# (ja-ji@) a t X =
S in c e
Frcrni th e Cauchy f o r ­
4358 A can be c a lc u l a te d .
J i = A' 4 - B '/ X 2# and ya0 = A" 4 " B " /X 2
th e re fo re
2
Ji-Ji0 sa A 4 - B /X , i n w hich A = I A 1-An and B = B 1-B n,
A ccording to Hallwache ( 15 )
(/1- / 10 ) 486 !
(/^JaO)6563
0124 (/""Po)5893
U t i l i z a t i o n o f th e s e two r e l a t i o n s h i p s e n a b le s one to g e t
th e fo llo w in g *
20°
20°
(/*-/*©) 4358— I »016 (/1-/10)5893
However, m easurem ents w ere g e n e r a lly made a t 30°C,
H allw achs fo u n d f o r su c ro s e s o lu t io n s t h a t
1 7 .8 °
(/1- / 10)5893 * 9 .5 x IO"*4
5893
For a 10° I n c r e a s e in te m p e ra tu re th e d e c re a s e i n ()i-Jio)5893
30
would be ap p ro x im a te ly ,0095 (P-ZU0 ) gog3 ,
I f we assume (/uwJlO^4358
30®
d e c re a s e I n a s im ila r manner
20°
(P -P 0 ) 4 3 5 8 -
20®
(p -P o )4358 * *0095 (P-Po)4S s s
20°
— (p -P o )4358 (^- - *0095)
20®
= 1 .0 1 6 (P-P 0 ) 68g3 (.9 9 0 5 )
= 1 .0 1 6 (14.51 Cw x 10”4 ) (.9 9 0 5 )
= 1 4 .6 0 x IO"4 Cw
When A r was p l o t t e d a g a in s t Cw, th e l e a s t sq u a re s s lo p e
A V o w = 1 4 .7 2 , o r Cw = A V l 4 .7 2 .
T h e re fo re
30°
(JMNj ) 4 3 6 8 = 9 .9 1 3
=
AR x 10~°
w here AR r e f e r s t o th e re a d in g g iv en by th e r e f r a c to m e te r f o r
p u re s o lv e n t m inus th e re a d in g f o r th e s o lu t io n .
T his i s th e
w orking e q u a tio n f o r th e d i f f e r e n t i a l r e f r a c to m e te r .
To o b ta in H f o r any s o lu t io n , A VC o n ly n eed b e determ ined
s in c e (p -p e )/C = 9.9 1 3 x 1 0 "^ (
AV°)
w here C =r g/oc*
F or s u c ro s e :
C
AR 100
Cw / 9
t i o n a t 30°C.
w here
/* = d e n s ity o f a 1% su c ro se aolu-
T h e re fo re
AR
1 4 .7 2 x 100
= 1 .4 7 4 x 10 3
C "™9 .9 9 5 x lO - 3
and
2
u -u 0
( 4 C
M
=
<». 913 x 1 .4 7 4 x 1 0 " 2 )
_
.0 2 1 3 5
31
Prora th e Lange Handbook ( 6 th e d i t i o n ) , a t 30oC ., f o r HgO,
A
= 5893
fiAIR s 1.3320
4861
4340
1.3360
1.3392
yuVAC =/oAIR x 1.000294
By u sin g t h e e m p iric a l Cauchy fo rm u la a g a in , c o n s ta n ts A
and B can be c a lc u l a te d ;
/I4358 f o r H2O, 3 0 ° C .= 1 .3 3 9 5
T h e re fo re , f o r s u c ro s e ,
A = 4385, tem p. = 30°C ,
and
H = 5.832 x 1 0 -8 .
In F ig u re 4, (C/KT)
vs .
C i s p l o t t e d f o r s u c ro s e , and ex­
t r a p o l a t i o n to C = O gives (C/KT)q s q = 0 .5 6 6 .
From th e sucrose
d e te r m in a tio n , then, Kss 8 .8 9 x IO2 .
S ta n d a r d iz a tio n o f th e l i g h t s c a t t e r i n g in s tru m e n t w ith
r a f f a n o s e p e n ta h y d ra te was done i n th e same manner as w ith su ­
cro se .
P or r a f f a n o s e * SHgO a t SO0C. , H =, 5.832 x IOw6.
F ig u re 4, w here G = O, C/KT = 0 .4 3 1 .
From
The av e ra g e K i s
8 .6 6 x IO2 .
I n o rd e r to c a l c u l a t e m o le c u la r w eig h ts o f m ic e lle s , c e r ­
t a i n assu m p tio n s m ust be made.
c e l l e s c a r r y a c h a rg e .
IDhlike th e su g a r m o le c u le s, mi­
Doty and S te in e r (10) have d is c u s s e d
s c a t t e r i n g due to c o l l o i d a l e l e c t r o l y t e s .
At th e c r i t i c a l con­
c e n t r a t i o n th e c o n c e n tr a tio n o f m ic e lle s i s ex trem ely sm all
( i d e a l l y z e r o ) , and i n t e r a c t i o n n e g l i g i b l e .
Hence m o le c u la r
w eig h ts sh o u ld b e d eterm in ed by e x tr a p o la tio n to th e c r i t i c a l
c o n c e n tr a tio n Ce and n o t to zero c o n c e n tr a tio n (5 ). For a l l
32
LIGHT
FOR
SCATTERING
CURVES
R A F F A N 0 S E -5 H .0
AND
SUCROSE
O
A
C in g/cc x ioo
figure 4
AR VS.
FOR
C g/cc x ioo
figure 5
C
VALUES
SEVERAL
DETERGENTS
33
p r a c t i c a l p u rp o ses I t ca n be assumed t h a t th e s u r f a c t a n t Io n s
a r e u n a s s o c ia te d up t o th e c r i t i c a l c o n c e n tr a tio n , and above
t h i s c o n c e n tr a tio n a l l added d e te r g e n t m o lecu les a g g re g a te to
sh o u ld b e p l o t t e d a s a f u n c tio n o f C.
Debye (3) h a s Bhoim t h a t
a h ig h c o n c e n tr a tio n o f c h a rg e e x i s t s a t th e ends o f th e m i­
c e l l e , presum ably n e a r th e n itr o g e n atom , and th e e x is te n c e of
a h ig h ly c h a rg e d s p e c ie s i n s o lu t io n w ith o u t a t t r a c t i o n of gegen
io n s would be v e ry u n l ik e ly .
We w i l l assume t h a t th e o v e r - a ll
m ic e lle c h a rg e i s v e ry c lo s e to z e r o , t h a t our s o lu t e i s th e
m ic e l le s , and o u r s o lv e n t i s th e s o lu tio n a t th e c r i t i c a l con­
c e n tra tio n .
A l e a s t sq u a re s m ethod h a s been employed i n w hich C0 , M,
C-C0
and th e s lo p e o f th e H —^— v s . C cu rv e a r e sim u lta n e o u sly
o b ta in e d ( 2 ) .
H(C-C0 )
----------- = A4-SC
T
th e n
The b e s t s t r a i g h t l i n e i s r e p r e s e n te d by
w here A = I n t e r c e p t and S i s th e s lo p e .
n
If
2
I
f o r n e x p e rim e n ta l p o i n t s .
By d e te rm in in g
• z - ,=
BC0
'
BA
34
and
»2>i2
and s e t t i n g them eq u a l to z e ro , we g e t th r e e equa­
t i o n s w hich may be so lv e d s im u lta n e o u s ly f o r C0, A, and S»
Ex­
p e rim e n ta l p o i n t s , above th e c r i t i c a l c o n c e n tr a tio n , t h a t ex­
h i b i t non-ancoaalous b e h a v io r (ta k e n from o b s e rv a tio n of a
T v s . C cu rv e) a r e chosen f o r th e c a l c u l a t i o n .
I
M
M=
H(C-C6 )
I
I
A 4" SCo
]
Ca 0
S in c e
A -h SC6 ,
35
T I. RESULTS
HVhen l i g h t s c a t t e r i n g th e o ry was d is c u s s e d i t was p o in te d
o u t t h a t (ti-fio)A ' was assumed to be c o n sta n t#
F ig u re 5 i s a
p l o t of A R v s . C f o r a number o f s u r f a c ta n ts u sed i n t h i s
s tu d y .
The b re a k i n th e r e f r a c t i v e in d e x p l o t of soap s o lu ­
tio n s found by some i n v e s t i g a t o r s (14) was n o t o b serv ed i n t h i s
w ork.
The s lo p e , 0 .1 6 3 , r e p r e s e n te d i n F ig u re 5 i s an av erag e
s lo p e o b ta in e d by l e a s t sq u a re s u sin g p o in ts o b ta in e d from
m easurem ents o f s e v e r a l s u r f a c t a n t s .
The e r r o r in tro d u c e d in
u s in g t h i s s lo p e i n c a lc u l a ti o n o f H f o r a l l s u r f a c ta n ts ap­
p e a rs to be q u ite sm a ll f o r th e c h lo r id e s a l t s , b u t i s n o t j u s ­
t i f i e d f o r th e brom ide and, p e rh a p s . Io d id e s a l t
o f ab o u t 20% I s p o s s ib le ( 3 ) .
By s u b s t i t u t i n g
s in c e an e r r o r
A r/C in th e
w orking e q u a tio n f o r th e d i f f e r e n t i a l r e f r a c to m e te r , H f o r th e
s u r f a c t a n t s was d eterm in ed as 7 .1 6 4 x 10"® a t 30°C.
F or h ig h e r te m p e ra tu re s , o th e r c o n s id e r a tio n s were i n ­
v o lv e d .
C o rre c tio n s were made f o r th e ex p an sio n of th e g la s s
v o lu m e tric f l a s k s .
A c tu a lly , d e n s ity o f w a te r d a ta could have
been u sed to c o r r e c t f o r c o n c e n tr a tio n ch an g es.
The e r r o r i n ­
v o lv ed can s a f e ly be assumed to b e l e s s th a n 0.1 p e r ce n t (2 2 ).
To c a l c u l a t e th e change i n H w ith te m p e ra tu re , th e change in
(p -ji0 )/C would have to be d e te rm in e d .
T his m ight have been
done by u s in g a c e l l f o r th e d i f f e r e n t i a l r e f r a c to m e te r w hich
would keep th e c e l l c o n te n ts a t any h ig h te m p e ra tu re d e s ir e d .
A h o llo w chamber w ith in th e c e l l h o ld e r , to a llo w c o n tin u o u s
36
flo w of h e a te d s o lu t io n , o r an I n s u la t e d c e l l J a c k e t co u ld have
been c o n s tr u c te d .
W ith th e p r e s e n t d i f f e r e n t i a l r e f r a c to m e te r.
M easurem ents can o n ly be made a t room te m p e ra tu re .
The L o re n z-L o re n tz e q u a tio n c o u ld be a p p lie d to c a lc u l a te
{fi~fL0 )/C a t h ig h e r te m p e ra tu re .
c u l t ! et
la c k in g .
'3).
T his would e n t a i l o th e r d i f f i ­
F u rth e rm o re , th e n e c e s s a ry d e n s ity d a ta were
To c o n s id e r H c o n s ta n t w ith te m p e ra tu re sh o u ld i n t r o ­
duce e r r o r w ith in I p e r c e n t a t 30®C., 2 p e r c e n t a t SO0C ., and
3 p e r c e n t a t 60°C,
F or a l l c a lc u l a ti o n s w ith d e te r g e n ts ,
H ss 7 .1 6 4 x IO -6 .
The KT v s . C c u rv e s (F ig u re 8) s t r i k i n g l y i l l u s t r a t e th e
change t h a t ta k e s p la c e i n soap s o lu tio n s a t th e c r i t i c a l con­
c e n tra tio n .
C o n d u c tiv ity and d e n s ity v s. c o n c e n tr a tio n c u rv e s
a ls o show a b ru p t changes a t th e c r i t i c a l c o n c e n tr a tio n .
In a l l
c a s e s , e x c e p t d o d ec y ltrim e th y la m m o n iw c h lo r id e , s c a t t e r i n g b e­
low th e c r i t i c a l c o n c e n tr a tio n s was I n s i g n i f i c a n t .
F or t h i s
d e te r g e n t, r e p r o d u c ib le s c a t t e r i n g below th e c r i t i c a l concen­
t r a t i o n o c c u rre d , a lth o u g h n o t shown i n F ig u re 8 .
This su g ­
g e s t s , more d r a m a tic a lly th a n i n th e c a se o f th e o th e r s u r f a c ­
t a n t s , t h a t m ic e lle s do e x i s t below th e c r i t i c a l c o n c e n tra tio n
in sm a ll num bers.
The abnorm al r i s e i n t h i s c a se co u ld be due
to a s l i g h t amount o f im p u rity w hich i s s o l u b i l i z e d i n th e mi­
c e lle .
I t sh o u ld be remembered, how ever, t h a t th e c r i t i c a l
c o n c e n tr a tio n i s n o t a p o in t, b u t a ra n g e .
A t y p i c a l T r s . C c u rv e , v i z . , f o r an uncharged polymer
37
h [ c - c .]
FOR
figure 6
PR
D
IR! ME BR +
TRI ME I o
BU 7
ET •
C in g / c c
figure
7
38
SCATTERING
ME A
TRI ME
TRI ME BR
TRI ME CL X
TRI H o
C in g / c c
figure 8
CURVES
FOR
39
s m a lle r th an o n e - tw e n tie th th e wave le n g th o f in c id e n t l i g h t .
I s s im ila r to t h a t f o r dodecyltrlm ethylaram oniiai brom ide and
c h lo r id e ex cep t t h a t i t goes th ro u g h th e o r i g i n .
The le v e lin g
o f f a t h ig h e r c o n c e n tr a tio n s i s due to th e o rd e rin g o f s o lu te
m o le c u le s, w hich r e s u l t s i n i n t e r f e r e n c e e f f e c t s .
The tu r b id ­
i t y v s . c o n c e n tr a tio n p l o t s b r in g o u t q u ite c l e a r l y which p o in ts
can be employed i n th e l e a s t sq u a re s method o f d e te rm in in g
c r i t i c a l c o n c e n tr a tio n and m o le c u la r w e ig h t.
a ls o c l e a r l y in d ic a t e d .
Any anom alies a r e
From F ig u re 8 th e d e s ir e d ran g e of
p o in ts to be used i n th e m o le c u la r w eig h t c a l c u l a t i o n s i s sug­
g e s te d , I t i s c l e a r t h a t n e a r th e c r i t i c a l c o n c e n tr a tio n s , th e
e r r o r i n a p a r t i c u l a r v a lu e o f nTn i s g r e a te r th a n a t h ig h e r
c o n c e n tr a tio n s .
H(C-C0 )
T
S in ce th e e q u a tio n used f o r c a lc u l a ti o n s h as an
term , p o in ts v ery c lo s e to th e c r i t i c a l c o n c e n tra tio n
sh o u ld be a v o id e d , and fu rth e rm o re , we would e x p e ct th e s e p o in ts
to show g r e a t e s t d i s piacem ent from th e l e a s t sq u a re s cu rv e f o r
H(C-C0 )
v s . C.
T
P erhaps a b e t t e r way of w e ig h tin g th e p o in ts f o r l e a s t
sq u a re s c a l c u l a t i o n would have been to use
fl=
H(C1-C0 ) - AT1 - SC1T1
At h ig h e r c o n c e n tr a tio n s , th e m ic e lle s may n o t a c t in d ep en d en tly
o f one a n o th e r and, t h e r e f o r e , assu m p tio n s made i n d e riv in g th e
l i g h t s c a t t e r i n g e q u a tio n would n o t h o ld .
I t l a d e s ir a b le th e n
40
to use in te r m e d ia te p o i n t s .
I n th e c a s e o f th e m eth y l, e th y l and d ie th y l s a l t s , th e
KT v s . C cu rv e d id n o t le v e l o f f b u t in s t e a d r o s e sh a rp ly a t
c o n c e n tr a tio n s ab o u t 0 .0 1 g /c c .
Only th o s e p o in ts below t h i s
c o n c e n tr a tio n were used in c a l c u l a t i n g m o le cu lar w e ig h ts.
The e t h y l, p ro p y l and b u ty l s a l t s were ru n a t 3 7 °, 50°,
and 65°C ., r e s p e c t i v e l y .
The o nly o th e r d e te r g e n t o b serv ed a t
a te m p e ra tu re g r e a t e r th a n 30°C. was tr im e th y l io d id e s a l t a t
45°C.
These h ig h e r te m p e ra tu re s were used b ec au se o f th e lim ­
i t e d s o l u b i l i t y o f th e d e te r g e n ts a t low er te m p e ra tu re s .
— v s . C p l o t s . F ig u re s 6 and 7 , r e p r e s e n t th e b e s t
s t r a i g h t l i n e s o b ta in a b le from th e ex p e rim e n ta l d a t a .
Table I I
g iv e s th e c a lc u l a te d r e s u l t s .
M olecu lar w eig h ts f o r d e te r g e n ts s tu d ie d by Anacker ( 3 ) ,
who r e p o r te d v a lu e s o f 12,300 and 15,500 f o r dodecylammonium
c h lo r id e and do decy Itrimethylammonixim brom ide r e s p e c tiv e ly , a r e
i n f a i r agreem ent w ith th e c o rre sp o n d in g v a lu e s o b ta in e d i n th is
s tu d y .
I n th e c a se o f th e dodecylalkylsmtmonium c h lo r id e s and
trim eth y lam m o n lm io d id e , s ta n d a r d is a tio n o f th e r e s u l t s to
30®C. was d o ie by c a l c u l a t i n g th e r a t e of change o f m o le cu lar
w eight w ith te m p e ra tu re f o r dodecyltrim othylam m onlurn brom ide
u s in g A nacker’ s d a ta , assum ing th e same r a t e h e ld f o r th e s e ma­
te ria ls .
These ap p ro x im a tio n s a r e ro u g h .
Time d id n o t p erm it
an in d iv id u a l stu d y o f th e s e s a l t s w ith te m p e ra tu re change.
41
TABLE I I
C a lc u la te d R e s u lts
S lope
Ce ( g /o e e) x IO5
DEPEROENT
11.69
M olecular
W eight*
DedecylmethylajRBioniu* c h lo r id e
,00314
Dedecylethylammonlum c h lo r id e
,00304
71,900
D odecylprepylaem onlum c h lo r id e
.00301
36,000
Dodecylbutylam m onlurn o h le r ld e
,00279
28,900
D odecyldlethylam m onlm c h lo r id e
.00336
5 .9 6
52,300
Dodecyltrlh y d ro g en am m . c h lo r id e
,00290
13.13
14, 400
DodecyltrimethylamBie c h lo r id e
.00544
8.31
9,300
D odecyltrim ethylaw m onitai brom ide
.00453
1 0 .6 2
17,200
D odecyltrim ethylam m onlm io d id e
.00347
Dedecylethylsunae C h lo re
a t 38°Ce
.00309
6 .2 2
65,900
Dodeoylp ro p y Isuame C h lo re a t 48°Ce
.00346
1 6 .7 3
31,900
DodecylbUtylajame C h lo re
a t 65°Ce
.00440
5 ,6 3
28,300
D odecyltrim ethylam m e i o d . a t 460C#
.00382
1 0 .6 0
49,400
*At SO0Ce u n le s s o th e rw ise s p e c i f i e d .
74,600
58,700
42
V II. DISCUSSION
A lthough no m easurem ents were a tte m p te d , dissym m etry and
d e p o la r iz a tio n o f th e s c a t t e r e d l i g h t have been assumed to be
n e g lig ib le .
The r e l a t i v e l y sm a ll v a lu e s o f th e m o le cu lar
w e ig h ts su p p o rt th e assu m p tio n .
A ccording to th e ex p e rim en ta l r e s u l t s , m ic e lle w eig h ts a r e
s tr o n g ly dependent upon th e make-up o f th e s u b s t i t u e n t groups
p r e s e n t on th e n itr o g e n .
The a u th o r a t t h i s tim e I s unable to
p r e s e n t a com plete and f u l l y c o n s is te n t e x p la n a tio n of th e ob­
se rv e d phenomena.
The fo llo w in g c o n s id e r a tio n s may be o f some
H a l t e d v a lu e .
The e q u ilib riu m s i z e o f th e m ic e lle l a d eterm in ed by th e
i n t e r p l a y o f two f o r c e s .
The s h o r t ran g e van d e r Waal *s f o r c e s
h o ld th e lo n g hy d ro carb o n t a i l s of th e s u r f a c ta n t Io n s to g e th e r
i n th e m ic e l le .
S ierg y i s r e le a s e d when a number o f h y d ro -c a r­
bon t a i l s a r e removed from th e su rro u n d in g w a te r and b ro u g h t
I n to c o n ta c t w ith each o th e r in th e m ic e lle .
The energy given
up l s ro u g h ly p r o p o r tio n a l to th e number of Io n a w hich a g g re ­
g a te .
On th e o th e r hand, lo n g ran g e coulom bic f o r c e s must be
overcome when ch arg ed ends o f th e h y drocarbon c h a in s a re b ro u g h t
to g e th e r In th e o u te r s u r fa c e of th e m ic e lle .
q u ir e s th e e x p e n d itu re of e n e rg y .
T h is p ro c e ss r e ­
Tlie la r g e r th e m ic e lle th e
g r e a t e r w i l l be th e e l e c t r i c a l work r e q u ir e d to b r in g an a d d i­
t i o n a l lo n g -c h a in io n i n t o th e m ic e lle .
When th e I n i t i a l c h a in s come to g e th e r , th e energy r e le a s e d
45
i s g r e a t e r th a n th e energy r e q u ir e d to b rin g th e p o la r heads
to g e th e r .
S in ce th e energy r e le a s e d i s n e g a tiv e by co n v e n tio n ,
th e t o t a l energy o f th e m ic e lle , i . e , , th e a lg e b r a ic a m of th e
energy g a in e d by b r in g in g K hydrocarbon t a i l s to g e th e r and th e
e l e c t r i c a l work which must be done, w i l l re a c h a minimum v a lu e
w hich I s n e g a tiv e .
At t h i s minimum, th e v a lu e o f th e correspond­
in g N r e p r e s e n ts th e number of m o le cu les making up th e m ic e lle
• f m ast s t a b l e c o n f ig u r a tio n .
At t h i s p o in t dW/dH = 0 , in
w hich W i s eq u al to th e t o t a l energy o f th e m ic e l le .
Any f a c t o r w hich w i l l m odify th e f o r c e s in v o lv e d w ill a f ­
f e c t th e e q u ilib riu m s i z e of th e m ic e lle .
The a d s o rp tio n on, or
c lo s e appro ach to , th e s u r fa c e o f th e m ic e lle of o p p o s ite ly
c h a rg e d gegen Io n s w i l l sc re e n th e a c tio n o f th e ch arg es on th e
m ic e lle and w i l l red u ce th e e l e c t r i c a l work r e q u ir e d to b r in g
a d d itio n a l lo n g -c h a in Io n s i n t o th e a g g re g a te .
Hence in th e
p re se n c e of added e l e c t r o l y t e , th e e q u ilib riu m s i z e of th e mi­
c e l l e w i l l be la r g e r th a n when no a d d i tio n a l e l e c t r o l y t e i s
p r e s e n t.
Any f a c t o r w hich w ill I n c r e a s e th e d is ta n c e between th e n i ­
tro g e n atoms i n th e s u r f a c e o f th e m ic e lle w i l l d e c re a se th e
s u r f a c e c h a rg e d e n s ity and sh o u ld a ls o d e c re a se th e e l e c t r i c a l
work n e c e s s a ry to b r in g a new m o lecu le I n to th e m ic e l le .
th e s iz e o f th e m ic e lle sh o u ld i n c r e a s e .
Thus
However, s e p a r a tio n
o f th e p o la r h ead s w i l l r e s u l t i n some s e p a r a tio n o f th e h ydro­
carbon t a i l s , w hich i n tu r n would te n d to d e c re a s e th e m ic e lle
44
siz e *
These two e f f e c t s th e n p a r t i a l l y c a n c e l each o th e r*
us examine
L et
th e fo llo w in g t a b l e w ith th e above c o n s id e r a tio n s
i n m ind.
C o n s id e r
dodecylaBimoniuia c h lo r id e as a member- of each of
th e th r e e h o r iz o n ta l row s.
I n th e to p row we n o tic e a marked
I n c r e a s e I n th e a g g re g a tio n number when one of th e hydrogen a t ­
oms on th e n itro g e n i s r e p la c e d by an a lk y l r a d i c a l .
S in ce th e
n itr o g e n atom I s s m a lle r th an a carb o n atom , and bonds to tr a h e d r a l l y — o r ap p ro x im a tely o o - -to f o u r o th e r atoms o r g ro u p s, i t
i s u n lik e ly t h a t th e n itr o g e n atoms I n a d ja c e n t c h a in s a re
f o r c e d a p a r t by th e replacem ent*
Hence th e s i z e in c r e a s e can ­
n o t be due to a r e d u c tio n i n th e e l e c t r i c a l work r e q u ir e d to
form a m ic e lle from in d e p en d en t Iona*
Tine a lk y l r a d i c a l , i f i t
does a n y th in g , f o r c e s th e c o u n te r io n away from th e n itr o g e n
atom and th u s sh o u ld te n d to make th e a g g re g a tio n number f a l l
I n s te a d of r is e *
T his may be th e e x p la n a tio n f o r th e observed
d e c re a se from th e second member on*
The re a s o n f o r th e b ig
d if f e r e n c e i n a g g re g a tio n number betw een do dec y lazmonium c h lo ­
r i d e and dodecylm ethylam m onlurn c h lo r id e i s n e t ev id en t*
In th e second h o r i z o n ta l row th e r e i s an in c r e a s e i n mi­
c e l l a r w eig h t as we go from l e f t to r ig h t*
A p o s s ib le ex p lan a­
t i o n of t h i s in c r e a s e i s th e f o r c in g a p a r t of n itr o g e n atoms in
a d ja c e n t h e a d s.
I n th e bottom h o r iz o n ta l row we m ight e x p la in an in c r e a s e
i n m ic e lle s i z e as we go from dodecylammonitan c h lo r id e to do-
45
d eo y ltrim eth y laim aen lu e c h lo r id e a g a in as In v o lv in g an I n c r e a s e
In th e d is ta n c e betw een a d ja c e n t n itr o g e n ato m s.
The n itr o g e n
atoms f o r th e tr im e th y l m ic e lle a r e f a r t h e r a p a r t th a n f o r any
o th e r and, i f th e d is ta n c e betw een n itr o g e n atoms were th e o n ly
f a c t o r to be c o n s id e re d , we would ex p ect t h i s m ic e lle to be th e
l a r g e s t o f any c o n s id e r e d .
An I n c r e a s e d d is ta n c e o f c l o s e s t
approach o f th e gegen io n to th e n itr o g e n atom and some s e p a r a ­
t i o n of th e h y d ro carb o n t a i l s may be th e p rim ary f a c t o r s d e t e r ­
m ining th e sm all s i z e .
TABLE I I I
Com parison Between S u r f a c ta n ts a t 30°C.
T rihydrogen
M ethyl
MW= 14,400
N= 65
MW= 74,600
N = 317
T rihydrogen
MW= 14,400
N = 65
T rihydrogen
MW = 14, 400
N = 65
E thyl
MW:= 7 1 ,9 0 0
N= 288
Propyl
B utyl
MW= 3 6 ,0 0 0 MW= 2 8 ,900
N= 137
N= 96
m e th y l
MW= 52,300
N = 188
T rlm eth y l
MW = 9,3 0 0
N= 35
The o b serv ed f a l l o f a g g re g a tio n number a s we descend th e
t h i r d v e r t i c a l column, assum ing tr im e th y l and t r i e th y l to b e ap­
p ro x im a te ly th e same s i z e , would le a d us to co n clu d e t h a t in
46
t h i s s e r i e s , p r o g r e s s iv e f o r c in g b ack o f th e gegen Io n from th e
n itr o g e n atom was th e c o n t r o ll in g f a c to r #
This may a ls o be th e
c a se i n th e second v e r t i c a l column#
A nother f a c t o r w hich sh o u ld be c o n s id e re d i s th e " e f f e c ­
t i v e " d i e l e c t r i c c o n s ta n t i n th e r e g io n o f th e c h a rg e on th e
n itr o g e n atom#
S in ce ooulom bic r e p u ls io n betw een l i k e c h a rg e s
v a r ie s in v e r s e ly as th e d i e l e c t r i c c o n s ta n t su rro u n d in g th e
c h a rg e s , we would ex p e ct two ch a rg e d monomer h ead s to r e p e l
each o th e r w ith much g r e a t e r f o r c e where a lk y l groups su rro u n d
th e n itr o g e n atom th a n where th e y do n o t.
We w ould th e r e f o r e
expect m ic e lle s i z e to d e c re a s e as th e number o f a lk y l groups
around th e n itr o g e n atom In c re a s e s #
In d e e d , th e r e s u l t s show
t h a t th e m o le c u la r w eig h t of th e m ic e lle d e c re a s e s in th e s e ­
r ie s a lk y l-* -d ia lk y l- * - tr ia lk y l.
A lso , as th e a l i p h a t i c c h a in
i s le n g th e n e d th e m o le c u la r w eig h t d ec re ase s#
T h is e f f e c t i s
m ost pronounced i n th e c a se o f t r i a l k y l s a l t s , and, to g e th e r
w ith gegen Io n h in d ra n c e , e x p la in s th e low v a lu e o f t h e i r mi­
c e lle s iz e .
A nother e f f e c t w orth m e n tio n in g , b u t o f l e s s e r im p o rta n ce,
i s th e van d er Waal a t t r a c t i o n betw een a lk y l groups around a
n itr o g e n atom and a lk y l groups of an a d ja c e n t monomer h ead .
T his would c a u se a sm all n e g a tiv e c o n tr ib u tio n t o th e t o t a l en­
ergy o f th e system and te n d to in c r e a s e m o le cu lar w e ig h t.
An I n t e r e s t i n g com parison can b e made betw een th e t r l hy­
drogen and t r i a l k y l s a l t s where gegen io n and a lk y l group M n -
47
d ran ce s a r e a t a minimum and maximum r e s p e c t i v e l y .
S in ce t h e i r
m o le c u la r w e ig h ts a r e o f n e a r ly th e same o rd e r o f m ag n itu d e, i t
can be deduced t h a t th e two s t e r i c e f f e c t s a r e o f n e a r ly th e
same o rd e r o f m ag n itu d e.
F u rth e rm o re , when an a lk y l group i s
removed from th e t r i a l k y l o r added t o th e trih y d ro g e n s a l t to
g iv e d ia lk y l and a lk y l s a l t s r e s p e c t i v e l y : i n th e f i r s t i n ­
s ta n c e th e gegen io n e f f e c t i s enhanced w h ile th e a lk y l h in ­
d ran ce e f f e c t changes l i t t l e ; i n th e c a s e o f th e trih y d ro g e n
and e th y l, th e g r e a t e r change i s i n th e a lk y l h in d ra n c e .
In
b o th c a s e s one e f f e c t i s enhanced and m ic e lle s o f much l a r g e r
m o le c u la r w eig h t can be e x p e c te d .
This i s e v id e n t i n T able I I I ,
where t rim e th y I , MW=L 9 , 3 0 0 d i e t h y l , MW= 5 2 ,3 0 0 ; and t r i hy­
d rogen, MW-=• 14, 4 0 0 e t h y l , MWsm 7 1 ,9 0 0 .
The l a r g e jump in
m o le c u la r w eig h t o b se rv e d from dodecylammonlua c h lo r id e to dod e o y la lk y lammonium c h lo r id e may be due to a d e c re a s e i n th e
" e f f e c t i v e d i e l e c t r i c c o n s ta n t."
T his would mean t h a t in th e
c a s e o f t r l hydro g en , a lth o u g h th e gegen io n can approach c lo s e ­
l y , th e e f f e c t i v e d i e l e c t r i c c o n s ta n t su rro u n d in g th e n itr o g e n
atom would be g r e a t e r th an i n th e c a s e o f e t h y l, o r even d ie th ­
y l ; and so s h ie ld in g by th e gegen io n would be g r e a t e r in c a s e s
where a lk y l groups su rro u n d th e n itr o g e n atom .
No a tte m p t was made to d e te rm in e th e shape o f th e m ic e lle s ,
b u t i t i s e v id e n t from sim p le c a l c u l a t i o n t h a t th e m ic e lle s a r e
p ro b a b ly n o t s p h e r ic a l under th e c o n d itio n s o f t h i s s tu d y .
A
s p h e r ic a l m ic e lle would have a d ia m e te r no g r e a t e r th a n tw ic e
48
th e le n g th o f th e d o decyl c h a in , o r
2x 1 .2 6 x 10”8 x 12 cm.
I t s volume would b e 4 /3 TT (2 x 1 .2 6
x IO**8 x 12)® cm3 .
Assum­
in g a d e n s ity o f u n ity (more l i k e l y n e a r 0 .8 ) , th e m o le c u la r
w eight would be I x 4 /3 TT(2 x 1 .2 6
x ICT8 x 1 2 )5 x 6 x IO23,
or about 8 ,7 0 0 .
I s th e o n ly s u r f a c ta n t r e ­
The tr lm e th y l s a l t
p o r te d h e re whose m o le c u la r w eig h t I s I n t h i s ra n g e .
In th e above d is c u s s io n m o le c u la r w eig h t I s c o r r e la te d
w ith m ic e lle s t r u c t u r e .
A c o r r e l a t i o n co u ld be made of m ic e lle
s t r u c t u r e and c r i t i c a l c o n c e n tr a tio n .
Perhaps f u t u r e knowledge
o f c r i t i c a l c o n c e n tr a tio n and m o le c u la r w eight r e l a t i o n s h i p
w i l l I llu m in a te m ic e lle s t r u c t u r e .
T able I I I shows t h a t a d i r e c t I n c r e a s e In c r i t i c a l concen­
t r a t i o n o cc u rs i n d o d e c y ltrlmethylammonlum h a l id e s w ith p ro ­
g r e s s io n from I o d id e to c h lo r id e a n io n s .
One m ight ex p ect t h a t
th e n e u t r a l i z i n g e f f e c t of th e gegen Io n depends on th e d i s s ta n c e o f ap p ro ach o f th e monomer head and th e gegen Io n .
I s a p p a re n tly a f u n c tio n of th e s i z e o f th e io n .
T h is
However, th e
nS lz e n o f th e Io n In c lu d e s th e I o n ic r a d iu s p lu s th e ad so rb ed
w a te r.
From h e a t of s o lu tio n d a t a , and as a consequence o f th e
Debye-Huckel th e o ry , th e c h lo r id e io n i s h y d ra te d th e most and
th e io d id e Io n th e l e a s t .
H y d ra tio n would te n d to sc re e n th e
I o n ic f i e l d by alig n m en t o f th e w a te r mo eo u les a lo n g th e l i n e s
o f f o r c e , th e re b y in c r e a s in g th e d i e l e c t r i c c o n s ta n t.
Accord­
in g to io n ic co n d u ctan ce d a ta , a t i n f i n i t e d i l u t i o n th e r e l a ­
t i v e s i z e o f th e io n s I n s o lu tio n can be o b ta in e d , showing th e
49
brom ide Ie n to be s l i g h t l y la r g e r th a n th e I o d id e and c h lo r id e
Io n s , e h ic h a r e ab o u t th e same s i z e .
In view o f t h i s , th e ex­
p e rim e n ta l r e s u l t s r e p o r te d h e re a r e s u r p r i s in g , and t h e i r I n ­
t e r p r e t a t i o n Im poses a fo rm id a b le c h a lle n g e .
60
V I I I . BRIEF
SUMMARY
R e la te d d e te r g e n ts w ere p re p a re d by m o d ific a tio n of s ta n d ­
a rd m ethods, and a r e l a t i v e l y sim p le and r a p id method f o r h a lo ­
gen a n a ly s is was d e v is e d .
The l i g h t s c a t t e r i n g in s tru m e n t was s ta n d a r d iz e d w ith su ­
c r o s e and r a f f a n o a e w ith f a i r ag reem en t.
C r i t i c a l c o n c e n tr a tio n s and m o le c u la r w eig h ts of m ic e lle s
w ere d eterm in ed f o r n in e d e te r g e n ts .
Rough t h e o r e t i c a l c o r r e ­
l a t i o n was a tte m p te d i n s t r i c t l y q u a l i t a t i v e te rm s .
There was
c o n s id e r a b le s p e c u la tio n co n c e rn in g th e r e l a t i o n betw een m olec­
u l a r w eigh t and m ic e lle s t r u c t u r e .
F a c to rs te n d in g to I n c r e a s e
m o le c u la r w eig h t w ere th o u g h t to b e :
a , c lo s e n e s s o f approach o f th e gegen io n to th e monomer
h ead ,
b , in c r e a s e d s e p a r a tio n o f p o la r h eads by th e in tr o d u c ­
t i o n o f groups around th e n itr o g e n atom,
c , some van d er Waal a t t r a c t i o n betw een a lk y l groups of
a d ja c e n t m o le c u le s.
F a c to rs te n d in g to d e c re a s e m o le c u la r w eig h t were th o u g h t to b e;
a . h in d ra n c e of th e gegen io n ,
b . c lo s e ap p ro ach of th e c h a rg e d monomer h e a d s,
c . in c r e a s e i n a lk y l groups around th e n itr o g e n atom,
th e re b y lo w e rin g th e " e f f e c t i v e " d i e l e c t r i c c o n s ta n t
su rro u n d in g th e c h a rg e ,
d . s e p a r a tio n o f th e h y d ro carb o n t a i l s due to b u lk in e s s
51
o f a lk y l groups around th e n itr o g e n atom .
The I n flu e n c e o f th e gegen Io n on th e e q u ll i b r i m
th e m ic e lle was c l e a r l y dem onstret e d .
s iz e o f
The e f f e c t o f th e io d id e
io n compared to th e brom ide and c h lo r id e io n s ap p e ared to be
o u t o f p r o p o rtio n i n view o f th e r e l a t i v e s i z e o f th e h y d ra te d
Io n s e s tim a te d from c o n d u c tiv ity d a t a .
However, th e s iz e o f
th e m ic e lle d id n o t seem to v ary a s th e s i z e o f th e io n .
The
s i z e o f th e m ic e lle d id v ary I n v e r s e ly as th e d eg ree of h y d ra­
t i o n o f th e io n , b u t t h i s may b e f o r t u i t o u s .
52
IX .
A Q K N 0W LEI3G ZM S3TS
The a u th o r w ish es to thank Dr. 5. W# A nacker f o r M a I n ­
s p i r a t i o n and encouragem ent.
A p p re c ia tio n l a a ls o extended to
th e o th e r members of th e d ep a rtm en t, e s p e c ia lly Dr. B inder and
Dr. Leon Johnson, f o r t h e i r c o o p e ra tio n .
The a u th o r a p p r e c ia te s th e g ra n t made a v a ila b le by th e
R esearch C o rp o ra tio n o f Hew York.
53
X . LITERATURE CITED
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4 . B ender, J . Chao. E d., 29, 15 (1 9 5 2 ).
5 . Debye, P ., Ann. N• Y, Acad. S c l . , 51, 575 (1 9 4 9 ).
6 . Debye and A nacker, J . Phys. &C o llo id Chem.,
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1 9 . MoB ain, " F r o n tie r s i n C o llo id C h e m istry ," V ol. V III, I n t e r s c ie n c e P u b lis h e rs (1 9 6 0 ).
2 0 . McBain , T ra n s. F arad ay S o c ., 9 , 99 (1 9 1 3 ).
2 1 . McCartney e t a l . , J . Chem. P h y s., 14, 687 (1 9 4 6 ).
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