Di-Stimuli Responsive Diblock and
Triblock Copolymer Particles
Nancy Weber, John Texter *, and Klaus Tauer
Max Planck Institute for Colloids and Interfaces
Department of Colloid Chemistry
14476 Golm, Germany
* during sabbatical leave from
Eastern Michigan University
Ypsilanti, MI 48197, USA
1
What‘s Coming:
block copolymer & particle synthesis
not so common characterization technique:
Ultrasonic Resonator Technology (URT)
results for different PNIPAM block copolymers
(such as PNIPAM, P1-PNIPAM, P1-PNIPAM-P2, PIL-PNIPAM, PIL-PNIPAM-PMMA)
methods: URT, DLS, salt addition, FT-IR spectroscopy
2
bockcopolymer particles synthesis
Ce4+
NIPAM
OH
OH
aggregation of
PNIPAM blocks
(T>32°C)
hydrophilic polymer
reactive particles
(intermediates)
RT
T > 32 °C
PSS - PNIPAM
PNIPAM is hydrophobic at T > LCST, but
contains still ca. 45 vol-% water and hence,
it is quite a unique reaction space
sequental addition of monomers
allows the synthesis of
multi block copolymers and very
special latex particles
4
Newton – Laplace equation
1
U
 
 - compressibility
 - density
5
cell 1: water
cell 2: sample
DU = U2 – U1
H2O
sample
sample volume: 200 µl
6
T < LCST
sound wave
not to scale
diluted and more or less
homogeneous solution
7
aggregation at T > LCST
water is released and overall compressibility increases and hence,
speed of sound decreases
H2O
H2O
sound wave
H2O
not to scale
H2O
we are tracking hydration changes:
the adhering layer of water molecules
8
URT data evaluation sequence
PSS – PNIPAM block copolymer
heating
1540
1530
0,0
sample
d U/dT (m/(s °C))
1510
1500
1490
H2O
1480
1470
15
20
25
30
35
40
45
T (°C)
-0,1
-0,2
-0,3
-0,4
-0,5
15
4,5
20
25
30
35
40
45
T (°C)
4,0
U (m/s)
U (m/s)
1520
3,5
3,0
LCST
2,5
2,0
15
20
25
30
35
40
45
T (°C)
DU = Usample – Uwater
9
0.0
d U/dT (m/(s °C))
-0.2
-0.4
-0.6
double hydrophilic block copolymers
(almost) no influence on LCST of PNIPAM
-0.8
-1.0
15
PNIPAM
PEG-PNIPAM
PSS-PNIPAM
PDADMAC-PNIPAM
20
25
30
35
40
45
T (°C)
10
heating – cooling hysteresis
34,0
33,5
T (°C)
PEG-PNIPAM
33,0
PDADMAC-PNIPAM
PSS-PNIPAM
PNIPAM
32,5
PNIPAM
PSS-PNIPAM
PDADMAC-PNIPAM
32,0
PEG-PNIPAM
31,5
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
c (wt-%)
300 mK / min (standard conditions)
11
concentration dependence of DLS data
105
Di (nm)
PNIPAM
104
PEG-PNIPAM
103
PDADMAC-PNIPAM
PSS-PNIPAM
102
T = 35 °C
101
0,01
0,1
1
c (wt-%)
12
d U/dT (m/(s °C))
hydrophilic - hydrophobic attachments to PNIPAM
0,0
PEG(5k) - PNIPAM orig
-0,5
PNIPAM 1%
-1,0
PEG(5k) - PNIPAM - PS latex
-1,5
-2,0
-2,5
15
20
25
30
T (°C)
35
40
45
increasing
hydrophobicity
13
influence of the PEG chain length
PEG - PNIPAM
PEG - PNIPAM - PS
-0,1
d U/dT (m/(s °C))
d U/dT (m/(s °C))
0,0
-0,2
-0,3
-0,4
-0,5
-0,6
20 25 30 35 40 45 50 55
0,0
-0,5
-1,0
-1,5
-2,0
-2,5
15 20 25 30 35 40 45 50
T (°C)
T (°C)
PEG 5.000 g/mol
PEG 106 g/mol
14
a case study
two block copolymers
PIL - PNIPAM
hydrophobic effect of alkyl chains ?
PDADMAC - PNIPAM
PEL behavior (double hydrophilic polymer)
poly(1 - (11 - acryloyloxyundecyl) – 3 – methylimidazolium bromide (PIL)
d U/dT (m/(s °C))
0,1
sulfonated
PS latex sulfoniert
0,0
PDADMAC-PNIPAM
-0,1
-0,2
PIL - PNIPAM
-0,3
-0,4
-0,5
0
10
20
30
40
50
60
T (°C)
16
3500
3000
Di (nm)
2500
2000
PIL - PNIPAM
1500
1000
PDADMAC - PNIPAM
500
PS latex sulfonated
0
0
10
20
30
40
50
60
70
T (°C)
URT and DLS reveal
clear difference between PIL – PNIPAM and PDADMAC - PNIPAM
17
Heating cooling cycle (PIL – PNIPAM)
a initial condensation as solution warms;
b the whole solution has warmed;
c the suspension is actively boiling;
d the suspension is being cooled in ice;
e clear solution after re-dissolution of
poly(NIPAM) cores following cooling in (d).
PIL - PNIPAM
increasing ionic strength
(KBr, NaBF4 addition)
changing the solution state
19
KBr addition/removal cycle
a starting 1.9% (w/w) solution of PIL
b just noticeable turbidity at abut 0.4 M KBr and “hard foam” due to
diblock
becoming essentially a nonionic surfactant due to high bormide
binding;
c highly turbid condensation product at 2.56 M KBr;
d same as in (c) but in smaller culture tube;
e after extensive dialysis (18 h) to remove excess KBr
KBr addition
temperature
KBr
104
PIL - PNIPAM / 23°C
Di (nm)
103
102
101
PIL - PNIPAM
NaBF4
KBr
100
0,0 0,5 1,0 1,5 2,0
CKBr (M)
particles size evolution of poly(ILBr-b-NIPAM)
solution upon stepwise addition of 4.64 M
aqueous KBr solution
0
20
40
60
T (°C)
rather unexpected result
(PNIPAM is turned off)
also no URT response
21
PNIPAM behaves differently in PIL copolymers
than in other block copolymers
with PDADMAC, PSS, or PEG
?
22
complex formation between PIL and PNIPAM
PIL + PNIPAM: components and physical mixture
0,02
104
-0,02
Di (nm)
d U (m/(s °C))
0,00
-0,04
-0,06
103
-0,08
102
-0,10
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70
T (°C)
PIL-2
T (°C)
PNIPAM
PNIPAM+PIL-2
physical mixture of 1:1 by weight
23
PIL + PNIPAM: physical mixture equal masses
-0,02
d U (m/(s °C))
-0,04
-0,05
103
Di (nm)
104
-0,03
-0,06
-0,07
-0,08
0
10
20
30
40
50
60
102
70
T (°C)
formation of a complex between
PIL and PNIPAM
physical mixture of 1:1 by weight
24
0,00
nNIPAM
Rn 
nIL
Rn=0.125
Rn=1
d U (m/(s °C)
-0,02
Rn=7
-0,04
Rn=13
-0,06
c = 0.4 wt-%
-0,08
0
10
20
30
40
50
60
T (°C)
all mixtures are solutions (no visible turbidity)
25
complex formation between PNIPAM and PIL
monomers and polymers
Br
O
O
C H2
C H2
C H2
C H2
C H2
C H2
C H2
N
C H2
C H2
C H2
N
C H2
C H2 C H
C O
C H3
transmission
transmission
NH
C
H
C H3
PIL 1
PNIPAM+PIL1
(2)
(1)
1300 1400 1500 1600 1700 1800
wavenumber (cm-1)
amide band
PNIPAM b
1300 1350 1400 1300 1350 1400
PIL- PNIPAM (NW23A)
wavenumber (cm-1)
imidazolium ring
26
blockcopolymer particles synthesis
due to complex formation: change of properties of the reactive intermediate
if hydrophilic precursor polymer is replaced by PIL
ionic-like interior causes
difficulties to incorporate
nonpolar or hydrophobic
monomers
styrene almost no polymerization
MMA performs a little better
PIL – PNIPAM – precursor copolymers
-0.15
-0.20
-0.4
103
-0.6
102
PNIPAM
101
0
10
20
30
40
T (°C)
50
60
-0.8
-0.25
-0.30
102
-0.35
-1.0
70
d U/dT (m/s°C))
-0.2
103
Di (nm)
Di (nm)
104
d U/dT (m/(s°C))
0.0
-0.40
PIL - PNIPAM (NW18A)
PIL - PNIPAM (NW23A)
101
0
10
20
30
40
50
60
-0.45
70
T (°C)
28
PIL – PNIPAM – PMMA triblock copolymers
-0.2
-0.3
precursor diblocks
-0.3
-0.4
-0.5
-0.5
Di (nm)
d U/dT (m/(s °C))
-0.4
-0.6
-0.6
102
-0.7
-0.7
-0.8
PIL - PNIPAM - PMMA (NW18B)
PIL - PNIPAM - PMMA (NW18B)
PIL - PNIPAM - PMMA (NW23B)
PIL - PNIPAM - PMMA (NW23B)
101
-0.9
0
10
20
30
T (°C)
40
50
60
0
10
20
30
40
50
60
-0.8
70
T (°C)
29
d U/dT (m/(s°C))
103
explanation
during cooling: the solubility of the
PNIPAM block increases and pulls the
presumably quite short PMMA into the
water
during heating: the whole precipitation
occurs stepwise:
1. PMMA block causes aggregation as
recorded by DLS at lower temperature
2. at higher temperature the hydration
water is released as recorded by URT
30
Nancy Weber
John Texter
Summary
PIL – PNIPAM diblock copolymers show responsiveness
against temperature and salt
PIL – PNIPAM – PMMA triblock copolymers show a
transition temperature below room temperature
URT is a powerful tool to study phase transitions and a
complementary method to established techniques
complex formation between imidazolium compounds
and NIPAM determines the scene
Thank You
32