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The swelling of filled styrene-divinylbenzene copolymers
THE SWELLING OF FILLED STYRENE-DIVINYLBENZENE COPOLYMERS* Y~. S. LiPxTOV and L. M. SERGEYEVA I n s t i t u t e of the Chemistry of Macromolecular Compounds, U.S.R.I~. A c a d e m y of Sciences
(Received 16 August 1965) IT IS now known that the addition of fillers to polymers, especially rubbers, results in additional network formation. In our earlier studies [1-3] we examined the effect of a filler on structure formation in thermoplastic polymers. Study of the special features of structure formation in the case where formation of the polymer takes place simultaneously with formation of the final material is of great interest. Investigation of the conditions of formation of a crosslinked polymer in the presence of a filler would be of great value, particularly to the production of reinforced plastics. We have previously shown that the structure of a linear polymer formed in the presence of a glass surface differs from the structure of the polymer produced in the absence of a filler [4, 5]. The aim of the present work was to discover some of the specific features of formation of a crosslinked polymer in the presence of glass powder of small particle size. A number of papers has been concerned with the s t u d y of polymer networks formed in the presence of a filler [6-11]. The materials studied in these papers were exclusively vulcanizates of natural and synthetic rubbers--butadienestyrene, polyurethane etc. In these studies the kinetic theory of elasticity and the F l o r y - R e h n e r theory of swelling [12] formed the basis for investigation of the behaviour of the networks in the presence of a filler. B y making use of the well known equation of the latter theory, and making a number of assumptions, it is possible to arrive at an estimate of the number of crosslink points in the network of the filled vulcanizate, and thus to estimate the number of additional points of crosslinking due to polymer-filler interaction. It seemed of interest to apply the theory of the swelling of filled vulcanizates to the swelling of filled, erosslinked polymers that are not in the high-elastic state under the experimental conditions. EXPERIMENTAL
For this study we took copolymers of s t y r e n e and divinylbenzene prepared from reaction mixtures containing three different initial ratios of the monomers. The filler was a fraction of ground quartz glass of small particle size. The monomers and filler were placed in a glass ampoule and benzoyl peroxide (0.1% calculated on the weight of monomers) was added as the initiator. After the mixture * Vysokomol. soyed. 8: No. I1, 1895-1900, 1966. 2093
2094
Yu. S. LIPATOVand L. M. SERGEYEVA
had been degassed the ampoule was sealed off from the vacuum line and placed in a thermostat. Copolymerization was carried out at 60 °, with vigorous shaking to ensure uniform distribution of the filler in the polymer. The copolymerization time was 20-30 hr. A number of copolymers were obtained, containing 3, 10 and 15% of divinylbenzene, and with filler contents of 10, 30, 50 and 70% b y weight, corresponding to 5.33, 17.9, 32.8 and 53.1% byjkvolume. Control experiments involving extraction of test samples with boiling ]~azene showed that the degree of conversion was almost 100%. The swelling was measured gravimetrically [13]. Samples before and after swelling were weighed on a VT-200 torsion balance. Equilibrium swelling was reached in 30 hr. Experiments on the kinetics of absorption of solvent vapour b y the copolymers were carried out in an absorption apparatus with a iVfcBain balance [2]. In all cases the degree of swelling was calculated with respect to the copolymer content of the sample, i.e. on the pure copolymer without filler. RESULTS AND DISCUSSION
The Table shows the results of study of the swelling in a number of solvents of copolymers with different p r o p o r t i o n s of divinylbenzene (different chemical network densities) and with different filler contents. Values of the polymersolvent interaction parameter, #, taken from reference [13], are also given. I t is seen from the Table that the equilibrium degree of swelling, Q, is strongly dependent on the nature of the solvent, though there is no direct relationship between the variations in Q and ~. This result is similar to that obtained in reference [13]. At the same time the swelling in a thermodynamically good solvent is, on the whole, greater than,in a poor solvent. The relationships between the degree of swelling of the original, filled polymer and the nature of the solvent and density of the spatial network are normal. Attention is drawn however to the fact that incorporation of the filler leads to a more or less well defined (depending on the nature of the solvent) increase in swelling. Formal application of the F l o r y Rehner theory to these results leads to the conclusion that the effective number of points of crosslinkage in the spatial network of the polymer decrease in the presence of a filler. In a number of communications it has been reported that in the presence of a filler there is an apparent increase in the degree of swelling of vulcanizates [10, 11]. This is associated with the fact that under the influence of the solvent the bonds at the polymer-filler interface are broken and as a result of this a vacuole filled with the solvent is formed around each filler particle, resulting in considerable increase in absorption of the liquid. I f complete breakdown of the bonds at the interface occurs the swelling of a filled specimen will be equal to that of an unfilled specimen if it is calculated with respect to the filled polymer, b u t if calculated with respect to pure polymer it will be given b y the equation:
Q=v,-,=(V,o-l-~)/(1-~),
(1)
where vr is the apparent volume fraction of polymer in the swollen specimen, vr°
The swelling of filled styrene-divinylbenzene copolymers DEGREE
OF
SWELLING
OF
STYRENE
COPOLYMERS WITH
BENZENE
DVB,
% 3 3 3 3 3 3 3 3 3 3 3 10 10 10 10 10 10 10 10 10 10 10 15 15 15 15 15 15 15 15 15 15 15
DIFFERENT
2095
AMOUNTS OF D I V I N Y L -
AND FILLER.
Degree of swelling, % (volume) Solvent Ethylbenzene o-Xylene Chloroform CC14 Toluene Benzene Tetrahydrofuran Dioxan Cyclohexanone Methyl ethyl ketone Decalin Ethylbenzene o-Xylene Chloroform Toluene CC14 Benzene Tetrahydrofuran Dioxan Cyclohexanone Methyl ethyl ketone Decalin Ethylbenzene o-Xylene Chloroform Toluene CC14 Benzene Tetrahydrofuran Dioxan Cyclohexanone Methyl ethyl ketone Decalin
2.48 2-63 3.64 2.84 2.95 2.96 2.75 2.75 2.71 1 '80 1.15 1.84 2-01 2.96 2.01 1.74 2.00 2.03 2.17
5.03
17.9
32.8
53.1
3-07 3.23 5.51 4-22 2.94 3.17 3-17 3.41 3.20
3.20 3-45 6.03 4.95 3.45 3.46 3.75 3-69 3.37 1.92
5.68 7.22 12-94 7.61 6.54 5.56 7.25 7.03 5.80 2-60 1.71 3.65 5.27 8.23 2-98 5.46 4.57 4.38 5-27 2.53
0.42 0.427 0.433 0-445 0.44 0.453 0-455 0-560
o-53 0.55 0-42 0.427 0.438 0.44 0.445 o.453 0.455 0.460
1-76 1-26
2.10 2.10 3-24 1-99
1.61 2.65 1.71 1.21 1"86 1.81 1-84 1.14 1.16
2.87 2-26 2-39 2.70 1.38 1.11 1.30 1.82 1-71 3.28 1.89 1.31 2.03 2.20 2.01 1.33 1-04
1"07
1.23
1"25
0'97 1.29 1-64
1.50
3.50 3.99 7-49 6.14 4.48 4.74 4.48 4.63 3.81 2.09 1.49 2.73 3.17 5.23 2.76 4-61 3.10 3.00 3-60 1-68
1-10
1.20
1.05
1-53
1-31 2.68 2.62 4.34 2.59 2.98 2-88 2.52 2.98 2.24 1.16 1.54
2.10 3-19 4-30 6-54 2.87 3.29 3.78 4.62 4.41 3.02 1.66 1.74
1-35
2.30 2-84 3.47 2.23 3.71 2-55 2.62 3-05
2.28 2.39 3.63 2-20 2-16 2.34 2.33 2.51 1-78 1-23 1.36
0.53 0-55 0.42 0.427 0.433 0.44 0.445 0.453 0.455 0-460
0.53 0.55
its t r u e v a l u e , a n d 4 t h e v o l u m e f r a c t i o n o f t h e filler. F o r t h e case w h e r e t h e r e is p o l y m e r - f i l l e r i n t e r a c t i o n t h a t is n o t b r o k e n d o w n b y t h e s o l v e n t , a n d as a r e s u l t o f w h i c h s w e l l i n g close t o t h e p a r t i c l e s is l i m i t e d ( e q u i v a l e n t t o t h e f o r m a t i o n o f additional points of crosslinkage,) Krauss derived the following equation:
Vro/V,.= 1 - - [ 3 c (1 --vr01/~) =LVro-- 114/(1 - - 4 ) = 1 - - m 4 / ( 1 - - 4 ) ,
(2)
where m a n d c are constants. This e q u a t i o n implies a linear relationship b e t w e e n Vro/Vr a n d 4 / ( 1 - - 4 ) . I f t h e r e is a d h e s i o n Vro/V~ d e c r e a s e s w i t h i n c r e a s e i n 4 / ( 1 - - 4 ) , a n d if t h e b o n d s a t t h e i n t e r f a c e a r e b r o k e n v~o/vr i n c r e a s e s w i t h i n c r e a s e i n 4 / ( 1 - - 4 ) .
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Yu. S. LIPATOVand L. M. SE~GEYEVA
Figure 1 shows the experimental relationships between vro/v r and ¢ / ( 1 - - ~ ) obtained b y us for the styrene copolymer with 3% of divinylbenzene. The nature of the relationship was the same for the other copolymers. According to Krauss these relationships suggest partial breakdown of the bonds between the polymer and the filler, leading to increase in swelling. I f this is in fact true we cannot in this case draw any definite conclusions about change in the network density of the unswollen polymer in the presence of the filler. Let us however consider our results presented in the Table. Calculation of Q from equation (1) showed that in most cases the experimentally determined degree of swelling substantially exceeds the degree of swelling calculated b y means of equation (1), assuming complete breakdown of the bonds at the interface b y action of the solvent. This leads to the very important conclusion that although partial breakdown of bonds at
,2 fO °
s
~5
05
~ L~!
I 0'5
I I
FIG. 1. Dependence of vrolvr on ~/(1--~) for a styrene copolymer with 3% of divinylbenzene in various solvents: 1--tetrahydrofuran, 2--toluene, 3--cyclohexanone, g--methyl ethyl ketone. the interface can occur [10, 11, 14] this effect cannot fully explain the considerable increase in swelling of these filled specimens. The divergence of the degree of swelling calculated from equation (1) and the experimental value increases with increase in the filler content, as for some cases shown in Fig. 2, though to different extents for good and poor solvents. Thus the observed effects cannot be explained solely b y the formation of vacuoles around the particles of filler during swelling b u t is associated with changes in the structure of the polymer network during the course of its formation in the presence of the filler. I t is suggested that these changes are controlled b y the following two factors: 1) As in the case of formation of a thermoplastic polymer on an interracial boundary from solution, b y casting or b y polymerization, interaction of the growing polymer chains during formation of a three-dimensional network with the surface will lead to loose packing of the molecules for the reasons discussed b y us in reference [1]. This loose packing is illustrated for our present systems b y the curves of the kinetics of absorption of chloroform b y filled specimens (Fig. 3),
The swelling of filled styrene-divinylbenzene copolymers
2097
I t is seen f r o m Fig. 3 t h a t t h e r a t e of a b s o r p t i o n of t h e solvent v a p o u r a n d t h e equilibrium a b s o r p t i o n are higher in t h e filled, crosslinked p o l y m e r , in complete a g r e e m e n t w i t h the results for filled, t h e r m o p l a s t i c p o l y m e r s [2]. I n absorption from t h e v a p o u r phase the possibility of filling of t h e supposed vacuoles b y ! D
.~
n
r'L
/~t×___--× f
3
I
I
J
1
2
3
I
I
4 5 Time,hr
I
I
@
7
Fro. 2. Rate curves of absorption of chloroform from the vapour phase by a styrene
copolymer with 10% of divinylbenzene, containing various quantities of filler (~o by volume): 1--53.1; 2--32.8; 3--17.9; 4--5-03. liquid is a b s e n t a n d c o n s e q u e n t l y t h e increase in a b s o r p t i o n can in no w a y be a t t r i b u t e d to this effect. 2) T h e increase in swelling a n d loose packing in a erosslinked p o l y m e r can h o w e v e r be the result of o t h e r causes. I t is v e r y p r o b a b l e t h a t the intricate surface o f the filler forms a more defective n e t w o r k t h a n is p r o d u c e d b y p o l y m e r i z a t i o n in the absence of a filler. T h e effect of a filler on t h e efficiency of crosslinking
/
A 3 ×
5#3
/79 •, ~ / / e r
328 53.1 content, voZ %
FIG. 3. Dependence on the volume fraction of filler of the difference (A) between the degree of swelling of copolymers containing 5% and 15~o of divinylbenzene, determined experimentally and calculated by equation (1)." 1 and 2-- decalin, 5 % and 15~o, 3 and 4--chloroform, 5~o and 15~o respectively.
2098
Yu. S. Ln'ATOV and L. M. SERGEYEVA
has been reported in the case of rubbers [10], b u t here crosslinking of already formed chains occurs. In our systems chain growth occurs simultaneously with crosslinking. The very intricate surface of the filler can lead to increase in the rate of chain termination on the surface, as a result of which the network density is reduced and the network becomes more defective. The surface of the filler can evidently function as an inhibitor of network formation. This can be illustrated in the following way. We conducted experiments on the formation of a copolymer of styrene with 3 ~/o of divinylbenzene in the presence of different quantities of an inhibitor. A special method was developed in which the inhibitor could be introduced at the stage when the viscosity had already increased markedly, i.e. when a truly crosslinked network had begun to form. The products were swollen in toluene (see below): Hydroquinone content, % Q (volume).
0 2.95
0.006 3-20
0.010 3.25
0.012 3.39
It is seen from these results that the degree of swelling of the copolymers prepared in the presence of the inhibitor is higher the higher the inhibitor concentration. The inhibitor prevents formation of the same number of chemical crosslinkages as would be formed in its absence. Consequently a more defective network with few points of erosslinkage is formed, resulting in an increase in swelling. Thus the increase in the degree of swelling of filled, erosslinked polymers, in comparison with unfilled specimens, can be explained b y the simultaneous effect of the two factors mentioned above. I t is determined predominantly b y the change in the nature of the three-dimensional network formed during the course of polymerization in the presence of the filler, and not b y effects associated with breaking of bonds at the polymer-filler interface b y the action of the solvent. CONCLUSIONS
(1) A study has been made of the swelling of copolymers of styrene with 3, 10 and 15% of divinylbenzene, containing different quantities of quartz glass powder of small particle size as filler. I t was found that in most cases the degree of swelling of the crosslinked polymer prepared in the presence of the filler is increased. (2) I t is shown that increase in the degree of swelling of a erosslinked polymer in the presence of a filler cannot be caused solely b y rupture of bonds at the polymer-filler interface, b u t is dependent on change in the structure of the network formed in the presence of the filler. (3) I t .is suggested that during formation of the three-dimensional network termination of the growing chains occurs on the surface of the filler particles, resulting in formation of a more defective network and an increase in swelling. Tranalated by E. O. PHILLIPS
The adsorption of acrylic ester polymers on glass
2099
REFERENCES 1. ¥u. S. LIPATOV, Dissertation, Moscow, 1963 2. Yu. S. LIPATOV and L. M. SERGEYEVA, Dokl. Akad. Nauk Beloruss. SSR 8: 594, 1964 3. Yu. S. LIPATOV and Ya. P. VASILENKO, Sb. Adgesiya polimerov (Collected Papers. Adhesion of Polymers). p. 113, Izd. Akad. Nauk SSSR, 1963 4. T. E. LIPATOVA, V. A. BUDNIKOVA and Yu. S. LIPATOV, Vysokomol. soyed. 4: 1398, 1962 (Not translated in Polymer Science U.S.S.R.) 5. T. E. LIPATOVA, I. S. SKORYNINA and Yu. S. LIPATOV, Sb. Adgesiya polimerov. (Collected Papers. Adhesion of Polymers). p. ]23, Izd. Akad. Nauk SSSR, 1963 6. A. M. DUECIIE, J. Polymer Sci. 15: 105, 1955 7. G. KRAUSS, Rubber World 135: 254, 1956 8. B. BOONSTRA and E. DANNENBERG, Rubber Age 82: 838, 1958 9. O. LORENZ and C. PARKS, J. Polymer Sci. 50: 299, 1961 10. G. KRAUSS, J. Appl. Polymer Sei. 7: 861, 1963 11. K. BILLS and F. SALCEDO, J. Appl. Phys. 32: 2364, 1961 12. P. FLORY and ft. REHNER, J. Chem. Phys. l h 521, 1943 13. R. BOYER and R. SPENCER, J. Polymer Sci. 3: 97, 1948 14. Yu. S. LIPATOV, Dokl. Akad. Nauk SSSR 143: 1142, 1962
THE ADSORPTION OF ACRYLIC ESTER POLYMERS ON GLASS* T. M. :PoLoNSKII, I. I. MALEYEV,
M. N. SOLTYS and M. D. OPXINICH
L'vov State University
(Received 20 August 1965) MASaOMOT,ECULAR substances, which are f r e q u e n t l y used as p r o t e c t i v e coatings, come into direct c o n t a c t w i t h solid surfaces. T h e y are also used in c o n j u n c t i o n w i t h various t y p e s of fillers, which i m p r o v e their p h y s i c o m e c h a n i c a l properties. C o n s e q u e n t l y the i n t e r a c t i o n o f the macromolecules with a solid surface is an interesting problem. One o f t h e m e t h o d s o f s t u d y of this interaction a d s o r p t i o n o f macromolecules on to a solid surface from dilute solution. S t u d y o f the a d s o r p tion of m a c r o m o l e c u l a r c o m p o u n d s can in some cases yield i n f o r m a t i o n on t h e p o l y m e r - s o l i d b o d y interfacial interaction, t h u s providing a rational basis for selection of c o m p o n e n t s of composite materials. The a d s o r p t i o n of p o l y m e r s on a solid surface is distinguished b y a n u m b e r o f specific features t h a t are d e p e n d e n t on specific aspects o f t h e s t r u c t u r e a n d b e h a v i o u r o f macromolecules in solution. F o r e x a m p l e in the a d s o r p t i o n oftlnacromolecules in some instances there is a complex relationship involving molecular * Vysokomol. soyed. 8: 1%o. 11, 1901-1904, 1966.
(Received 16 August 1965) IT IS now known that the addition of fillers to polymers, especially rubbers, results in additional network formation. In our earlier studies [1-3] we examined the effect of a filler on structure formation in thermoplastic polymers. Study of the special features of structure formation in the case where formation of the polymer takes place simultaneously with formation of the final material is of great interest. Investigation of the conditions of formation of a crosslinked polymer in the presence of a filler would be of great value, particularly to the production of reinforced plastics. We have previously shown that the structure of a linear polymer formed in the presence of a glass surface differs from the structure of the polymer produced in the absence of a filler [4, 5]. The aim of the present work was to discover some of the specific features of formation of a crosslinked polymer in the presence of glass powder of small particle size. A number of papers has been concerned with the s t u d y of polymer networks formed in the presence of a filler [6-11]. The materials studied in these papers were exclusively vulcanizates of natural and synthetic rubbers--butadienestyrene, polyurethane etc. In these studies the kinetic theory of elasticity and the F l o r y - R e h n e r theory of swelling [12] formed the basis for investigation of the behaviour of the networks in the presence of a filler. B y making use of the well known equation of the latter theory, and making a number of assumptions, it is possible to arrive at an estimate of the number of crosslink points in the network of the filled vulcanizate, and thus to estimate the number of additional points of crosslinking due to polymer-filler interaction. It seemed of interest to apply the theory of the swelling of filled vulcanizates to the swelling of filled, erosslinked polymers that are not in the high-elastic state under the experimental conditions. EXPERIMENTAL
For this study we took copolymers of s t y r e n e and divinylbenzene prepared from reaction mixtures containing three different initial ratios of the monomers. The filler was a fraction of ground quartz glass of small particle size. The monomers and filler were placed in a glass ampoule and benzoyl peroxide (0.1% calculated on the weight of monomers) was added as the initiator. After the mixture * Vysokomol. soyed. 8: No. I1, 1895-1900, 1966. 2093
2094
Yu. S. LIPATOVand L. M. SERGEYEVA
had been degassed the ampoule was sealed off from the vacuum line and placed in a thermostat. Copolymerization was carried out at 60 °, with vigorous shaking to ensure uniform distribution of the filler in the polymer. The copolymerization time was 20-30 hr. A number of copolymers were obtained, containing 3, 10 and 15% of divinylbenzene, and with filler contents of 10, 30, 50 and 70% b y weight, corresponding to 5.33, 17.9, 32.8 and 53.1% byjkvolume. Control experiments involving extraction of test samples with boiling ]~azene showed that the degree of conversion was almost 100%. The swelling was measured gravimetrically [13]. Samples before and after swelling were weighed on a VT-200 torsion balance. Equilibrium swelling was reached in 30 hr. Experiments on the kinetics of absorption of solvent vapour b y the copolymers were carried out in an absorption apparatus with a iVfcBain balance [2]. In all cases the degree of swelling was calculated with respect to the copolymer content of the sample, i.e. on the pure copolymer without filler. RESULTS AND DISCUSSION
The Table shows the results of study of the swelling in a number of solvents of copolymers with different p r o p o r t i o n s of divinylbenzene (different chemical network densities) and with different filler contents. Values of the polymersolvent interaction parameter, #, taken from reference [13], are also given. I t is seen from the Table that the equilibrium degree of swelling, Q, is strongly dependent on the nature of the solvent, though there is no direct relationship between the variations in Q and ~. This result is similar to that obtained in reference [13]. At the same time the swelling in a thermodynamically good solvent is, on the whole, greater than,in a poor solvent. The relationships between the degree of swelling of the original, filled polymer and the nature of the solvent and density of the spatial network are normal. Attention is drawn however to the fact that incorporation of the filler leads to a more or less well defined (depending on the nature of the solvent) increase in swelling. Formal application of the F l o r y Rehner theory to these results leads to the conclusion that the effective number of points of crosslinkage in the spatial network of the polymer decrease in the presence of a filler. In a number of communications it has been reported that in the presence of a filler there is an apparent increase in the degree of swelling of vulcanizates [10, 11]. This is associated with the fact that under the influence of the solvent the bonds at the polymer-filler interface are broken and as a result of this a vacuole filled with the solvent is formed around each filler particle, resulting in considerable increase in absorption of the liquid. I f complete breakdown of the bonds at the interface occurs the swelling of a filled specimen will be equal to that of an unfilled specimen if it is calculated with respect to the filled polymer, b u t if calculated with respect to pure polymer it will be given b y the equation:
Q=v,-,=(V,o-l-~)/(1-~),
(1)
where vr is the apparent volume fraction of polymer in the swollen specimen, vr°
The swelling of filled styrene-divinylbenzene copolymers DEGREE
OF
SWELLING
OF
STYRENE
COPOLYMERS WITH
BENZENE
DVB,
% 3 3 3 3 3 3 3 3 3 3 3 10 10 10 10 10 10 10 10 10 10 10 15 15 15 15 15 15 15 15 15 15 15
DIFFERENT
2095
AMOUNTS OF D I V I N Y L -
AND FILLER.
Degree of swelling, % (volume) Solvent Ethylbenzene o-Xylene Chloroform CC14 Toluene Benzene Tetrahydrofuran Dioxan Cyclohexanone Methyl ethyl ketone Decalin Ethylbenzene o-Xylene Chloroform Toluene CC14 Benzene Tetrahydrofuran Dioxan Cyclohexanone Methyl ethyl ketone Decalin Ethylbenzene o-Xylene Chloroform Toluene CC14 Benzene Tetrahydrofuran Dioxan Cyclohexanone Methyl ethyl ketone Decalin
2.48 2-63 3.64 2.84 2.95 2.96 2.75 2.75 2.71 1 '80 1.15 1.84 2-01 2.96 2.01 1.74 2.00 2.03 2.17
5.03
17.9
32.8
53.1
3-07 3.23 5.51 4-22 2.94 3.17 3-17 3.41 3.20
3.20 3-45 6.03 4.95 3.45 3.46 3.75 3-69 3.37 1.92
5.68 7.22 12-94 7.61 6.54 5.56 7.25 7.03 5.80 2-60 1.71 3.65 5.27 8.23 2-98 5.46 4.57 4.38 5-27 2.53
0.42 0.427 0.433 0-445 0.44 0.453 0-455 0-560
o-53 0.55 0-42 0.427 0.438 0.44 0.445 o.453 0.455 0.460
1-76 1-26
2.10 2.10 3-24 1-99
1.61 2.65 1.71 1.21 1"86 1.81 1-84 1.14 1.16
2.87 2-26 2-39 2.70 1.38 1.11 1.30 1.82 1-71 3.28 1.89 1.31 2.03 2.20 2.01 1.33 1-04
1"07
1.23
1"25
0'97 1.29 1-64
1.50
3.50 3.99 7-49 6.14 4.48 4.74 4.48 4.63 3.81 2.09 1.49 2.73 3.17 5.23 2.76 4-61 3.10 3.00 3-60 1-68
1-10
1.20
1.05
1-53
1-31 2.68 2.62 4.34 2.59 2.98 2-88 2.52 2.98 2.24 1.16 1.54
2.10 3-19 4-30 6-54 2.87 3.29 3.78 4.62 4.41 3.02 1.66 1.74
1-35
2.30 2-84 3.47 2.23 3.71 2-55 2.62 3-05
2.28 2.39 3.63 2-20 2-16 2.34 2.33 2.51 1-78 1-23 1.36
0.53 0-55 0.42 0.427 0.433 0.44 0.445 0.453 0.455 0-460
0.53 0.55
its t r u e v a l u e , a n d 4 t h e v o l u m e f r a c t i o n o f t h e filler. F o r t h e case w h e r e t h e r e is p o l y m e r - f i l l e r i n t e r a c t i o n t h a t is n o t b r o k e n d o w n b y t h e s o l v e n t , a n d as a r e s u l t o f w h i c h s w e l l i n g close t o t h e p a r t i c l e s is l i m i t e d ( e q u i v a l e n t t o t h e f o r m a t i o n o f additional points of crosslinkage,) Krauss derived the following equation:
Vro/V,.= 1 - - [ 3 c (1 --vr01/~) =LVro-- 114/(1 - - 4 ) = 1 - - m 4 / ( 1 - - 4 ) ,
(2)
where m a n d c are constants. This e q u a t i o n implies a linear relationship b e t w e e n Vro/Vr a n d 4 / ( 1 - - 4 ) . I f t h e r e is a d h e s i o n Vro/V~ d e c r e a s e s w i t h i n c r e a s e i n 4 / ( 1 - - 4 ) , a n d if t h e b o n d s a t t h e i n t e r f a c e a r e b r o k e n v~o/vr i n c r e a s e s w i t h i n c r e a s e i n 4 / ( 1 - - 4 ) .
2096
Yu. S. LIPATOVand L. M. SE~GEYEVA
Figure 1 shows the experimental relationships between vro/v r and ¢ / ( 1 - - ~ ) obtained b y us for the styrene copolymer with 3% of divinylbenzene. The nature of the relationship was the same for the other copolymers. According to Krauss these relationships suggest partial breakdown of the bonds between the polymer and the filler, leading to increase in swelling. I f this is in fact true we cannot in this case draw any definite conclusions about change in the network density of the unswollen polymer in the presence of the filler. Let us however consider our results presented in the Table. Calculation of Q from equation (1) showed that in most cases the experimentally determined degree of swelling substantially exceeds the degree of swelling calculated b y means of equation (1), assuming complete breakdown of the bonds at the interface b y action of the solvent. This leads to the very important conclusion that although partial breakdown of bonds at
,2 fO °
s
~5
05
~ L~!
I 0'5
I I
FIG. 1. Dependence of vrolvr on ~/(1--~) for a styrene copolymer with 3% of divinylbenzene in various solvents: 1--tetrahydrofuran, 2--toluene, 3--cyclohexanone, g--methyl ethyl ketone. the interface can occur [10, 11, 14] this effect cannot fully explain the considerable increase in swelling of these filled specimens. The divergence of the degree of swelling calculated from equation (1) and the experimental value increases with increase in the filler content, as for some cases shown in Fig. 2, though to different extents for good and poor solvents. Thus the observed effects cannot be explained solely b y the formation of vacuoles around the particles of filler during swelling b u t is associated with changes in the structure of the polymer network during the course of its formation in the presence of the filler. I t is suggested that these changes are controlled b y the following two factors: 1) As in the case of formation of a thermoplastic polymer on an interracial boundary from solution, b y casting or b y polymerization, interaction of the growing polymer chains during formation of a three-dimensional network with the surface will lead to loose packing of the molecules for the reasons discussed b y us in reference [1]. This loose packing is illustrated for our present systems b y the curves of the kinetics of absorption of chloroform b y filled specimens (Fig. 3),
The swelling of filled styrene-divinylbenzene copolymers
2097
I t is seen f r o m Fig. 3 t h a t t h e r a t e of a b s o r p t i o n of t h e solvent v a p o u r a n d t h e equilibrium a b s o r p t i o n are higher in t h e filled, crosslinked p o l y m e r , in complete a g r e e m e n t w i t h the results for filled, t h e r m o p l a s t i c p o l y m e r s [2]. I n absorption from t h e v a p o u r phase the possibility of filling of t h e supposed vacuoles b y ! D
.~
n
r'L
/~t×___--× f
3
I
I
J
1
2
3
I
I
4 5 Time,hr
I
I
@
7
Fro. 2. Rate curves of absorption of chloroform from the vapour phase by a styrene
copolymer with 10% of divinylbenzene, containing various quantities of filler (~o by volume): 1--53.1; 2--32.8; 3--17.9; 4--5-03. liquid is a b s e n t a n d c o n s e q u e n t l y t h e increase in a b s o r p t i o n can in no w a y be a t t r i b u t e d to this effect. 2) T h e increase in swelling a n d loose packing in a erosslinked p o l y m e r can h o w e v e r be the result of o t h e r causes. I t is v e r y p r o b a b l e t h a t the intricate surface o f the filler forms a more defective n e t w o r k t h a n is p r o d u c e d b y p o l y m e r i z a t i o n in the absence of a filler. T h e effect of a filler on t h e efficiency of crosslinking
/
A 3 ×
5#3
/79 •, ~ / / e r
328 53.1 content, voZ %
FIG. 3. Dependence on the volume fraction of filler of the difference (A) between the degree of swelling of copolymers containing 5% and 15~o of divinylbenzene, determined experimentally and calculated by equation (1)." 1 and 2-- decalin, 5 % and 15~o, 3 and 4--chloroform, 5~o and 15~o respectively.
2098
Yu. S. Ln'ATOV and L. M. SERGEYEVA
has been reported in the case of rubbers [10], b u t here crosslinking of already formed chains occurs. In our systems chain growth occurs simultaneously with crosslinking. The very intricate surface of the filler can lead to increase in the rate of chain termination on the surface, as a result of which the network density is reduced and the network becomes more defective. The surface of the filler can evidently function as an inhibitor of network formation. This can be illustrated in the following way. We conducted experiments on the formation of a copolymer of styrene with 3 ~/o of divinylbenzene in the presence of different quantities of an inhibitor. A special method was developed in which the inhibitor could be introduced at the stage when the viscosity had already increased markedly, i.e. when a truly crosslinked network had begun to form. The products were swollen in toluene (see below): Hydroquinone content, % Q (volume).
0 2.95
0.006 3-20
0.010 3.25
0.012 3.39
It is seen from these results that the degree of swelling of the copolymers prepared in the presence of the inhibitor is higher the higher the inhibitor concentration. The inhibitor prevents formation of the same number of chemical crosslinkages as would be formed in its absence. Consequently a more defective network with few points of erosslinkage is formed, resulting in an increase in swelling. Thus the increase in the degree of swelling of filled, erosslinked polymers, in comparison with unfilled specimens, can be explained b y the simultaneous effect of the two factors mentioned above. I t is determined predominantly b y the change in the nature of the three-dimensional network formed during the course of polymerization in the presence of the filler, and not b y effects associated with breaking of bonds at the polymer-filler interface b y the action of the solvent. CONCLUSIONS
(1) A study has been made of the swelling of copolymers of styrene with 3, 10 and 15% of divinylbenzene, containing different quantities of quartz glass powder of small particle size as filler. I t was found that in most cases the degree of swelling of the crosslinked polymer prepared in the presence of the filler is increased. (2) I t is shown that increase in the degree of swelling of a erosslinked polymer in the presence of a filler cannot be caused solely b y rupture of bonds at the polymer-filler interface, b u t is dependent on change in the structure of the network formed in the presence of the filler. (3) I t .is suggested that during formation of the three-dimensional network termination of the growing chains occurs on the surface of the filler particles, resulting in formation of a more defective network and an increase in swelling. Tranalated by E. O. PHILLIPS
The adsorption of acrylic ester polymers on glass
2099
REFERENCES 1. ¥u. S. LIPATOV, Dissertation, Moscow, 1963 2. Yu. S. LIPATOV and L. M. SERGEYEVA, Dokl. Akad. Nauk Beloruss. SSR 8: 594, 1964 3. Yu. S. LIPATOV and Ya. P. VASILENKO, Sb. Adgesiya polimerov (Collected Papers. Adhesion of Polymers). p. 113, Izd. Akad. Nauk SSSR, 1963 4. T. E. LIPATOVA, V. A. BUDNIKOVA and Yu. S. LIPATOV, Vysokomol. soyed. 4: 1398, 1962 (Not translated in Polymer Science U.S.S.R.) 5. T. E. LIPATOVA, I. S. SKORYNINA and Yu. S. LIPATOV, Sb. Adgesiya polimerov. (Collected Papers. Adhesion of Polymers). p. ]23, Izd. Akad. Nauk SSSR, 1963 6. A. M. DUECIIE, J. Polymer Sci. 15: 105, 1955 7. G. KRAUSS, Rubber World 135: 254, 1956 8. B. BOONSTRA and E. DANNENBERG, Rubber Age 82: 838, 1958 9. O. LORENZ and C. PARKS, J. Polymer Sci. 50: 299, 1961 10. G. KRAUSS, J. Appl. Polymer Sei. 7: 861, 1963 11. K. BILLS and F. SALCEDO, J. Appl. Phys. 32: 2364, 1961 12. P. FLORY and ft. REHNER, J. Chem. Phys. l h 521, 1943 13. R. BOYER and R. SPENCER, J. Polymer Sci. 3: 97, 1948 14. Yu. S. LIPATOV, Dokl. Akad. Nauk SSSR 143: 1142, 1962
THE ADSORPTION OF ACRYLIC ESTER POLYMERS ON GLASS* T. M. :PoLoNSKII, I. I. MALEYEV,
M. N. SOLTYS and M. D. OPXINICH
L'vov State University
(Received 20 August 1965) MASaOMOT,ECULAR substances, which are f r e q u e n t l y used as p r o t e c t i v e coatings, come into direct c o n t a c t w i t h solid surfaces. T h e y are also used in c o n j u n c t i o n w i t h various t y p e s of fillers, which i m p r o v e their p h y s i c o m e c h a n i c a l properties. C o n s e q u e n t l y the i n t e r a c t i o n o f the macromolecules with a solid surface is an interesting problem. One o f t h e m e t h o d s o f s t u d y of this interaction a d s o r p t i o n o f macromolecules on to a solid surface from dilute solution. S t u d y o f the a d s o r p tion of m a c r o m o l e c u l a r c o m p o u n d s can in some cases yield i n f o r m a t i o n on t h e p o l y m e r - s o l i d b o d y interfacial interaction, t h u s providing a rational basis for selection of c o m p o n e n t s of composite materials. The a d s o r p t i o n of p o l y m e r s on a solid surface is distinguished b y a n u m b e r o f specific features t h a t are d e p e n d e n t on specific aspects o f t h e s t r u c t u r e a n d b e h a v i o u r o f macromolecules in solution. F o r e x a m p l e in the a d s o r p t i o n oftlnacromolecules in some instances there is a complex relationship involving molecular * Vysokomol. soyed. 8: 1%o. 11, 1901-1904, 1966.