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Polymorphism of the crystalline and liquid crystal phases of polytrioxyethylene fumaroyl-bis-(4-oxybenzoate) specimens
Polymer. Science U.S.S.R. Vol. 31, No. 1, pp. 143-147, 1989 Printed in Poland
0032-3950/89 $ 1 0 . ~ + . 0 0 0 1990 Pmlamon Print pie
POLYMORPHISM OF THE CRYSTALLINE AND LIQUID CRYSTAL PHASES OF POLYTRIOXYETHYLENE FUMAROYL-bis-(4-OXYBENZOATE) SPECIMENS* YE. E. PASHKOVSKII, A. I. GRIGOR'EV, A. YA. VOLKOV, G. N. MATVEYEVA,V. V. ZUYEV, A. Yrr. BILIBIN, S. S. SKOROKHODOVand S. YA. FRENKEL' Institute of High Molecular Compounds, U.S.S.R. Academy of Sciences (Received 13 duly 1987)
The structure and mesomorphie properties of polytrioxyethylene fumaroyl-bis-(4-oxybenzoate) are studied by differential scanning calorimetry, polarization-optical microscopy, and X-ray analysis methods. The thermodynamic parameters of the phase transitions depend on the conditions of thermal treatment because of the polymorphism of the crystalline and liquid crystal phases. IN STUDYINGthe melting of thermotropic liquid crystal (LC) polymers with mesogenie groups in the main chain [1, 2] it was shown that the nature of the dependence of the temperature and enthalpy of melting on the crystallization temperature and the annealing time or scanning rate for LC polymers was the same as for flexible-chain nonmesomorphic polymers. It was also established that the thermodynamic parameters of the transition from the LC to the isotropic state (LC-I) is idenependent of the specimen temperature history, which can be explained by the fact that this transition occurs under condition~ of thermodynamic equilibrium. The case when equilibrium conditions in the LC-I transition are not observed and the transitilon parameters depend on the specimen thermal history has been described [3, 4]. The object of this work was to study the specimen phase transition parameter s and the structure of polytrioxyethylene fumaroyl-bis (4-oxybenzoate) (PTFOB) - i'--
"\
)'l:l_ ! ~
:.... ~?--~)C--CIr
~)
0
()
x )
?)BI ,~
as a function of the heat treatment conditions The method described by Bilibin et al. [5] was used to synthesize the compounds. The intrinsic viscosity of the spedmens at 298 K in chloroform was 0.05--0-065. The melting temperature and enthalpy and the clarification temperature were determined by differential scanning calorimetry (DSC) (on a DSM-2 instrument) and by polarization-optical microscopy (MIN-8 microscope). A DRON-3 setup was used for the X-ray studies, with ionization recording of the X-rays, and also a VIP 50-60 setup (URK-3 chamber) with photographic recording, using CuK. radiation, filtered by means of a Ni filter. * Vysokomol. soyed. A31: No. 1, 129-132, 1989.
143
Y~. E . PASHKOVSKII et aL
144
C
AU ,.
I
Bv L
s6~
1
~0J Fro. 1
/
'I
•
/
b I
r,K
_ _ ~ ............................ _ _ _ _ _ _ _ / _ _ ~ Fie. 2
FIG. 1. Thermograms of PTFOB specimensat q= 12.5 deg/min, obtained on heating original spot. imen (a) and on cooling from the isotropie molt (b). Fie. 2. X-ray patterns obtained for the original PTFOB specimen (a) and for a specimen annealed at 373 K over 21 hr (b). The DSC data showed that on heating the original specimens (obtained from solution) the thermograms have endotherms corresponding to melting (A) and the LC-I transition (B) (Fig. la), and also exothermic and endothermic peaks IB and D respectively), of area significantly less than that of peaks A and B. The origin of peaks C and D) will be explained below. The presence of a LC phase of nematic type over the temperature range between A and B (388--403 K) was established optically and X-ray methods: in the case of the PTFOB specimens a nematie schlieren-texture is observed, which is characteristic of the disordered nematics of a diffraction pattern containing only a diffusion halo. On cooling a specimen from the isotropic melt the exotherm corresponding to clarification is not reproduced (Fig. Ib), although according to polarization-optical analysis data an anisotropic melt is formed. The diffraction patterns a~d the optical textures obtained for PTFOB specimens in the region of existence of the LC-phase both on heating and on cooling almost coincide, i.e. "irreversibility" or" the LC-I transition is observed only when the calorimetric data is considered. In this connection, the problem of the thermodynamic stability of the LC-phase of the PTFOB specimens conforms to the established rule. It is known that for polymers showing monotropic mesomorphism realization of the LC-phase on heating is observed under conditions far h e m thermodynamic equilibrium, which is associated with the low degree of perfection of the crystalline structure. Roviello and Sirigu [3] showed that the change in the degree of perfection of the crystalline structure (for example, on annealing) results in a change in the mesomorphic properties of the specimens. In the ease of PKFOB specimens, as a result of annealiug a new crystalline modi-
Polytrioxyethylene fumaroyl-bis-(4-oxybcnzoate) specimens
145
fication is formed, as indicated by the X-ray patterns of Fig. 2, and also by the following values of the inter-plane distances, indicating the original crystalline structure (K-I) and the structure of a specimen melted at 393 K over hr and annealed at 373 K over 21 hr (K-II). K-I: 24-0, 4.76, 3.89, 3.48, 4.25, 2.91, and 2.83. K-II: 25-70, 12.90, 4.50, 4.05, 3-91, 3"70, 3.25, 3.00 and 2.83. The presence of crystalline phase polymorphism provides an explanation of the origin of the peaks on the thermograms (Fig. la): exotherm C colresponds to crystallization of the LC-melt with formation of the K-II modification, and the endotherm D, melting of the K-II modification. The smallness of the C and D peaks indicates that at the selected scanning rate q = 12.5 deg/min, and recrystallization takes place only partially. Figure 3 shows thermograms obtained for the original specimens at various values of the scanning rate. When q=25 and 50 deg/min theIe are only two endotherms on the thermograms (A and B). When q= 12-5 deg/min, as already said, recrystallization takes place only partially. When q= 6.2 deg/min the form of the thermogram hardly changes, and when q=3.1 deg/min, a high temperature endotherm E (410 K) appears. As follows from microscope observation the clarification temperature of the annealed speciments Ti=413 K, i.e. the endotherm E corresponds to a transition from the LCphase into the isotropic melt. The fact that the clarification temperature rises in jumps on changing the scanning rate when heat treatment is applied, indicates the formation of a LC-structure, differing from the original one, i.e. polymorphism of the LC-structure of the PTFOB specimens occurs. This rather unexpected result can be explained
c [~
-' '
3
/ ? ~ 7 I
ss3
I
l
qos
~-
r,K
FIe. 3 FIG. 4 FIG. 3. Thermograms obtained for the original PTFOB specimens at q=50 (1), 25 (2), 12.5 (3), 6-2 (4), 3"1 (5), 1"6 (6) and 0' 8 deg/min (7).
FIG. 4. X-ray patterns of specimens oriented by mechanical drawing without heat treatment (a) and of a specimen annealed at 373 K over 21 hr (b).
146
Y~. E, PASHKOVSKIIet aL
by the presence of several conformations of the repeating section of the polymer chain, which are stable at different temperatures. Figure 4a and b shows X-ray patterns corresponding to the K-I and K-II modifications for specimens oriented by mechanical drawing, cooled rapidly from the isotropic state without subsequent heat treatment (a) and annealed over 24 hr at 373 K (b). The size of the repeating part of the polymer chain in the case of modification K-I, as determined from the distance between layer lines is 24.5 A (for comparison, the completely drawn repeating part of the chain corresponds to the value 29.1 A). As follows from the X-ray patterns of Fig. 4b, in the case of the K-II modification the projection of the repeating unit on the axis of the molecule is equal to 25.6 A, while the slope of the units relative to the axis of the molecule is equal to 25 °. In the case of the K-II modification the size of the repeating part is 28.2 A, which is close to the value of the completely drawn repeating part of the chain. Accordingly, the polymorphism of the crystalline and LC-phases of the PTFOB specimens has a single cause, i.e. the correspondence of two conformations of the repeating unit, stable at different temperatures. The twisted chain conformation is stable at high temperatures, and is "frozen" as a result of rapid crystallization from solution or from the isotropic melt, with formation of the K-I modification. When this modification melts, the formation of a K-II structure becomes possible, because of the transition f r o m the frozen twisted conformation into the drawn conformation. This means that the multiplicity of peaks on the thermograms of Fig. 3 can be explained in terms of kinetics. In the case of the PTFOB specimens the LC-I transition occurs under non-equilibrium conditions, as indicated by the jump in entropy on clarification ASt as a function of the scamaing rate (Fig. 5b) and the sharp increase in clarification temperature at lower scanning rates (Fig. 5a). It is noted that in the case of a polymer based on
a
J I
t
"(1"-'~1 1
" i~
ASi , 2/rnole.K
1 I
12.5
,
I
25 q,
°
1~o. 5. T©mporatur¢ (a) and entropy (b) of clarification as a function of the scanning rate for the pekas D (1) and E (2) on the thermograms o f Fig. 3.
Synthesis and study of macromolecules of bent rod structure
147
tetraphthaloyl-bis-(4-hydroxybcnzoic) acid (THBA) with flexible aliphatic and hydroxyaliphatic fragment [6, 7] the values of T, and ziSL are independent of the scanning rate or the heat treatment conditions. The difference between the P T F O B specimens and the polymer based on T H B A is that the latter has a higher clarification temperature (T~=530-620 K). At high temperatures the conformational mobility of both the mesogenic and the flexible macromolecule fragments increases [8]. At relatively low temperatures T ~ 3 9 0 K) the conformational mobility cart be greatly decreased, which is the reason for the polymorphism of the crystalline and LC phases of the P T F O B specimens. Translated by N. STANDEN REFERENCES 1. W. R. KRGBAUM, J. Polymer Sci. Polymer Phys. Ed. 16: 883, 1978 2. Ye. E. PASHKOVSKII, T. G. LITVINA, V. G. BARANOV, A. Yu. BILIBIN and S. S. SKOROKHODOV, Vysokomol. soyed. 27: 623, 1985 (Translated in Polymer Sci. U,S.S.R. 27: 3, 699, 1985) 3. A. ROVIELLO and A. SIRIGU, Makromol. Chem. BI80: 2543, 1979 4. H. HOSHINO, J. I. JIN and R. W. LENZ, J. Appl. Polymer Sci. 29: 547, 1984 5. A. Yu. BILIBIN, V. V. ZUYEV and S. S. SKOROKHODOV, Makromolek. Chem. Rapid Commun. B6: 601, 1985 6. Ye. E. PASHKOVSKII, Dissert. Cand. Phys. Math. Sci., IVS, Akad. Nauk SSSR, Leningrad, 1985 7. A. Yu. BILIBIN, A. V. TENCOVTSEV, O. N. PIRANER, Ye. Ye. PASHKOVSKY and S. S. SKOROKHODOV, Makromol Chem. B186: 1575, 1985 8. N. S. KHOLMURADOV, Author's Dissert. Cand. Phys. Math. Sci., Akad. Nauk SSSR, Leningrad, 1984
Polymer Science U.S.S.R. Vol. 31, No. 1, pp. 147-155, 1989 Printed in Poland
0032-3950/89 $10.00+.00 1990 Pergamon Preu pie
SYNTHESIS AND STUDY OF MACROMOLECULES OF BENT ROD STRUCTURE USING MOLECULAR OPTICS* G. D. RUDKOVSKAYA, B. M. SHABSELS, ].A. BARANOVSKAYA, N. N. ULYANOVA, S. YA. LYUBINA, M. A. BEZRUKOVA, G. P. VLASOV and V. YE. ESKIN Institute of High Molecular Compounds, U.S.S.R Academy of Sciences
(Received 13 July 1987) Poly-y-benzyl-L-glutamate samples containing one of the following fragments in the molecular chain were synthesized: o-diglycylamino-diphenyl-disulphid¢, azo-bis-isobutyryl-hydrazide, decamothylonediamine. The synthesized molecules were considered to be rods with a * Vysokomol. soyod. A31: No. 1, 133-139, 1989.
0032-3950/89 $ 1 0 . ~ + . 0 0 0 1990 Pmlamon Print pie
POLYMORPHISM OF THE CRYSTALLINE AND LIQUID CRYSTAL PHASES OF POLYTRIOXYETHYLENE FUMAROYL-bis-(4-OXYBENZOATE) SPECIMENS* YE. E. PASHKOVSKII, A. I. GRIGOR'EV, A. YA. VOLKOV, G. N. MATVEYEVA,V. V. ZUYEV, A. Yrr. BILIBIN, S. S. SKOROKHODOVand S. YA. FRENKEL' Institute of High Molecular Compounds, U.S.S.R. Academy of Sciences (Received 13 duly 1987)
The structure and mesomorphie properties of polytrioxyethylene fumaroyl-bis-(4-oxybenzoate) are studied by differential scanning calorimetry, polarization-optical microscopy, and X-ray analysis methods. The thermodynamic parameters of the phase transitions depend on the conditions of thermal treatment because of the polymorphism of the crystalline and liquid crystal phases. IN STUDYINGthe melting of thermotropic liquid crystal (LC) polymers with mesogenie groups in the main chain [1, 2] it was shown that the nature of the dependence of the temperature and enthalpy of melting on the crystallization temperature and the annealing time or scanning rate for LC polymers was the same as for flexible-chain nonmesomorphic polymers. It was also established that the thermodynamic parameters of the transition from the LC to the isotropic state (LC-I) is idenependent of the specimen temperature history, which can be explained by the fact that this transition occurs under condition~ of thermodynamic equilibrium. The case when equilibrium conditions in the LC-I transition are not observed and the transitilon parameters depend on the specimen thermal history has been described [3, 4]. The object of this work was to study the specimen phase transition parameter s and the structure of polytrioxyethylene fumaroyl-bis (4-oxybenzoate) (PTFOB) - i'--
"\
)'l:l_ ! ~
:.... ~?--~)C--CIr
~)
0
()
x )
?)BI ,~
as a function of the heat treatment conditions The method described by Bilibin et al. [5] was used to synthesize the compounds. The intrinsic viscosity of the spedmens at 298 K in chloroform was 0.05--0-065. The melting temperature and enthalpy and the clarification temperature were determined by differential scanning calorimetry (DSC) (on a DSM-2 instrument) and by polarization-optical microscopy (MIN-8 microscope). A DRON-3 setup was used for the X-ray studies, with ionization recording of the X-rays, and also a VIP 50-60 setup (URK-3 chamber) with photographic recording, using CuK. radiation, filtered by means of a Ni filter. * Vysokomol. soyed. A31: No. 1, 129-132, 1989.
143
Y~. E . PASHKOVSKII et aL
144
C
AU ,.
I
Bv L
s6~
1
~0J Fro. 1
/
'I
•
/
b I
r,K
_ _ ~ ............................ _ _ _ _ _ _ _ / _ _ ~ Fie. 2
FIG. 1. Thermograms of PTFOB specimensat q= 12.5 deg/min, obtained on heating original spot. imen (a) and on cooling from the isotropie molt (b). Fie. 2. X-ray patterns obtained for the original PTFOB specimen (a) and for a specimen annealed at 373 K over 21 hr (b). The DSC data showed that on heating the original specimens (obtained from solution) the thermograms have endotherms corresponding to melting (A) and the LC-I transition (B) (Fig. la), and also exothermic and endothermic peaks IB and D respectively), of area significantly less than that of peaks A and B. The origin of peaks C and D) will be explained below. The presence of a LC phase of nematic type over the temperature range between A and B (388--403 K) was established optically and X-ray methods: in the case of the PTFOB specimens a nematie schlieren-texture is observed, which is characteristic of the disordered nematics of a diffraction pattern containing only a diffusion halo. On cooling a specimen from the isotropic melt the exotherm corresponding to clarification is not reproduced (Fig. Ib), although according to polarization-optical analysis data an anisotropic melt is formed. The diffraction patterns a~d the optical textures obtained for PTFOB specimens in the region of existence of the LC-phase both on heating and on cooling almost coincide, i.e. "irreversibility" or" the LC-I transition is observed only when the calorimetric data is considered. In this connection, the problem of the thermodynamic stability of the LC-phase of the PTFOB specimens conforms to the established rule. It is known that for polymers showing monotropic mesomorphism realization of the LC-phase on heating is observed under conditions far h e m thermodynamic equilibrium, which is associated with the low degree of perfection of the crystalline structure. Roviello and Sirigu [3] showed that the change in the degree of perfection of the crystalline structure (for example, on annealing) results in a change in the mesomorphic properties of the specimens. In the ease of PKFOB specimens, as a result of annealiug a new crystalline modi-
Polytrioxyethylene fumaroyl-bis-(4-oxybcnzoate) specimens
145
fication is formed, as indicated by the X-ray patterns of Fig. 2, and also by the following values of the inter-plane distances, indicating the original crystalline structure (K-I) and the structure of a specimen melted at 393 K over hr and annealed at 373 K over 21 hr (K-II). K-I: 24-0, 4.76, 3.89, 3.48, 4.25, 2.91, and 2.83. K-II: 25-70, 12.90, 4.50, 4.05, 3-91, 3"70, 3.25, 3.00 and 2.83. The presence of crystalline phase polymorphism provides an explanation of the origin of the peaks on the thermograms (Fig. la): exotherm C colresponds to crystallization of the LC-melt with formation of the K-II modification, and the endotherm D, melting of the K-II modification. The smallness of the C and D peaks indicates that at the selected scanning rate q = 12.5 deg/min, and recrystallization takes place only partially. Figure 3 shows thermograms obtained for the original specimens at various values of the scanning rate. When q=25 and 50 deg/min theIe are only two endotherms on the thermograms (A and B). When q= 12-5 deg/min, as already said, recrystallization takes place only partially. When q= 6.2 deg/min the form of the thermogram hardly changes, and when q=3.1 deg/min, a high temperature endotherm E (410 K) appears. As follows from microscope observation the clarification temperature of the annealed speciments Ti=413 K, i.e. the endotherm E corresponds to a transition from the LCphase into the isotropic melt. The fact that the clarification temperature rises in jumps on changing the scanning rate when heat treatment is applied, indicates the formation of a LC-structure, differing from the original one, i.e. polymorphism of the LC-structure of the PTFOB specimens occurs. This rather unexpected result can be explained
c [~
-' '
3
/ ? ~ 7 I
ss3
I
l
qos
~-
r,K
FIe. 3 FIG. 4 FIG. 3. Thermograms obtained for the original PTFOB specimens at q=50 (1), 25 (2), 12.5 (3), 6-2 (4), 3"1 (5), 1"6 (6) and 0' 8 deg/min (7).
FIG. 4. X-ray patterns of specimens oriented by mechanical drawing without heat treatment (a) and of a specimen annealed at 373 K over 21 hr (b).
146
Y~. E, PASHKOVSKIIet aL
by the presence of several conformations of the repeating section of the polymer chain, which are stable at different temperatures. Figure 4a and b shows X-ray patterns corresponding to the K-I and K-II modifications for specimens oriented by mechanical drawing, cooled rapidly from the isotropic state without subsequent heat treatment (a) and annealed over 24 hr at 373 K (b). The size of the repeating part of the polymer chain in the case of modification K-I, as determined from the distance between layer lines is 24.5 A (for comparison, the completely drawn repeating part of the chain corresponds to the value 29.1 A). As follows from the X-ray patterns of Fig. 4b, in the case of the K-II modification the projection of the repeating unit on the axis of the molecule is equal to 25.6 A, while the slope of the units relative to the axis of the molecule is equal to 25 °. In the case of the K-II modification the size of the repeating part is 28.2 A, which is close to the value of the completely drawn repeating part of the chain. Accordingly, the polymorphism of the crystalline and LC-phases of the PTFOB specimens has a single cause, i.e. the correspondence of two conformations of the repeating unit, stable at different temperatures. The twisted chain conformation is stable at high temperatures, and is "frozen" as a result of rapid crystallization from solution or from the isotropic melt, with formation of the K-I modification. When this modification melts, the formation of a K-II structure becomes possible, because of the transition f r o m the frozen twisted conformation into the drawn conformation. This means that the multiplicity of peaks on the thermograms of Fig. 3 can be explained in terms of kinetics. In the case of the PTFOB specimens the LC-I transition occurs under non-equilibrium conditions, as indicated by the jump in entropy on clarification ASt as a function of the scamaing rate (Fig. 5b) and the sharp increase in clarification temperature at lower scanning rates (Fig. 5a). It is noted that in the case of a polymer based on
a
J I
t
"(1"-'~1 1
" i~
ASi , 2/rnole.K
1 I
12.5
,
I
25 q,
°
1~o. 5. T©mporatur¢ (a) and entropy (b) of clarification as a function of the scanning rate for the pekas D (1) and E (2) on the thermograms o f Fig. 3.
Synthesis and study of macromolecules of bent rod structure
147
tetraphthaloyl-bis-(4-hydroxybcnzoic) acid (THBA) with flexible aliphatic and hydroxyaliphatic fragment [6, 7] the values of T, and ziSL are independent of the scanning rate or the heat treatment conditions. The difference between the P T F O B specimens and the polymer based on T H B A is that the latter has a higher clarification temperature (T~=530-620 K). At high temperatures the conformational mobility of both the mesogenic and the flexible macromolecule fragments increases [8]. At relatively low temperatures T ~ 3 9 0 K) the conformational mobility cart be greatly decreased, which is the reason for the polymorphism of the crystalline and LC phases of the P T F O B specimens. Translated by N. STANDEN REFERENCES 1. W. R. KRGBAUM, J. Polymer Sci. Polymer Phys. Ed. 16: 883, 1978 2. Ye. E. PASHKOVSKII, T. G. LITVINA, V. G. BARANOV, A. Yu. BILIBIN and S. S. SKOROKHODOV, Vysokomol. soyed. 27: 623, 1985 (Translated in Polymer Sci. U,S.S.R. 27: 3, 699, 1985) 3. A. ROVIELLO and A. SIRIGU, Makromol. Chem. BI80: 2543, 1979 4. H. HOSHINO, J. I. JIN and R. W. LENZ, J. Appl. Polymer Sci. 29: 547, 1984 5. A. Yu. BILIBIN, V. V. ZUYEV and S. S. SKOROKHODOV, Makromolek. Chem. Rapid Commun. B6: 601, 1985 6. Ye. E. PASHKOVSKII, Dissert. Cand. Phys. Math. Sci., IVS, Akad. Nauk SSSR, Leningrad, 1985 7. A. Yu. BILIBIN, A. V. TENCOVTSEV, O. N. PIRANER, Ye. Ye. PASHKOVSKY and S. S. SKOROKHODOV, Makromol Chem. B186: 1575, 1985 8. N. S. KHOLMURADOV, Author's Dissert. Cand. Phys. Math. Sci., Akad. Nauk SSSR, Leningrad, 1984
Polymer Science U.S.S.R. Vol. 31, No. 1, pp. 147-155, 1989 Printed in Poland
0032-3950/89 $10.00+.00 1990 Pergamon Preu pie
SYNTHESIS AND STUDY OF MACROMOLECULES OF BENT ROD STRUCTURE USING MOLECULAR OPTICS* G. D. RUDKOVSKAYA, B. M. SHABSELS, ].A. BARANOVSKAYA, N. N. ULYANOVA, S. YA. LYUBINA, M. A. BEZRUKOVA, G. P. VLASOV and V. YE. ESKIN Institute of High Molecular Compounds, U.S.S.R Academy of Sciences
(Received 13 July 1987) Poly-y-benzyl-L-glutamate samples containing one of the following fragments in the molecular chain were synthesized: o-diglycylamino-diphenyl-disulphid¢, azo-bis-isobutyryl-hydrazide, decamothylonediamine. The synthesized molecules were considered to be rods with a * Vysokomol. soyod. A31: No. 1, 133-139, 1989.