Makromol. Chem. 185,2337--2346
(1984)
2337
Anionic polymerization of
exo-3,4,5-trithiatetracyclo[5.5.1 .0296.08912]tridec-10-ene
(dicyclopentadiene trisulfide)
Teresa Baran, Andnej Duda, Stanistaw Penczek *
Polish Academy of Sciences, Centre of Molecular and Macromolecular Studies,
90-362 Lodi, Boczna 5, Poland
(Date of receipt: March 12, 1984)
SUMMARY:
(1)in
The anionic polymerization of exo-3,4,5-trithiatetracycl0[5.5.1.@,6.08*12]tride~-10-ene
bulk and/or in aromatic solvents (benzene, toluene) was studied. The polymerization was
initiated with sodium benzenethiolate (sodium cation complexed with dibenzo-18-crown-6).
Polymers with high-molecular weights were obtained (M, = I@, osmometrically). The polymerization was found to be living and reversible; the equilibrium monomer concentration
increases with the temperature. The ceiling temperature was estimated as 167 "C. The thermodynamic data of the polymerization in toluene was determined and compared with those of the
polymerization of ex0-3,4,5-trithiatricycl0[5.2.@~~]decane. The standard enthalpy AH'), =
-(6,6 f 0,6) kJ mol I and entropy AS: = - (29,3 +. 2,l) J .mol .K I of the polymerization of 1 were evaluated from the temperature dependence of the equilibrium monomer concentration, determined dilatometrically.
Introduction
Commercially available polymers of alkylene-polysulfides are produced mainly by
polycondensation of dichloroalkanes with alkalimetal polysulfides I).
The new possibilities in this field rest on the anionic copolymerization of elemental
sulfur (S,) with thiiranes2 ,).
S,
+ H2C-C
\/
S
/R'
R
'z
R' = R2 = H or CH3
R' = H, R2 = CH,
XO : Anionic initiator
Previously we have shown2 6, that, S, copolymerizes readily with unsubstituted
thiirane, 2-methylthiirane, and 2,2-dimethylthiirane, giving high-molecular copolymers A containing up to 85 wt.-Yo of sulfur. Sulfur in these products is chemically
bonded indeed, and the copolymers have the structure of linear alkylene polysulfides.
This was proved by means of 'HNMR, I3C NMR, and Raman spectroscopy2 @.
0025-1 16X/84/$03.00
2338
T. Baran, A. Duda, S. Penczek
Kinetics5 , 6, and thermodynamics6*') of S, copolymerization were also studied.
In the copolymerization of S, with thiiranes the low-molecular weight cyclic
oligomers $CH,-CR'R* j-S,A,n = 3,4, 5 ) are formed in addition to the high-molecular weight apparently linear p ~ l y m e r ~ .These
~ ) . oligomers are both intermediates
and by-products in the copolymerization process:
R' R'
\/
.--CH2C-Sle
R'
R'
=
=
R' R2
\/
R' R2
\/
. . .-CH2-C-S~xCH2-C-S,e
+
R2 = H or CH,
H, Rz = CH,
Thus, we studied separately the homopolymerization of cyclic polysulfides, using
orfho-fused 1,2,3-trithiolane derivatives of both norbornene and dicyclopentadiene6v9.lo) as model compounds.
Such fused 1,2,3-trithiolane systems can be obtained from elemental sulfur and the
corresponding olefine II
"Activator"
a>
S
(3)
1
NH,, amines, or 2,5-bis(octyldithio)-1,3,4-thiadiazoleare used as sulfur "activators".
The combination of these two processes, described above, opens a new way in the
synthesis of poly(alky1ene polysulfides) starting from elemental sulfur.
Anionic polymerization of exo-3,4,5-trithiatetracyclo[S.S.l.d*6.08,'2]tridec-10-ene.
..
2339
Emsley et al.14)studied the thermal homopolymerization of 1,2,3-trithiolanes, and
the copolymerization of these monomers with S, has also been reported 15). High
temperature polymerization led to low molecular weight products.
The present paper reports on the anionic polymerization of exo-3,4,5-trithiatetracyclo[5.5.1 .@*6.08,'2]tridec-10-ene (1) (dicyclopentadiene trisulfide) to the high-molecular weight polymer
= 105) and the thermodynamic data of this process.
(m,
Results and discussion
Polymerization conditions
The polymerization of the cyclic trisulfide 1, prepared from endo-dicyclopentadiene, was initiated with sodium benezenethiolate (sodium cation being complexed
with dibenzo-18-crown-6) and was carried out in bulk or in typical aromatic solvents
(toluene, benzene) at temperatures from 25 to 90"C. The resulting product is a glassy,
high-molecular weight polymer, soluble in benzene, toluene and in chloroform.
The elemental analyses of both monomer and polymer indicate that no elemental
sulfur is formed, i.e. the polymer has the same sulfur content as the monomer.
The analysis of the Raman spectra lead to the same conclusion (c.f. next section).
The equilibrium concentration of poly(1) depends both on the initial concentration of
monomer and on the temperature. As it could be shown dilatometrically (c.f. Exptl.
part) the change of the polymer concentration with the temperature is reversible.
Tab. 1 makes a comparison of molecular weights of poly(l), measured osmometrically (M, (osm.)) with those calculated with the assumption that each molecule of
initiator gives one macromolecule
(calc.)). The values are not very different, but
show some scatter if the process is treated as a living one. The reversible nature of the
polymerization manifested by the reversible changes of monomer and polymer concentrations with the temperature, and the data given in Tab. 1, indicate that the polymerization of 1is indeed close to a living process.
(m,
Microstructure of poly(1)
'H NMR spectra
The 'H NMR spectrum of monomer 1(Fig. 1 (a)) [d = 5,42 (2H; olefinic CH), 3,65
(2H, trithiolane ring CH), and 3,2 - 1,O (8H; complex region-cyclopentene CH,,
T. Baran, A. Duda, S. Penczek
2340
Tab. 1. Dependence of
[Ib
anof poly(1) on the polymerization parameters at 25 "C
mol-1.10-2
[I],
mole1
1,42
130
2,58
0,83
0,52
323
3,8
599
399
339
a)
b,
Solvent
[I],,
mole1
Toluene
Benzene
No solvent
Toluene
Toluene
23
2,15
2,3
2,3
2.3
1
)'
a,,(calc.)d) a,,(osm.)
24 OOO
25 OOO
31 800
44OOO
70 OOO
18 660
32 600
48 800
64400
15 120
[I],: initial concentration of initiator.
[l], denotes initial concentration of 1.
[l],, denotes equilibrium concentration of 1.
d, Mn(calc.) = "11, - [l],,)M/[I],, M = molecular weight of l(228).
a)
b,
I
I
I
I
I
I
6
5
4
3
2
1
in ppm.
a
Fig. 1. 'H N M R (90MHz) spectra of exo-3,4,5-trithiatetracyclo[5.5.1 .C?*6.08.12]tride~-10-ene
(1)(dicyclopentadienetrisulfide) in C6D6(30wt.4'0 solution) at 35 "C (a) and of poly(1) in C6D6
(10 w t . 4 0 solution) at 35 OC (b). TMS was used as an internal standard
Anionic polymerization of exo-3,4,5-trithiatetracyclo[5.5.1.&,6.@,'2]tride~-IO-ene. . .
2341
bridge CH,; bridgehead CH; common for norbornane and cyclopentene rings
CH) 12, 13)] differs slightly from that given in Ref. 12), because of the different conditions of measurement (C& as solvent at 90 MHz, however CS, as solvent at 60 MHz
in Ref. i2)).
In the spectrum of poly(1) the respective bands are diffused and shifted down-field
(Fig. 1 (b)). The chemical shifts of the protons in the CH groups adjacent to the sulfur
atoms appear at 6 = 3,74 and 3,83, indi~ating'~)
the presence of the two isomeric
forms cis-exo (B)and trans (C), respectively, of the fused trithiolane ring.
as;-.
.
'
ay-.
..
sy-. . .
B
i3C
'Sy-.
..
C
NMR spectra
In the 13CNMR spectrum of monomer 1(Fig. 2(a)) peaks arise at 6 = 34,2 (bridge
CH,), 35.5 (cyclopentene CH,), 40,2 and 4 3 3 (bridgehead CH), 45,O and 51,7 (CH
groups common for cyclopentene and norbornane ring), 66,O and 62,5 (CH adjacent
to sulfur atoms in the endo isomer of 1) Is).
In the spectrum of poly(1) (Fig. 2(b)), in contrast to the spectrum of the monomer,
the respective signals are diffused and shifted down-field, with the exclusion of the
signals due to the carbons linked to the sulfur atoms, which are up-field shifted.
Fig. 2. 13C r H J NMR
spectra (15 MHz) of 1 in
C6D6(30 wt.-To solution) at
42 "C (a) and of poly(1) in
C6D, (10 wt.-To solution) at
42OC (b). TMS was used as
an internal standard
130
110
90
70
50
4 in
30
pp.m.
T. Baran, A. Duda, S. Penczek
2342
Raman spectra
In the Raman spectra only the region characteristic for C-S and S-S vibrations
(0 - 750 cm I ) was analysed. The region with wave-numbers >750 cm I , due to C-C
and C-H vibrations in the hydrocarbon unit, was omitted because during the polymerization the main changes in the Raman spectra were observed in the region up to
750 cm I .
The following bands in the monomer spectrum (Fig. 3(a)) could be identified according to Emsley et al.I3):symmetric streching C-S vibrations (three medium lines at
705, 692, and 698 cm I ) , symmetric streching S-S vibrations (strongest line in the
spectrum at 514 cm I), asymmetric streching S-S vibrations (medium lines at 460 and
485 crn I ) and deformation S-S-S vibrations of the trithiolane ring: 349,309, and 273
cm I . Weak lines at 590, 413, 388, and 240 cm I are also present.
Fig. 3. Raman spectra of l ( 3 0 wt.-To
solution in C6HJ (a), of the reaction mixture
l/poly(l) (conditions [I], = 10 mol . I - ;
[l] = 3,8 mol . I - I ; solvent: C&&, T =
25 " C )(b) and of poly(1) powder at 25 "C (c).
Spectral slith-widths: (a, b) = 6 cm-I, (c) =
8 cm-I
~
I
I
700
500
I
7
'
300
Wave number in c m l
During the polymerization the intensity of the bands due to the S-S-S vibrations in
the trithiolane ring at 273, 309, 349, and 514 cm I decrease and a new very strong
band at 490 cm I appears (Fig. 3(b)). The region in the vicinity of 480 cm I is
characteristic for streching-vibrations of linear S, sequences 13). There is no new band
at 217 cm I , suggesting that during the polymerization of 1 no elemental sulfur (S,) is
formed, at least in concentrations detectable by this method (i.e. below 5 10
mol.1 I).
In the spectrum of poly(1) (Fig. 3(c)) the strong band at 490 cm I dominates. The
bands due to the trithiolane ring at 514, 349, 309, and 273 cm I are absent.
Thermodynamicsof polymerization
For the propagation of 1 a chain growth mechanism is assumed, similar to that
proposed by us previously for exo-3,4,5-trithiatricyclo[5.2.1.&*6]decane(norbornene
trisulfide) (2) lo).
Anionic polymerization of exo-3,4,5-trithiatetracyclo[5.5.1.d*6.08*'2]tride~-10ene.
. . 2343
2
\
. .-c-c
R/
S,"
\/
. . .-c-c
c-c-
R'
1 or 2
x = 1 , 2, y = 2, 3, 4 (the cation is omitted)
The standard thermodynamic parameters of equilibrium (5) were determined from
the dependence of In [1Ieqon the reciprocal of the absolute temperature (Eq. (6)).
w
s
As:
ln[l],, = -- RT
R
(AH$ AS: denote the standard enthalpy and entropy of 1 for the polymerization
in solution (toluene)). The equilibrium concentrations of 1 ([l],,) were evaluated by
using the dilatometric method (cf. Exptl. part).
dM . d
nr.?Ah
rno dp -
VI,
iM
=
rn
+--n?Ah
1
(7)
M
where mo = starting mass of the monomer, m, = mass of the solvent (toluene), dM ,
dp,d, = densities of the monomer, polymer and solvent, respectively, at the temperature of measurement, 2 r = diameter of the capillary, Ah = the change of the
meniscus level in the capillary during the polymerization at the given temperature, M
= molecular weight of the monomer.
[l],,, evaluated by means of formulae (7), changes from 2,37 mol * 1 I at 25 "C to
3,72 mole 1 I at 90°C.
A*, and AS: were calculated by using the least squares method for fitting Eq. (6)
to the experimental points (Fig. 4): AH: = - (6,6 0,6)kJ .mol I; AS: = - (29,3
2,l) J mol I K I. The standard parameters for the polymerization of 2, determined by us earlier9#lo), are given below for comparison:
A@= = - ( 5 , 8 f 0,7)kJ*mol I , AS: = -(31,4 f 2,3) Jemol '.K I .
The position of the monomer-polymer equilibrium in the polymerizations of both 1
and 2, shifts to the monomer side with increasing temperature which finally leads to
the ceiling temperature (T,). The value of T, is determined by the standard thermodynamic parameters and the starting concentration of the monomer ([l],), e.g. Eq.
-
(8).
T. Baran, A. Duda, S. Penczek
2344
T, =
s*
AS:
R
=
(8)
+ R In[l],,
gas constant
Fig. 4. Plot of the equilibrium
concentration of 1 ([l],) versus the
reciprocal of absolute temperature
29
3.0
3.1
$2
33
lo3 . T-l/K-l
Tentatively, assuming for the bulk polymerizations the same values of
wsand
AS: found for the process in toluene as solvent, we obtained T, equal to 167 and
101 O C for 1and 2, respectively.
Experimental part
r
Instruments: ' H NMR and I3C H] NMR spectra were recorded with a 90 MHz Bruker HX72 and with 15.1 MHz JEOL FX 60 spectrometers, respectively. Raman spectra were recorded
with a Coderg PHO Raman spectrometer (double monochromator) with a He-Ne laser (Spectra
Physics) emitting at 6328 A. Molecular weights were measured in dry benzene or chloroform
solutions by using a Hewlett-Packard 502 high-speed membrane osmometer.
Materials: The endo isomer of 1 was obtained from endo-dicyclopentadiene by using the
method described by Pearce et al. IZ). This compound was finally purified by sublimation i. vac.
(10 mbar). The initiator (sodium benzenethiolate) was prepared from benzenethiol and
sodium metal in benzene solution i.vac. and subsequently washed with dry benzene several
times, dried and distributed into the thin-walled phials. Crown ether, dibenzo-18-crown-6,was
prepared as it was describedI6) and sublimed i. vac. before using. The solvents, toluene and
benzene (commercial products, from POCh, Poland), were refluxed over sodium metal during
several days and than fractionated. The middle fraction was condensed over liquid Na/K alloy
i.vac. Ally1 bromide (used as a terminating agent) (from Reakhim, USSR) was purified by
distillation.
Polymerization of I
a) Dilatornetric measurements: Polymerizations were carried out in ampoules or in dilatometers i. vac. The dilatometers(Fig. 5 ) consisted of two ampoules connected by a capillary tube.
In the ampoule the thin-walled phials with sodium benzenethiolate and crown ether (mole ratio
1 : 1,l) were placed. The side arm containing a proper amount of 1 in the breakseal was sealed to
Anionic polymerization of exo-3,4,5-trithiatetracyclo[5.5.1.&.6.08,’2]tride~-10-ene.
..
2345
the dilatometer. The whole apparatus was evacuated, toluene was distilled into the lower
ampoule and the dilatometer was sealed off as indicated in Fig. 5 . Then, the phials, containing
sodium benzenethiolate and crown ether, and the breakseal of the ampoule with 1were broken.
When all components were dissolved, the resulting solution was transferred to the lower
ampoule and the upper ampoule was sealed off. Volumes of the reagents and of the solvent were
chosen in such a way that the level of the polymerizing mixture was in the capillary tube. The
volume of the dilatometer was measured previously with a microburette (Veb Glaswerke
Ilmenau, GDR) with an accuracy equal to f2J.10 ml (it equals ca. 3% of the volume
change during the polymerization in the typical feed compositions of the reaction mixture).
2
Fig. 5. Dilatometer. (l), (2): Pyrex glass ampoules,
(3): capilary tube, (4): ampoule with monomer (l),
(5): phials with initiator and crown ether, (6):glass
hammers, (7), (8): sealing off positions
3
Finally, the dilatometer was placed into a thermostat. After first 2 - 5 min, necessary to
thermostate the polymerizing mixture, the level of the solution in the capillary tube begun to
decrease due to the conversion of monomer. The positions of the level of the reacting mixture
were measured by using a kathetometer (KM-6,LOMO, USSR). The average error of the
measurements was about f 1’7’0.
The equilibrium concentration of 1at a given temperature was
evaluated from the dilatometric data (Ah, c.f. Eq. (7)). (Dprivation of Eq. (7)is given in ref?)).
The density of 1 was determined in toluene solution by using a precision pycnometer: d& =
[l ,344 - 5,9 * 10 ( t - 25)] g .cm-) (temperature t in “C).The density of poly(1) was deter(t - 25)]g .cm-3. The density of toluene was
mined in a similar way: di = [1,396 - 1,0
( t - 25)] g .~ m - ~ .
measured in a dilatometer: di = [0,862- 9,2.
b) Separation of the polymer: When the polymerization was completed (control of the
conversion degree by means of dilatometry and/or chromatography)a solution of ally1 bromide
in toluene was added to the polymerizing mixture at a given temperature. Thus, the active
centers (alkyl polysulfide anions) were converted into the inactive allylpolythio end groups. The
resulting solution of the “dead” polymer/monomer mixture in toluene was added dropwise to
cold methanol, precipitating the polymer and partially the nonreacted monomer. The monomer
was extracted from the precipitate with hot methanol (62°C). Finally, the sample of pure
polymer was dried i.vac. (10 mbar) to a constant weight.
-
T. Baran, A. Duda, S. Penczek
2346
(C&j+3),
(22834)
Calc.
Found
C 52,58
C 52,51
H 5,30
H 5,16
S 42,12
S42,13
c) Measurements of the equilibrium concentration at room temperature (25 “C):The equilibrium concentration of the polymer at room temperature was determined from the mass of the
isolated polymer (see above). The equilibrium concentration of the monomer was measured by
means of both gas chromatography and Raman spectroscopy. In the Raman measurements the
band of 1 at 309 cm-.’ was monitored. The solvent band (benzene, at 607 cm-’) was used as
internal standard.
2,
3,
4,
6,
7,
8,
9,
lo)
12)
j3)
j4)
E. R. Bertozzi, Rubber Chem. Techno]. 41, 114 (1968)
Pol. 78934 (1976); Chem. Abstr. 85, 95 537x (1976)
S. Penczek, R. Slqzak, A. Duda, Nature (London) 273, 738 (1978)
A. Duda, S . Penczek, Makromol. Chem. 181, 995 (1980)
A. Duda, S. Penczek, Macromolecules 15, 36 (1982)
A. Duda, Ph. D. Thesis, Lodi, (Poland) 1983
A. Duda. R. Szymabski, S. Penczek, J. Macromol. Sci., Chem 20, 967 (1983)
A. D. Aliev. Zh. Zhumabaev, A. Y.Koshevnik, S. L. Alieva, B. A. Krentsel, Azerb. Khim.
Zh. 3, 77 (1980); Chem. Abstr. 95, 4375Oy (1980)
A. Duda, T. Baran, V. Internationales Mikrosymposium, “Fortschritte in Ionenpolymerisation”, Prag, 1982, p. 66
T. Baran, A. Duda, S. Penczek, J. Polym. Sci., Polym. Chem. Ed. 22, 1085 (1984)
T. C. Shields, A. N. Kurtz, J. Am. Chem. SOC.91, 5415 (1969)
B. K. Bordoloi, E. M. Pearce, L. Blight, B. R. Currel, R. Merral, R. A. M. Scott, J. Polym.
Sci., Polym. Chem. Ed. 18, 383 (1980)
J. Emsley, D. W. Griffiths, G. J. J. Jayne, J. Chem. SOC.,PerkinTrans. 1: 1979, 228
J. Emsley, D. W. Griffiths, Phosphorus Sulfur 9, 227 (1980)
B. K. Bordoloi, E. M. Pearce, Adv. Chem. Ser. 165, 31 (1978)
C. J. Pedersen, J. Am. Chem. Soc. 89, 7017 (1967)