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The mesomorphic structure formed in poly-m-toluylsilsesquioxane during polymerization
0032--$950/80]0101-0131507.5010
Polymer ScienceU.S.S.R.Vol. 22, pp. 181-137. O Pergamon Press Ltd. 1980.Printed in Poland
THE MESOMORPHIC STRUCTURE FORMED IN POLY-mTOLUYLSILSESQUIOXANE DURING POLYMERIZATION* V. S. PAPKOV, YE. S. 0BOLONKOVA,1~. ~ . IL'INA A. A. ZHDAlq0V a n d G. L. SLOm~SK~ Scientific Council a t t h e Presidium of U.S.S.R. Academy of Sciences for S y n t h e t i o Materials
(Received 3 November 1978) Electron microscopy has been used to study the structure present in the polymerizate a t various process stages of the cage-like m-toluylcyclosilsesquioxanes. A specific structural arrangement a n d order has been detected during the synthesis o f poly-m-toluyisilsesquioxane, which is a n aggregation of the fully stretched macromolecules to mesomorphic laminar formations.
THE cycle-linear polyorganosiloxanes, i.e. the polyaryl- and polyalkylarylsilsesquioxanes [1, 2] have very rigid polymer chains with a Kutm segment length of 10-20 n m in solutions [3]. These polymers have a specific morphology like a number of other rigid chain polymers. The polyalkylarylsilsesquioxanes have a mesomorpkic structure owing to a fairly dominant "parallelization" of the macromolecules which are laterally compacted; this was observed by X-ray structural analysis [4]. The respective films produced from solutions are normally opaque because of the presence of optically irregular micro-regions several microns in size [5]. The latter are thought to have various degrees of structural order. Electron microscope studies carried out on film surfaces [5] showed more orderly arranged regions, called by the authors "supermolecular" formations, to depend on the reel. wt. of the polymer or on the aggregates consisting of "bent, fibrillar" sub-structures, or of zones with a distinct parallel packing of stretched macromolecules. The supermolecular structures can form during film production from solution but also during the actual synthesis of the polymers from cyclic, cage-like organosilsesquioxanes. This feature is most distinct in the polymerization of low mol.wt, alkylphenylcyelosilsesquioxanes having a 1 : 1 ratio of alkyl to phenyl groups (alkyl -- isobutyl, isoamyl or isohexyl) and of m-toluylcyclosilsesquioxanea (TCSSO). The polymerization kinetics of the latter had been earlier investigated' by GPC [6]. The purpose of this work was the electron microscope study of the creation of mesomorphic supermolecular structures during the TCSSO polymerization. * Vysokomol. soyed. A22: 1~o. 1, 117-122, 1980. 131
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:FIG. 1. E l e c t r o n p h o t o m i c r o g r a p h s o f f r a c t u r e d s u r f a c e s a n d t h e s u r f a c e o f t h e p o l y m e m z a t e a t v a m o u s s t a g e s o f tl.e p o l y - m - t o l u y l s l l s e s q u i o x a n e s y n t h e m s . (See t e x t f o r e x p l a n a t i o n s ) .
M e s o m o r p h m s t r u c t u r e f o r m e d i n TSSO dUring p o l y m e r i z a t i o n
135
g" 5 , a m .
FIG. 1 (cont.) EXPERIMENTAL T h e s a m e TCSSO as h a d b e e n u s e d m t h e s t u d y o f t h e p o l y m e m z a t i o n k i n e t i c s [6] w a s u s e d here. I t s M n ~ 2000 a n d i t c o n s i s t e d of a m i x t u r e of Ts-T16 c a g e - h k e r i n g s a c c o r d i n g t o I R a n d G P C (T:CH3C6H~S101.5), a n d o f a polycyclie o l i g o m e r o f M >12500 (N 15~o). T h e m e t h o d o f p o l y m e r i z i n g t h e TCSSO i n a r g o n o v e r 0"2O/o w / w K O H a n d t h a t o f G P C of t h e p o l y m e r i z a t e w e r e t h e s a m e as m e a r h e r w o r k [6]. T h e e l e c t r o n m m r o s c o p i o s t u d y of t h e s t r u c t u r e p r e s e n t i n t h e p o l y m e m z a t e a t v a r i o u s s t a g e s o f t h e process m a d e u s e o f t h e r e p h c a m e t h o d . T h e s u r f a c e o f a s e c t i o n (cut, or b r e a k ) p r o d u c e d a t 20°C w a s sprayed m the VUP-2K vacuum apparatus with a carbon-platinum replica mixture which w a s w a s h e d 2 - 3 d a y s in c h l o r o f o r m t o r e m o v e a n y s a m p l e t r a c e s a n d t h e n e x a m i n e d b y means of a EVM-100 L microscope at 10,000× magnification.
RESULTS
A fairly large fracture surfaces process stage and photographs more
number of similar photo-micrographs were produced from which showed distinct snpermolecnlar formations for each several parallel samples. 'l~ais made the interpretation of the reliable.
134
V.S. PAPKGVet al.
The eh&uges which occurred during the process are evident in Fig. 1. Tho original TCSSP (monolithic mass produced by heating the TCSSO to 120°0 followed by cooling) is not shown in a picture because it was smooth or rough at the surface which is quite typical of fracturing surfaces of "structureless" glass-like materials.
O FIG. 2. The X-ray diffractionpicture produced by poly-m-toluylsilsesquioxanein the final process stage. Figure la shows the surface on a sample after a 3 rain polymerization at 220°C. One can see a picture of fan-shapecl terraces which are apparently the result of an uneven fracture through superimposed layers. This type of fracturing surface points to a laminar crystal structure; the studied polymer had a mesomorphie structure. The X-ray picture of the fully polymerized sample with an intense and sharp halo typical for the mesomorphie structme is shown in Fig. 2. One must remember the features of the TCSSO polymerization in order to understand the reasons for the photomicrograph got in our case. The TCSSO polymerization has an anionic mechanism of the consecutive additions of the original, cage-like rings to the reactive ends of ladder-like chains. T h e results of the GPC showed the loolymerizate after a 3 min duration of the process to consist of ~ 70% original oligomer and a polymer fraction with M ~ 20,000-30,0000 (judging from the position of the ridge to the peak in the chromatogram of the original TCSSO [6]). On the basis of this knowledge one can say that the picture of the fracturing surface seems to be due to the presence of micro-regions (micro-zones) iu which rod-like macromolecules, rigid at the particular mol.wt., are situated amongst the original TCSSO molecules in parallel planes and thus reinforce these zones, which prevents the development in this direction of fissures during the fracture of the sample. The lack of any distinct snpermolecular structures at this stage will however make it impossible to get any idea about the orientation of the maeromolecular axis in these zones. The supermolecular structural formations appear in the electron photomicrographs at later stages of polymerization when the polymerizate starts to become opaque (turbid). These formations are layers with their axis pointing in lateral direction (Fig. lb-e); they are most distinct when emerging in a direction near-normal to the photographing plane and therefore also to the planes of
Mesomorphic structure formed in TSSO during polymerization
135
the terraces which also can be found on the fracturing surface at this time interval of the process. The lamellae pointing in lateral direction form the basis of the assumption that t h e y form from the growing macromolecules with their chains perpendicular to the end planes of the lamellae. An increase of their thickness during the polymerization confirms that they are thus produced. This thickness is 60-70 nm after 6 min polymerization (at 220°C; Fig. lb, c) and 70-100 nm after 9 rain (Fig. ld-f). These dimensions are equivalent to the length of molecules having mol.wt, of 70,000-80,000 and 80,000-110,000 respectively (when the macromolecules have a cis-syndiotactic structure and an identity period of about 0-5 nm [1]). The polymer fractions have approximately the same mol.wt, at these stages of polymerization according to GPC. Interesting is that an increase of the process time from 6 to 9 min makes the lamellae thicker b u t also more numerous. Figure lc and d show that they thicken not only as a result of individual gcowth b u t also of fusion with each other; the latter is probably accompanied b y the macromolecules of one lamella adding on to those of the next and this m a y cause defects to form in the polymer chains. The photographs makes it clear that the lamellae are fairly long. The fact that the lamellae are well defined structures is clearly visible in Fig. If which shows the boundary between the sample surfaces and the fracture. The lamellae emerge to the sample surface and form a complex, bulky pattern; an electron photomicrograph of the surface of one of the polymerized samples is shown in Fig. lg. It is very reminiscent of that of a polymer crystal (see the monograph [7]). The external similarity in the morphology of the mesomorphic TCSSO polymer and crystalline polymers is particularly clear in the latest process stages. Figure lh-/c are photomicrographs of the fracturing surfaces of a TCSSO sample after 30 rain polymerization at 250°C.; the lamellar morphology is quite distinct as it shows furrows typical of fractures made through laminar polymer crystals [7]. The width of the furrows is mainly 7-10 nm. Such a laminar stl~tct, ure does not stop one thinking that they are formed b y macromolecules with chains pointing m the same direction as the furrows. The Figures show the polymer to be a conglomerate of laminar structures pointing in various directions in space and their orientation can be guessed from that of the furrows. The lamellae make contact with each other during growth and fuse together. Ths fusion boundaries are easily detected in the photographs as the lines passing through apices of the angles formed b y the furrows of adjacent lamellae. The contact of several lamellae produces furrows forming typical multiangular figures. These will degenerate into oval shapes where the lamellae are at a shallow angle in relation to each other. The thickness of individual lamellae ranges from 130 to 200 nm a n d Shese dimensions are those of macromolecules assumed to have a vis-syndiotactie siloxane chain conformation; the mol.wt, are in the 150,000-220,000 range. The average mol.wt, of the polymer fraction of our sample was about 180,000 according to GPC (from the position of the peak on the chromatogram). This m e a n s
136
V.S. Piexov e$ a/.
that the lamellae are produced from fully stretched macromolecules. Not excluded is the possibility of the lateral dimensions of the thickest individual lamellae to equal those of the longest macromolecules in them with those of the shortest chains inside the lamellae. This assumption is based on the fact that the lamellae can become thicker during polymerization as a result of the fusion of parallel ones which will be accompanied by macromolecules combining after growth in opposite direction, but also by the occlusion of parts of reactive end groups. The fusions of fairly large numbers of lamellae can give rise to formations being several times thicker than molecular length; such formations can also be found on examining the photographs of the fracturing surfaces.
lrIG. 3. Electron photommrographs of: a ~ a film surface; b--a fracture surface of a film
made from the benzene solutmn of poly-m-tolyuylsilsesqmox~ne. The electron microscope study thus showed that a specific, ordered structure is formed during the synthesis of the poly-m-silsesquioxane. This consists of an aggregation of completely stretched maeromoleeules to mesomorphic laminar formations; it happens only during the polymerization while the morphology of t h e films produced from polymer solutions differs and is identical with that of films produced from other polyalkylarylsilsesquloxanes. This is visible in Fig. 3a, b which are electron photomicrographs of the film surfaces of the poly-mtoluylsilsesquixane produced in a process at 250°C within 30 rain, and of the fracturing surfaces (the film was produced from a benzene solution). The photographs show typical "fibrillar" structures described before [5]. The reason for the morphological difference between the film and samples is that the latter is produced in the initial stages of the polymerization. As shown above, there is some initial stage of the process when a sufficient number of growing macromolecules will have a specific length (at which the molecules still behave like rigid rods) which ficilitates their aggregation into lamellar structures with reactive ends a t t h e surfaces. The continuation of the polymerization will produce an addition reaction of the original TCSSP molecules with these reactive ends and make the lamellae thicker, as does the fusion of growing molecules lying close together. T h e latter reaction could be the reason for the detected deviation from the e x -
Mesomorphic structure formed in TSSO during polymerization
IST
p e e r e d linear m o l . w t . - c o n v e r s i o n f u n c t i o n for a n anionic polymerization, t o w a r d s a r a p i d mol.wt, increase [6]. Such a process m e c h a n i s m will n a t u r a l l y h a v e a r a t i o of t h e r a t e of chain p r o p a g a t i o n a n d of aggregation vital to t h e c r e a t i o n of t h e u l t i m a t e m o r p h o l o g y , and also to t h e process conditions (temperature~ residual solvent in t h e TCSSO, etc.) I t was interesting to find t h a t a process with a r a p i d h e a t i n g f r o m 220 to 280°C r e d u c e d the length of the lamellae to o n l y a p a r t of t h a t illustrated in Fig. lh~k. T h e conclusion to be d r a w n f r o m all t h e a b o v e is t h a t the f o r m a t i o n of the m e s o m o r p h i c p o l y m e r s t r u c t u r e s a c c o m p a n y i n g t h e p o l y m e r i z a t i o n process has in m a n y w a y s t h e same features as the p o l y m e r i z a t i o n in which t h e r e is a simultaneous crystallization of the polymer. Translated by K. A. ALLE~ REFERENCES
1. J. F. BROWN, J. Polymer Sci. CI: 83, 1963 2. K. A. ANDRIANOV and N. N. MAKAROVA, Yysokomol. soyed. A12: 663, 1970 (Translated in Polymer Sc,. U.S.S.R. 12: 3, 747, 1970) 3. V. N. TSVETKOV, K. A. ANDRIANOV, N. N. MAKAROVA, M. G. VITOVSKAYA e$ al., Europ. Polymer J. 9: 27, 1973 4. K. A. ANDRIANOV, G. L. SLONIMSKII, S. Ya. TSVANKIN, V. S. PAPKOV et al., Vysokomol, soyed. B16: 208, 1974 (Not translated m Polymer Sci. U.S.S.R.) 5. K. A. ANDRIANOV, G. L. SLONIMSKII, V. Yu. LEVIN, V. S. PAPKOV et al., VysokomoL soyed. B15: 395, 1973 (Not translated m Polymer Sci. U.S.S.R.) 6. V. S. PAPKOV, M. N. IL'INA, N. V. PERTSOVA, N. N. MAKAROVA et al., Vysokomol. soyed. A19: 2551, 1977 (Translated in Polymer Sci. U.S.S.R. 19: 11, 2937, 1977) 7. B. VUNDERLIKH, Fizika makromolekul. Kristallicheskaya struktura, morfologiya, defekty (Maeromolecular Physics. Crystal Structure, Morphology, Defects). pp. 272, 277, 307, Izd. "Mir", 1976 8. B. WUNDERLICH, Macromolecular Physms, v. 2, Crystal Nucleations, Growth, 189, 271, 1976
Polymer ScienceU.S.S.R.Vol. 22, pp. 181-137. O Pergamon Press Ltd. 1980.Printed in Poland
THE MESOMORPHIC STRUCTURE FORMED IN POLY-mTOLUYLSILSESQUIOXANE DURING POLYMERIZATION* V. S. PAPKOV, YE. S. 0BOLONKOVA,1~. ~ . IL'INA A. A. ZHDAlq0V a n d G. L. SLOm~SK~ Scientific Council a t t h e Presidium of U.S.S.R. Academy of Sciences for S y n t h e t i o Materials
(Received 3 November 1978) Electron microscopy has been used to study the structure present in the polymerizate a t various process stages of the cage-like m-toluylcyclosilsesquioxanes. A specific structural arrangement a n d order has been detected during the synthesis o f poly-m-toluyisilsesquioxane, which is a n aggregation of the fully stretched macromolecules to mesomorphic laminar formations.
THE cycle-linear polyorganosiloxanes, i.e. the polyaryl- and polyalkylarylsilsesquioxanes [1, 2] have very rigid polymer chains with a Kutm segment length of 10-20 n m in solutions [3]. These polymers have a specific morphology like a number of other rigid chain polymers. The polyalkylarylsilsesquioxanes have a mesomorpkic structure owing to a fairly dominant "parallelization" of the macromolecules which are laterally compacted; this was observed by X-ray structural analysis [4]. The respective films produced from solutions are normally opaque because of the presence of optically irregular micro-regions several microns in size [5]. The latter are thought to have various degrees of structural order. Electron microscope studies carried out on film surfaces [5] showed more orderly arranged regions, called by the authors "supermolecular" formations, to depend on the reel. wt. of the polymer or on the aggregates consisting of "bent, fibrillar" sub-structures, or of zones with a distinct parallel packing of stretched macromolecules. The supermolecular structures can form during film production from solution but also during the actual synthesis of the polymers from cyclic, cage-like organosilsesquioxanes. This feature is most distinct in the polymerization of low mol.wt, alkylphenylcyelosilsesquioxanes having a 1 : 1 ratio of alkyl to phenyl groups (alkyl -- isobutyl, isoamyl or isohexyl) and of m-toluylcyclosilsesquioxanea (TCSSO). The polymerization kinetics of the latter had been earlier investigated' by GPC [6]. The purpose of this work was the electron microscope study of the creation of mesomorphic supermolecular structures during the TCSSO polymerization. * Vysokomol. soyed. A22: 1~o. 1, 117-122, 1980. 131
J '182
V.S.P.~KOV
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+:
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+
. +
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"+" ++'"'_+~+ +,T~+:+ ~. ++ .+\~ ++,.~.,:+.~-+.~+:
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et al.
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+
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+
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+
+
:FIG. 1. E l e c t r o n p h o t o m i c r o g r a p h s o f f r a c t u r e d s u r f a c e s a n d t h e s u r f a c e o f t h e p o l y m e m z a t e a t v a m o u s s t a g e s o f tl.e p o l y - m - t o l u y l s l l s e s q u i o x a n e s y n t h e m s . (See t e x t f o r e x p l a n a t i o n s ) .
M e s o m o r p h m s t r u c t u r e f o r m e d i n TSSO dUring p o l y m e r i z a t i o n
135
g" 5 , a m .
FIG. 1 (cont.) EXPERIMENTAL T h e s a m e TCSSO as h a d b e e n u s e d m t h e s t u d y o f t h e p o l y m e m z a t i o n k i n e t i c s [6] w a s u s e d here. I t s M n ~ 2000 a n d i t c o n s i s t e d of a m i x t u r e of Ts-T16 c a g e - h k e r i n g s a c c o r d i n g t o I R a n d G P C (T:CH3C6H~S101.5), a n d o f a polycyclie o l i g o m e r o f M >12500 (N 15~o). T h e m e t h o d o f p o l y m e r i z i n g t h e TCSSO i n a r g o n o v e r 0"2O/o w / w K O H a n d t h a t o f G P C of t h e p o l y m e r i z a t e w e r e t h e s a m e as m e a r h e r w o r k [6]. T h e e l e c t r o n m m r o s c o p i o s t u d y of t h e s t r u c t u r e p r e s e n t i n t h e p o l y m e m z a t e a t v a r i o u s s t a g e s o f t h e process m a d e u s e o f t h e r e p h c a m e t h o d . T h e s u r f a c e o f a s e c t i o n (cut, or b r e a k ) p r o d u c e d a t 20°C w a s sprayed m the VUP-2K vacuum apparatus with a carbon-platinum replica mixture which w a s w a s h e d 2 - 3 d a y s in c h l o r o f o r m t o r e m o v e a n y s a m p l e t r a c e s a n d t h e n e x a m i n e d b y means of a EVM-100 L microscope at 10,000× magnification.
RESULTS
A fairly large fracture surfaces process stage and photographs more
number of similar photo-micrographs were produced from which showed distinct snpermolecnlar formations for each several parallel samples. 'l~ais made the interpretation of the reliable.
134
V.S. PAPKGVet al.
The eh&uges which occurred during the process are evident in Fig. 1. Tho original TCSSP (monolithic mass produced by heating the TCSSO to 120°0 followed by cooling) is not shown in a picture because it was smooth or rough at the surface which is quite typical of fracturing surfaces of "structureless" glass-like materials.
O FIG. 2. The X-ray diffractionpicture produced by poly-m-toluylsilsesquioxanein the final process stage. Figure la shows the surface on a sample after a 3 rain polymerization at 220°C. One can see a picture of fan-shapecl terraces which are apparently the result of an uneven fracture through superimposed layers. This type of fracturing surface points to a laminar crystal structure; the studied polymer had a mesomorphie structure. The X-ray picture of the fully polymerized sample with an intense and sharp halo typical for the mesomorphie structme is shown in Fig. 2. One must remember the features of the TCSSO polymerization in order to understand the reasons for the photomicrograph got in our case. The TCSSO polymerization has an anionic mechanism of the consecutive additions of the original, cage-like rings to the reactive ends of ladder-like chains. T h e results of the GPC showed the loolymerizate after a 3 min duration of the process to consist of ~ 70% original oligomer and a polymer fraction with M ~ 20,000-30,0000 (judging from the position of the ridge to the peak in the chromatogram of the original TCSSO [6]). On the basis of this knowledge one can say that the picture of the fracturing surface seems to be due to the presence of micro-regions (micro-zones) iu which rod-like macromolecules, rigid at the particular mol.wt., are situated amongst the original TCSSO molecules in parallel planes and thus reinforce these zones, which prevents the development in this direction of fissures during the fracture of the sample. The lack of any distinct snpermolecular structures at this stage will however make it impossible to get any idea about the orientation of the maeromolecular axis in these zones. The supermolecular structural formations appear in the electron photomicrographs at later stages of polymerization when the polymerizate starts to become opaque (turbid). These formations are layers with their axis pointing in lateral direction (Fig. lb-e); they are most distinct when emerging in a direction near-normal to the photographing plane and therefore also to the planes of
Mesomorphic structure formed in TSSO during polymerization
135
the terraces which also can be found on the fracturing surface at this time interval of the process. The lamellae pointing in lateral direction form the basis of the assumption that t h e y form from the growing macromolecules with their chains perpendicular to the end planes of the lamellae. An increase of their thickness during the polymerization confirms that they are thus produced. This thickness is 60-70 nm after 6 min polymerization (at 220°C; Fig. lb, c) and 70-100 nm after 9 rain (Fig. ld-f). These dimensions are equivalent to the length of molecules having mol.wt, of 70,000-80,000 and 80,000-110,000 respectively (when the macromolecules have a cis-syndiotactic structure and an identity period of about 0-5 nm [1]). The polymer fractions have approximately the same mol.wt, at these stages of polymerization according to GPC. Interesting is that an increase of the process time from 6 to 9 min makes the lamellae thicker b u t also more numerous. Figure lc and d show that they thicken not only as a result of individual gcowth b u t also of fusion with each other; the latter is probably accompanied b y the macromolecules of one lamella adding on to those of the next and this m a y cause defects to form in the polymer chains. The photographs makes it clear that the lamellae are fairly long. The fact that the lamellae are well defined structures is clearly visible in Fig. If which shows the boundary between the sample surfaces and the fracture. The lamellae emerge to the sample surface and form a complex, bulky pattern; an electron photomicrograph of the surface of one of the polymerized samples is shown in Fig. lg. It is very reminiscent of that of a polymer crystal (see the monograph [7]). The external similarity in the morphology of the mesomorphic TCSSO polymer and crystalline polymers is particularly clear in the latest process stages. Figure lh-/c are photomicrographs of the fracturing surfaces of a TCSSO sample after 30 rain polymerization at 250°C.; the lamellar morphology is quite distinct as it shows furrows typical of fractures made through laminar polymer crystals [7]. The width of the furrows is mainly 7-10 nm. Such a laminar stl~tct, ure does not stop one thinking that they are formed b y macromolecules with chains pointing m the same direction as the furrows. The Figures show the polymer to be a conglomerate of laminar structures pointing in various directions in space and their orientation can be guessed from that of the furrows. The lamellae make contact with each other during growth and fuse together. Ths fusion boundaries are easily detected in the photographs as the lines passing through apices of the angles formed b y the furrows of adjacent lamellae. The contact of several lamellae produces furrows forming typical multiangular figures. These will degenerate into oval shapes where the lamellae are at a shallow angle in relation to each other. The thickness of individual lamellae ranges from 130 to 200 nm a n d Shese dimensions are those of macromolecules assumed to have a vis-syndiotactie siloxane chain conformation; the mol.wt, are in the 150,000-220,000 range. The average mol.wt, of the polymer fraction of our sample was about 180,000 according to GPC (from the position of the peak on the chromatogram). This m e a n s
136
V.S. Piexov e$ a/.
that the lamellae are produced from fully stretched macromolecules. Not excluded is the possibility of the lateral dimensions of the thickest individual lamellae to equal those of the longest macromolecules in them with those of the shortest chains inside the lamellae. This assumption is based on the fact that the lamellae can become thicker during polymerization as a result of the fusion of parallel ones which will be accompanied by macromolecules combining after growth in opposite direction, but also by the occlusion of parts of reactive end groups. The fusions of fairly large numbers of lamellae can give rise to formations being several times thicker than molecular length; such formations can also be found on examining the photographs of the fracturing surfaces.
lrIG. 3. Electron photommrographs of: a ~ a film surface; b--a fracture surface of a film
made from the benzene solutmn of poly-m-tolyuylsilsesqmox~ne. The electron microscope study thus showed that a specific, ordered structure is formed during the synthesis of the poly-m-silsesquioxane. This consists of an aggregation of completely stretched maeromoleeules to mesomorphic laminar formations; it happens only during the polymerization while the morphology of t h e films produced from polymer solutions differs and is identical with that of films produced from other polyalkylarylsilsesquloxanes. This is visible in Fig. 3a, b which are electron photomicrographs of the film surfaces of the poly-mtoluylsilsesquixane produced in a process at 250°C within 30 rain, and of the fracturing surfaces (the film was produced from a benzene solution). The photographs show typical "fibrillar" structures described before [5]. The reason for the morphological difference between the film and samples is that the latter is produced in the initial stages of the polymerization. As shown above, there is some initial stage of the process when a sufficient number of growing macromolecules will have a specific length (at which the molecules still behave like rigid rods) which ficilitates their aggregation into lamellar structures with reactive ends a t t h e surfaces. The continuation of the polymerization will produce an addition reaction of the original TCSSP molecules with these reactive ends and make the lamellae thicker, as does the fusion of growing molecules lying close together. T h e latter reaction could be the reason for the detected deviation from the e x -
Mesomorphic structure formed in TSSO during polymerization
IST
p e e r e d linear m o l . w t . - c o n v e r s i o n f u n c t i o n for a n anionic polymerization, t o w a r d s a r a p i d mol.wt, increase [6]. Such a process m e c h a n i s m will n a t u r a l l y h a v e a r a t i o of t h e r a t e of chain p r o p a g a t i o n a n d of aggregation vital to t h e c r e a t i o n of t h e u l t i m a t e m o r p h o l o g y , and also to t h e process conditions (temperature~ residual solvent in t h e TCSSO, etc.) I t was interesting to find t h a t a process with a r a p i d h e a t i n g f r o m 220 to 280°C r e d u c e d the length of the lamellae to o n l y a p a r t of t h a t illustrated in Fig. lh~k. T h e conclusion to be d r a w n f r o m all t h e a b o v e is t h a t the f o r m a t i o n of the m e s o m o r p h i c p o l y m e r s t r u c t u r e s a c c o m p a n y i n g t h e p o l y m e r i z a t i o n process has in m a n y w a y s t h e same features as the p o l y m e r i z a t i o n in which t h e r e is a simultaneous crystallization of the polymer. Translated by K. A. ALLE~ REFERENCES
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