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1987 Volume 5 Issue 2
1987, 5(2): 87-94
Abstract:
The gaseous products of high temperature pyrolysis (300℃ to 960℃) of aerylonitrile polymers were measured continuously under nitrogen atmosphere by on-line Fourier Transform Infrared Spectroscopic method (FTIR). From the variations of characteristic peaks it was found that the nitrogen of macromolecules evolved were mainly in the form of hydrogen cyanide and ammonia. During the pyrolysis amorphous carbonaceous element was formed, and crosslinked to form network structure. Three kinds of samples were used for comparison.The experimental results show that the gaseous products of volatile small molecules were HCN,NH3,CH4,C2H6 and cyanide.CO and CO2 were formed when copolymers of PAN were thermally pyrolyzed.
The gaseous products of high temperature pyrolysis (300℃ to 960℃) of aerylonitrile polymers were measured continuously under nitrogen atmosphere by on-line Fourier Transform Infrared Spectroscopic method (FTIR). From the variations of characteristic peaks it was found that the nitrogen of macromolecules evolved were mainly in the form of hydrogen cyanide and ammonia. During the pyrolysis amorphous carbonaceous element was formed, and crosslinked to form network structure. Three kinds of samples were used for comparison.The experimental results show that the gaseous products of volatile small molecules were HCN,NH3,CH4,C2H6 and cyanide.CO and CO2 were formed when copolymers of PAN were thermally pyrolyzed.
1987, 5(2): 95-100
Abstract:
The salts dissolved in the amide solvent play an important role in the synthesis of high molecular weight poly(p-phenylene terephthalamide) (PPTA). The solubilization of salts was investigated in this paper. The effects of association-dissociation equilibrium of salts and the solvation of their ions as well as hydrogenbond on solubilization were discussed in some detail. The effects were attributed to cations and anions of salts respetively. Finally, the equation of solubilization was established according to the experimental results and some thermodynamic laws.The relations between molecular weight of PPTA and the solubilization were discussed.
The salts dissolved in the amide solvent play an important role in the synthesis of high molecular weight poly(p-phenylene terephthalamide) (PPTA). The solubilization of salts was investigated in this paper. The effects of association-dissociation equilibrium of salts and the solvation of their ions as well as hydrogenbond on solubilization were discussed in some detail. The effects were attributed to cations and anions of salts respetively. Finally, the equation of solubilization was established according to the experimental results and some thermodynamic laws.The relations between molecular weight of PPTA and the solubilization were discussed.
1987, 5(2): 101-108
Abstract:
The variation of the molecular weight and molecular weight distribution of cis-polybutadiene in the course of polymerization catalyzed by lanthanide complex composed of triisobutyl aluminium or diisobutyl aluminium hydride was investigated by osmometry, viscometry and size exclusion chromatography. By analyzing the experimental data, the reasons of the appearance of himodal molecular weight distribution were elucidated and the possible mechanisms of polymerization were discussed.
The variation of the molecular weight and molecular weight distribution of cis-polybutadiene in the course of polymerization catalyzed by lanthanide complex composed of triisobutyl aluminium or diisobutyl aluminium hydride was investigated by osmometry, viscometry and size exclusion chromatography. By analyzing the experimental data, the reasons of the appearance of himodal molecular weight distribution were elucidated and the possible mechanisms of polymerization were discussed.
1987, 5(2): 109-113
Abstract:
The sequence distribution and the terminal structures of poly-1,3-pentadiene chains obtained by rare earth catalyst and effect of polymerization temperature on microstructure of the polymer have been investigated by 13C-NMR method. According to experimental results it was supposed that terminal active growing chain of the polymer would be four types of anti- and syn-η3-allyl structures. When polymerization temperature was reduced, the content of cis-1,4-poly-1,3-pcntadiene increases. It can be explained by isomerization between anti-and syn-η3-allyl.The process forming trans-1,2 unit instead of 3,4-unit were also described.
The sequence distribution and the terminal structures of poly-1,3-pentadiene chains obtained by rare earth catalyst and effect of polymerization temperature on microstructure of the polymer have been investigated by 13C-NMR method. According to experimental results it was supposed that terminal active growing chain of the polymer would be four types of anti- and syn-η3-allyl structures. When polymerization temperature was reduced, the content of cis-1,4-poly-1,3-pcntadiene increases. It can be explained by isomerization between anti-and syn-η3-allyl.The process forming trans-1,2 unit instead of 3,4-unit were also described.
1987, 5(2): 114-119
Abstract:
Isoprene can be plymerized with Fe(acac)3-phen-AlEt3 catalyst system into a polymer mainly containg 3, 4-unit and capable of crystallizing to some extent. The13C-NMR spectra of 3, 4-polyisoprene synthesized: with Fe-catalyst system were investigated, and the: sequence distribution of cis-1, 4, trons-1, 4 and 3, 4-units and the amount of head-to-head and tail-to-tail linkages of 1, 4 and 3, 4-units were discussed. Results showed that the contents of cis-1, 4, trons-1, 4 and 3, 4-unit calculated from different carbon types were satis factorily identical,indicating correct assignments of these peaks.
Isoprene can be plymerized with Fe(acac)3-phen-AlEt3 catalyst system into a polymer mainly containg 3, 4-unit and capable of crystallizing to some extent. The13C-NMR spectra of 3, 4-polyisoprene synthesized: with Fe-catalyst system were investigated, and the: sequence distribution of cis-1, 4, trons-1, 4 and 3, 4-units and the amount of head-to-head and tail-to-tail linkages of 1, 4 and 3, 4-units were discussed. Results showed that the contents of cis-1, 4, trons-1, 4 and 3, 4-unit calculated from different carbon types were satis factorily identical,indicating correct assignments of these peaks.
1987, 5(2): 120-124
Abstract:
The dielectric permittivity and loss tangent of 1,2-polybutadienes with different chain structures were determined as a function of temperature from-180℃ to 100℃ at different frequencies, and the frequency and structure dependence of the dielectric propertie of 1,2-polybutadienes have been investigated. It is found that a maximum of the permittivity occurs in the glass-transition region. The width of the glasstransition peak increases with increasing frequency while its height has little change. With a rise in the content of 1,2-units,the permittivity decreases and the height of the glass-transition peak slightly grows.A maximum of the width of the glass-transition peak appears when the content of 1,2-units is about 45%.Both the permittivity and dielectric loss drop down as the growth of the content of syndiotactic 1,2-units.
The dielectric permittivity and loss tangent of 1,2-polybutadienes with different chain structures were determined as a function of temperature from-180℃ to 100℃ at different frequencies, and the frequency and structure dependence of the dielectric propertie of 1,2-polybutadienes have been investigated. It is found that a maximum of the permittivity occurs in the glass-transition region. The width of the glasstransition peak increases with increasing frequency while its height has little change. With a rise in the content of 1,2-units,the permittivity decreases and the height of the glass-transition peak slightly grows.A maximum of the width of the glass-transition peak appears when the content of 1,2-units is about 45%.Both the permittivity and dielectric loss drop down as the growth of the content of syndiotactic 1,2-units.
1987, 5(2): 125-132
Abstract:
A new kind of photostabilizers, eopolymer of 2, 2, 6, 6-tetramethyl-4-piperidinyl methacrylate and β-hydroxy-γ-(ortho-hydroxy benzoxy) propyl methacrylate, has been synthesized. The spectral behaviors of these copolymers were studied in detail. In the presence of salicylyl group a strong absorption in the region of 280—330 nm could be observed, and an unusual Stoke's shift appeared in the fluorescence spectrum excited by 310nm. The photostabilization ability of these copolymers in the process of photodegradation of cis-poly(butadiene)was studied.Results indicated that these compounds possess excellent photostabilization ability.
A new kind of photostabilizers, eopolymer of 2, 2, 6, 6-tetramethyl-4-piperidinyl methacrylate and β-hydroxy-γ-(ortho-hydroxy benzoxy) propyl methacrylate, has been synthesized. The spectral behaviors of these copolymers were studied in detail. In the presence of salicylyl group a strong absorption in the region of 280—330 nm could be observed, and an unusual Stoke's shift appeared in the fluorescence spectrum excited by 310nm. The photostabilization ability of these copolymers in the process of photodegradation of cis-poly(butadiene)was studied.Results indicated that these compounds possess excellent photostabilization ability.
1987, 5(2): 133-140
Abstract:
Chemical reactions between poly (vinyl pyridine)s and 1, 4-butanediol diglycidyl ether and other epoxy compounds were studied by Fourier transform infrared spectroscopy and other techniques. The epoxy group was found to react with the pyridine side group of poly (4-vinyl pyridine), forming crosslinked networks which contain cyclic amide structures. The reaction was also observed in the interracial region of poly(vinyl pyridine) and γ-glycidoxy propyl trimethoxysilane hydrolyzate (γ-GPS) coatings on PET fiber substrates.poly(2-vinyl pyridine)does not show the same reaction.
Chemical reactions between poly (vinyl pyridine)s and 1, 4-butanediol diglycidyl ether and other epoxy compounds were studied by Fourier transform infrared spectroscopy and other techniques. The epoxy group was found to react with the pyridine side group of poly (4-vinyl pyridine), forming crosslinked networks which contain cyclic amide structures. The reaction was also observed in the interracial region of poly(vinyl pyridine) and γ-glycidoxy propyl trimethoxysilane hydrolyzate (γ-GPS) coatings on PET fiber substrates.poly(2-vinyl pyridine)does not show the same reaction.
1987, 5(2): 141-148
Abstract:
The effects of solvent polarity on free radical copolymerization of 5-hexenoie acid and acrylonitrile at 60℃ were studied. It was observed thatas the polarity of solvents enhanced, both the copolymcrization rate and the reactivity ratios r1, r2 increased, while the alternating tendency of monomer units in copolymer chain decreased. It is believed that the solvent polarity raises the reactivities of acrylonitrile monomer and its growing chain radical, but causes no distinct variation in those of 5-hexenoic acid.
The effects of solvent polarity on free radical copolymerization of 5-hexenoie acid and acrylonitrile at 60℃ were studied. It was observed thatas the polarity of solvents enhanced, both the copolymcrization rate and the reactivity ratios r1, r2 increased, while the alternating tendency of monomer units in copolymer chain decreased. It is believed that the solvent polarity raises the reactivities of acrylonitrile monomer and its growing chain radical, but causes no distinct variation in those of 5-hexenoic acid.
1987, 5(2): 149-155
Abstract:
The polymer fiber usually possess typical uniaxial orientation. The molecular chains are symmetrically distributed around fiber axis. In this work, the orientation of molecular groups in the cross section of polyamide-6 fiber has been measured by using IR ATR method. The results indicated that the polyamide-6 fiber mainly contains α-crystalline form. The direction of hydrogen bonds of amide groups is predominately parallel with the surface in the cross section of the fiber.
The polymer fiber usually possess typical uniaxial orientation. The molecular chains are symmetrically distributed around fiber axis. In this work, the orientation of molecular groups in the cross section of polyamide-6 fiber has been measured by using IR ATR method. The results indicated that the polyamide-6 fiber mainly contains α-crystalline form. The direction of hydrogen bonds of amide groups is predominately parallel with the surface in the cross section of the fiber.
1987, 5(2): 156-161
Abstract:
Polysilane polymers containing cyclotetramethylenesilylene units were synthesized by sodium coupling of diorganodichlorosilanes in toluene. These polymers are soluble in common solvents, can be formed into a variety of shapes by molding, castihg, coating or potting. They can be crosslinked by irradiation and oxidation at moderate or room temperature.
Polysilane polymers containing cyclotetramethylenesilylene units were synthesized by sodium coupling of diorganodichlorosilanes in toluene. These polymers are soluble in common solvents, can be formed into a variety of shapes by molding, castihg, coating or potting. They can be crosslinked by irradiation and oxidation at moderate or room temperature.
1987, 5(2): 162-168
Abstract:
IR and 29Si NMR were used to determine the structures of ladderlike polymer polyphenylsilsesquioxanes (PPS). It was found that PPS with lots of defects had a wide and strong absorption band in 1000—1400 cm-1 with only one sharp peak at 1137 cm-1 while two peaks (1130 and 1045 cm-1 were observed for PPS with perfect ladderlike structure. Branching and crosslinking of PPS lead to the reduction of 1045 cm-1 peak. 29Si NMR spectra, however, showed two peaks (δ=-78 ppm and -87 ppm when δHMDS=0ppm)for defective or branched PPS.The -87 ppm peak is related to the ladderlikely constructed Si atoms and -78 ppm corresponds to defective Si atoms.PPS with defects less than 0.1% chain units was obtained by azeotropic polycondensations.
IR and 29Si NMR were used to determine the structures of ladderlike polymer polyphenylsilsesquioxanes (PPS). It was found that PPS with lots of defects had a wide and strong absorption band in 1000—1400 cm-1 with only one sharp peak at 1137 cm-1 while two peaks (1130 and 1045 cm-1 were observed for PPS with perfect ladderlike structure. Branching and crosslinking of PPS lead to the reduction of 1045 cm-1 peak. 29Si NMR spectra, however, showed two peaks (δ=-78 ppm and -87 ppm when δHMDS=0ppm)for defective or branched PPS.The -87 ppm peak is related to the ladderlikely constructed Si atoms and -78 ppm corresponds to defective Si atoms.PPS with defects less than 0.1% chain units was obtained by azeotropic polycondensations.
1987, 5(2): 169-173
Abstract:
A poly (vinyichloride-diethyl maleate) copolymer has been fractionated by repeated precipitation method. All fractions and the unfractionated sample have been characterized by viscometry, dynamic osmometry, Zimm static osmometry, light scattering and gel permeation chromatography. After correction for polydispersity, a [η]～M relationship for monodisperse polymer solutions has been obtained: [η]=1.99×10-3M0.87 (ml/g, at 25℃, in cyclohcxanone) For the copolymer solution in THF, the second virial coefficient A2 decreases as the molecular weight increases.The relationship is A2=2 slope (MnRT)-1/2.
A poly (vinyichloride-diethyl maleate) copolymer has been fractionated by repeated precipitation method. All fractions and the unfractionated sample have been characterized by viscometry, dynamic osmometry, Zimm static osmometry, light scattering and gel permeation chromatography. After correction for polydispersity, a [η]～M relationship for monodisperse polymer solutions has been obtained: [η]=1.99×10-3M0.87 (ml/g, at 25℃, in cyclohcxanone) For the copolymer solution in THF, the second virial coefficient A2 decreases as the molecular weight increases.The relationship is A2=2 slope (MnRT)-1/2.
