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1989 Volume 7 Issue 1
1989, 7(1): 1-8
Abstract:
Shish kebab structure of cis-1 , 4-polybutadiene has been obtained by quiescent solution crystallization at suitable temperature. The morphology and growth mechanism of formation of shish kebab structure have been studied in detail.The higher the molecular weight the faster the sample crystallizes.
Shish kebab structure of cis-1 , 4-polybutadiene has been obtained by quiescent solution crystallization at suitable temperature. The morphology and growth mechanism of formation of shish kebab structure have been studied in detail.The higher the molecular weight the faster the sample crystallizes.
1989, 7(1): 9-15
Abstract:
Four series of copolyesters were synthesized by direct polycondonsation reaction between aromatic dicarboxylic acids and bisphenols by using tosyi chloride and N, N-dimethylformamide ( DMF ) in pyridine under mild conditions. The electron-rich hydroxyl groups of bisphenols favoured the polycondensation reaction and the order of relative reactivities of bisphenols is as follow: bisphenoI-A> hydroquinone ～ bisphenol-S> chlorohydroquinone. The mesomorphic properties of copolyesters were examined by birefringence under polarzing microscope,melt transparency,DSC and X-ray diffraction.The minimum molar fraction of mesogenic units needed for the appearance of liquid crystallinity is not higher than0.1 despite of the different varieties and lengths of the spacers studied.
Four series of copolyesters were synthesized by direct polycondonsation reaction between aromatic dicarboxylic acids and bisphenols by using tosyi chloride and N, N-dimethylformamide ( DMF ) in pyridine under mild conditions. The electron-rich hydroxyl groups of bisphenols favoured the polycondensation reaction and the order of relative reactivities of bisphenols is as follow: bisphenoI-A> hydroquinone ～ bisphenol-S> chlorohydroquinone. The mesomorphic properties of copolyesters were examined by birefringence under polarzing microscope,melt transparency,DSC and X-ray diffraction.The minimum molar fraction of mesogenic units needed for the appearance of liquid crystallinity is not higher than0.1 despite of the different varieties and lengths of the spacers studied.
1989, 7(1): 16-22
Abstract:
Different proportions of β-cydodextrin and epichlorohydrin were used to prepare a group of β-cyclodextrin polymers. The relationship between the reaction extent and the molar ratios of reactants was discussed according to the results of 1H-NMR, 13 C-NMR spectra and elemental analysis. Especially, high resolution 1H-NMR spectra were usd for studying the reaction active sites and the extent of reaction. The solubility of oil soluble drugs in water was largely improved in the presence of water-soluble β-cyclodextrin polymer.
Different proportions of β-cydodextrin and epichlorohydrin were used to prepare a group of β-cyclodextrin polymers. The relationship between the reaction extent and the molar ratios of reactants was discussed according to the results of 1H-NMR, 13 C-NMR spectra and elemental analysis. Especially, high resolution 1H-NMR spectra were usd for studying the reaction active sites and the extent of reaction. The solubility of oil soluble drugs in water was largely improved in the presence of water-soluble β-cyclodextrin polymer.
1989, 7(1): 23-30
Abstract:
The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length and the concentration of alkyl benzene sulfonic acids on the rate of degradation reaction were discussed. It was found that in the initial stage of degradation, the cyclicity ratio and the average fused ring number did not change considerably, but the percentage of uncyclized parts content varied significantly.The suitable mechanism was supposed.
The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length and the concentration of alkyl benzene sulfonic acids on the rate of degradation reaction were discussed. It was found that in the initial stage of degradation, the cyclicity ratio and the average fused ring number did not change considerably, but the percentage of uncyclized parts content varied significantly.The suitable mechanism was supposed.
1989, 7(1): 31-37
Abstract:
Since the reactivity of Me2SiCl2(Ⅰ) and ■(Ⅱ) are very different. it is difficult to cocondensate the above two monomers with sodium in general Wurtz reaction. We have proposed a modified method to prepare copolymer containing permethylpolysilane segments and cyclodisilazane units by reaction of (Ⅱ)with Na at first, then adding (Ⅰ) into the mixture to proceed with further reaction. The obtained copolysilanes are pale yellow elastic substance and soluble in common solvents. The amounts of N in the copolymers are influenced by the operating conditions of the synthetic method.The resultant products were characterized by IR,UV,NMR and elementary analysis.The highest molecular weight determined by get permeation chromatography is 60000.
Since the reactivity of Me2SiCl2(Ⅰ) and ■(Ⅱ) are very different. it is difficult to cocondensate the above two monomers with sodium in general Wurtz reaction. We have proposed a modified method to prepare copolymer containing permethylpolysilane segments and cyclodisilazane units by reaction of (Ⅱ)with Na at first, then adding (Ⅰ) into the mixture to proceed with further reaction. The obtained copolysilanes are pale yellow elastic substance and soluble in common solvents. The amounts of N in the copolymers are influenced by the operating conditions of the synthetic method.The resultant products were characterized by IR,UV,NMR and elementary analysis.The highest molecular weight determined by get permeation chromatography is 60000.
1989, 7(1): 38-44
Abstract:
Various catalysts for the polymerization ot aromatic nitriles were investigated. It was found that Lewis acid-metal is a preferable catalyst system for the polymerization of aromatic nitriles, and the polymerization rate is about 10 times faster than Lewis acid alone. The polymerization rate of benzonitrile catalyzed by Lewis acid and different metals was measured, and the activity of metals was in the following decreasing order ,magnesium, zinc, sodium, calcium. Furthermore, the polymerization of benzonitrile catalyzed by different Lewis acid and zinc was also investigated.
Various catalysts for the polymerization ot aromatic nitriles were investigated. It was found that Lewis acid-metal is a preferable catalyst system for the polymerization of aromatic nitriles, and the polymerization rate is about 10 times faster than Lewis acid alone. The polymerization rate of benzonitrile catalyzed by Lewis acid and different metals was measured, and the activity of metals was in the following decreasing order ,magnesium, zinc, sodium, calcium. Furthermore, the polymerization of benzonitrile catalyzed by different Lewis acid and zinc was also investigated.
1989, 7(1): 45-53
Abstract:
Four new paranmeters, and , and have been proposed to describe the average length of the sequence of substituted anhydroglucose units and that of unsubstituted ones respectively along the CMC chain. The methods for determining those parameters have also been presented . Six CMC samples have been characterized in terms of intrinsic viscosity, degree of substitution (DS), index of substitution(SI) and . It has been proved experimentally that, not only can describe the sequence distribution along the CMC chain,but also can be used for calculating SI and estimating the average degree of substitution in the substituted glucose rings.
Four new paranmeters, and , and have been proposed to describe the average length of the sequence of substituted anhydroglucose units and that of unsubstituted ones respectively along the CMC chain. The methods for determining those parameters have also been presented . Six CMC samples have been characterized in terms of intrinsic viscosity, degree of substitution (DS), index of substitution(SI) and . It has been proved experimentally that, not only can describe the sequence distribution along the CMC chain,but also can be used for calculating SI and estimating the average degree of substitution in the substituted glucose rings.
1989, 7(1): 54-65
Abstract:
Polyamide 1010 is a γ-radiation crosslinkable polymer. After irradiation, it is possible to raise its service temperature up to 240℃ . Network formation greatly changes the crystallization behaviour of the polymer. In the present work, DSC was used to examine its isothermal crystallization kinetics. It is found that in addition to the necessity of more undercooling and the lowering of crystallization rate, the primary crystallization stage of the irradiated polymer is shortened. This effect is more evident increasing radiation dose and content of enhanced difunctional crosslinking agent.However,the crystallization mechanism of the orimary stage is not changed as evidenced by the constancy of Avrami exponent.The lamella end surface free energy σecalculated according to Hoffman's equation is very sensitive to γ-radiation.It increases abruptly in 2-3 fold even though the radiation dose is not high enough.The origin of this phenomenon may be accounted for in terms of network structure of the polymer.
Polyamide 1010 is a γ-radiation crosslinkable polymer. After irradiation, it is possible to raise its service temperature up to 240℃ . Network formation greatly changes the crystallization behaviour of the polymer. In the present work, DSC was used to examine its isothermal crystallization kinetics. It is found that in addition to the necessity of more undercooling and the lowering of crystallization rate, the primary crystallization stage of the irradiated polymer is shortened. This effect is more evident increasing radiation dose and content of enhanced difunctional crosslinking agent.However,the crystallization mechanism of the orimary stage is not changed as evidenced by the constancy of Avrami exponent.The lamella end surface free energy σecalculated according to Hoffman's equation is very sensitive to γ-radiation.It increases abruptly in 2-3 fold even though the radiation dose is not high enough.The origin of this phenomenon may be accounted for in terms of network structure of the polymer.
1989, 7(1): 66-74
Abstract:
The kinetics of phase transitions including a transition between mesophases were studied for a main-chain thermotropic polyester by means of DSC and depolarizing transmittance techniques. The isothermal process of these transitions was found to be described by the Avrami equation to high conversions. The Avrami exponents n are about 2,4, 5.3 and 2.2 for liquid crystallization, transition between mesophases and crystallization from mesophase respectively. The liquid crystallization from isotropic liquid phase occurs at very low undercoolings with high transformation rate.This behavior is explained as the results of the smaller value of the surface free energy for mesophase than that for crystallites which is evidenced by the very weak temperature dependence of liquid crystallization rate.
The kinetics of phase transitions including a transition between mesophases were studied for a main-chain thermotropic polyester by means of DSC and depolarizing transmittance techniques. The isothermal process of these transitions was found to be described by the Avrami equation to high conversions. The Avrami exponents n are about 2,4, 5.3 and 2.2 for liquid crystallization, transition between mesophases and crystallization from mesophase respectively. The liquid crystallization from isotropic liquid phase occurs at very low undercoolings with high transformation rate.This behavior is explained as the results of the smaller value of the surface free energy for mesophase than that for crystallites which is evidenced by the very weak temperature dependence of liquid crystallization rate.
1989, 7(1): 75-82
Abstract:
A new synthetic route to polyamides and hydroxyl polyamides was established, based on the selecting (?)-acylation of three novel typical active diesters: the active diester of N-hydroxy- (?) 4-epoxy-5-cyclohexene-2, 3-dicarboximide( HOEC), such as N, N'-(temphthaloyldioxy) bis(1, 4- epoxy - 5 - cyclohexene- 2, 3 - dicarboximide.) ( PBOEC), N, N'- ( isophthaloyl - dioxy) bis (1,4-epoxy-5-cyclohexene-2, 3-dicarboximide)(IPBOEC) and N, N' -(adipoyldioxy) his (1,4-epoxy-5-cyclohexene-2, 3-dicarboximide) ( ADOEC)with aliphatic diamines and 1,3-diamino-2-hydroxypropane.The polycondensation occurs at room temperature in solution without added catalyst.Dipolar aprotic solvents solvents which include dimethyl sulfoxide,N-methyl-2-pyrrolidone and dimethylformamide were used as solvents for polymerization.The selective N-acylation of two active diesters was performed as a model reaction study.
A new synthetic route to polyamides and hydroxyl polyamides was established, based on the selecting (?)-acylation of three novel typical active diesters: the active diester of N-hydroxy- (?) 4-epoxy-5-cyclohexene-2, 3-dicarboximide( HOEC), such as N, N'-(temphthaloyldioxy) bis(1, 4- epoxy - 5 - cyclohexene- 2, 3 - dicarboximide.) ( PBOEC), N, N'- ( isophthaloyl - dioxy) bis (1,4-epoxy-5-cyclohexene-2, 3-dicarboximide)(IPBOEC) and N, N' -(adipoyldioxy) his (1,4-epoxy-5-cyclohexene-2, 3-dicarboximide) ( ADOEC)with aliphatic diamines and 1,3-diamino-2-hydroxypropane.The polycondensation occurs at room temperature in solution without added catalyst.Dipolar aprotic solvents solvents which include dimethyl sulfoxide,N-methyl-2-pyrrolidone and dimethylformamide were used as solvents for polymerization.The selective N-acylation of two active diesters was performed as a model reaction study.
1989, 7(1): 83-89
Abstract:
There was phase separation between the anisotropic and isotropic phases in the ethyl-acetyl cellulose/dichloroacetic acid cholesteric liquid crystalline solutions .The textures of mesophase varied with the concentration. The mesophases could form the disc-like texture, oily streaks texture and texture of domains gathered randomly. In the first two textures the layers of the ordered molecular chain were perpendicular to the slide surface and the axes of the helical structure were parallel to the slide surface.
There was phase separation between the anisotropic and isotropic phases in the ethyl-acetyl cellulose/dichloroacetic acid cholesteric liquid crystalline solutions .The textures of mesophase varied with the concentration. The mesophases could form the disc-like texture, oily streaks texture and texture of domains gathered randomly. In the first two textures the layers of the ordered molecular chain were perpendicular to the slide surface and the axes of the helical structure were parallel to the slide surface.
1989, 7(1): 90-96
Abstract:
This paper is concerned with the synthesis of poly (ether-urethane) with pendant amino groups. The copolyether produced by ring opening copolymerization of tetrahydrofuran and epibromohydrin was treated with sodium azide in dimethylformamide to form azido substituted copolyether. The poly (ether-urethane) made from it was subjected to reduction reaction to convert azido group to amino group. The stress-strain behavior and dynamic-mechanical properties of poly (ether-urethane) containing pendant amino groups were studied.
This paper is concerned with the synthesis of poly (ether-urethane) with pendant amino groups. The copolyether produced by ring opening copolymerization of tetrahydrofuran and epibromohydrin was treated with sodium azide in dimethylformamide to form azido substituted copolyether. The poly (ether-urethane) made from it was subjected to reduction reaction to convert azido group to amino group. The stress-strain behavior and dynamic-mechanical properties of poly (ether-urethane) containing pendant amino groups were studied.
