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1991 Volume 9 Issue 2
1991, 9(2): 101-107
Abstract:
The spatial distribution function and second moments of circular freely jointed chain are derived based on an analytical method. The circular Gauss chain, which is simple for long chains, is compared with the circular freely jointed chain, which is exact for short chains. It is shown that the Gauss chain model predicts a more compact configurational distribution than the exact freely jointed chain. The two chain models, however, become closer to each other when the chain length increases. It is found that the difference of the mean square radius of gyration calculated with these two chain models is a constant,independent of the chain length.
The spatial distribution function and second moments of circular freely jointed chain are derived based on an analytical method. The circular Gauss chain, which is simple for long chains, is compared with the circular freely jointed chain, which is exact for short chains. It is shown that the Gauss chain model predicts a more compact configurational distribution than the exact freely jointed chain. The two chain models, however, become closer to each other when the chain length increases. It is found that the difference of the mean square radius of gyration calculated with these two chain models is a constant,independent of the chain length.
1991, 9(2): 108-112
Abstract:
The correlation between Young's modulus of mica-filled high density polyethylene (HDPE), low density polyethylene(LDPE) and the state of dispersion of plasma-treated mica in the polymer matrices was studied. The modulus and the number average diameter of mica aggregates in matrix were determined with tensile testing and image analysis respectively. The interface structure of the filler/matrix and the bulk structure of matrix were examined through the dielectric spectrometry, differential scanning calorimetry(DSC) and dynamic viscoelastic spectrometry.The results show that the Young's modulus of the filled polyethylene depends to a great extent upon the state of dispersion of filler in matrix,but it is indeoendent of the interface structure and bulk structure.The better the dispersion,the higher the Young's modulus.
The correlation between Young's modulus of mica-filled high density polyethylene (HDPE), low density polyethylene(LDPE) and the state of dispersion of plasma-treated mica in the polymer matrices was studied. The modulus and the number average diameter of mica aggregates in matrix were determined with tensile testing and image analysis respectively. The interface structure of the filler/matrix and the bulk structure of matrix were examined through the dielectric spectrometry, differential scanning calorimetry(DSC) and dynamic viscoelastic spectrometry.The results show that the Young's modulus of the filled polyethylene depends to a great extent upon the state of dispersion of filler in matrix,but it is indeoendent of the interface structure and bulk structure.The better the dispersion,the higher the Young's modulus.
1991, 9(2): 113-119
Abstract:
The number of active centers (Cp)-t and k_p-t profiles of Solvay type TiCl3 - AlR3 (R=C2H5, i-C4H9) or Stauffer AA TiCl3-Al (C2H5)3 catalyzed 1-octene polymerization were determined by using an acetyl chloride quenching method as well as kinetic data. The results show that in the studied systems kp decreases when C_p increases, indicating the presence of two or more types of different active centers. The Cpp-t plots of the Solvay TiCl3-AlR3 systems show the presence of both stable active centers and unstable centers which decay in the polymerization process.The phenomena are explained based on a model of active center plurality.The increases of Cp in the induction periods are also discussed.
The number of active centers (Cp)-t and k_p-t profiles of Solvay type TiCl3 - AlR3 (R=C2H5, i-C4H9) or Stauffer AA TiCl3-Al (C2H5)3 catalyzed 1-octene polymerization were determined by using an acetyl chloride quenching method as well as kinetic data. The results show that in the studied systems kp decreases when C_p increases, indicating the presence of two or more types of different active centers. The Cpp-t plots of the Solvay TiCl3-AlR3 systems show the presence of both stable active centers and unstable centers which decay in the polymerization process.The phenomena are explained based on a model of active center plurality.The increases of Cp in the induction periods are also discussed.
1991, 9(2): 120-129
Abstract:
Polymeric solid electrolyte system composed of triglycidyl ether of glycerol (TGEG), diglycidyl ether of polyethylene glycol (DGEPEG)and LiClO4 salt were synthesized. In this" system the electrolyte has a pecularity that not merely can the LiClO4 provide ionic carriers, but also catalyze the crosslinking reaction without adding an usual curing agent. The effect of salt content and degree of crosslinking on the viscoelasticity and ionic conductivity were studied. Both WLF and VTF equations were used to treat the experimental data in order to elucidate the mechanism of ionic conduction.It was found that the ionic conductivity of the system is carried out through the segmental motion mechanism.However,the data must be treated with care.For example,in evaluating WLF parameters,the contribution concerned with ionic carrier generation with temperature to the conductivity must be differentiated from that concerned with segmental motion.Besides,the temperature range suitable to WLF equation must also be considered.For VTF equation,it might be inapplicable if the temperature is too low and close to the glass transition temperature of the specimen.Further study is needed in order to have a quantitative information on the limitation of these equations.
Polymeric solid electrolyte system composed of triglycidyl ether of glycerol (TGEG), diglycidyl ether of polyethylene glycol (DGEPEG)and LiClO4 salt were synthesized. In this" system the electrolyte has a pecularity that not merely can the LiClO4 provide ionic carriers, but also catalyze the crosslinking reaction without adding an usual curing agent. The effect of salt content and degree of crosslinking on the viscoelasticity and ionic conductivity were studied. Both WLF and VTF equations were used to treat the experimental data in order to elucidate the mechanism of ionic conduction.It was found that the ionic conductivity of the system is carried out through the segmental motion mechanism.However,the data must be treated with care.For example,in evaluating WLF parameters,the contribution concerned with ionic carrier generation with temperature to the conductivity must be differentiated from that concerned with segmental motion.Besides,the temperature range suitable to WLF equation must also be considered.For VTF equation,it might be inapplicable if the temperature is too low and close to the glass transition temperature of the specimen.Further study is needed in order to have a quantitative information on the limitation of these equations.
1991, 9(2): 130-136
Abstract:
The compositional homogeneity of a poly (ethylene terephthalate)-poly (tetramethylene ether) multiblock copolymer sample with low content of hard segment was examined by GPC, TLC, and solubility method. The copolymer sample was found to have a uniform composition as a function of elution volume over the major portion of sample from GPC method. However within one elution fraction, the copolymer chains, although having the same hydrodynamic volume, may have some difference in composition. Two fractions with different composition were obtained by precipitation in ethanol.Some low molar mass copolymers were also separated by a TLC technique from the copolymer sample.
The compositional homogeneity of a poly (ethylene terephthalate)-poly (tetramethylene ether) multiblock copolymer sample with low content of hard segment was examined by GPC, TLC, and solubility method. The copolymer sample was found to have a uniform composition as a function of elution volume over the major portion of sample from GPC method. However within one elution fraction, the copolymer chains, although having the same hydrodynamic volume, may have some difference in composition. Two fractions with different composition were obtained by precipitation in ethanol.Some low molar mass copolymers were also separated by a TLC technique from the copolymer sample.
1991, 9(2): 137-144
Abstract:
The molar segment mass, weight-average molar mass, and molar mass distribution of a poly-(ethylene terephthalate)-poly (tetramethylene ether) multiblock copolymer sample were determined by the methods of proton nuclear magnetic resonance, low angle laser light scattering, and gel permeation chromatography.
The molar segment mass, weight-average molar mass, and molar mass distribution of a poly-(ethylene terephthalate)-poly (tetramethylene ether) multiblock copolymer sample were determined by the methods of proton nuclear magnetic resonance, low angle laser light scattering, and gel permeation chromatography.
1991, 9(2): 145-150
Abstract:
The initiation mechanism of acrylamide (AAM)polymerization using ceric ion/acetylacetone system as an initiator has been studied. The redox polymerization was revealed by the low value of overall activation energy of AAm polymerization. The structure of free radicals formed from above-mentioned initiation sytem were detected by radical trapping and ESR spectra techniques and the end groups of polymers obtained were determined by FT-IR spectra analysis method. Based on these results the initiation mechanism is proposed.
The initiation mechanism of acrylamide (AAM)polymerization using ceric ion/acetylacetone system as an initiator has been studied. The redox polymerization was revealed by the low value of overall activation energy of AAm polymerization. The structure of free radicals formed from above-mentioned initiation sytem were detected by radical trapping and ESR spectra techniques and the end groups of polymers obtained were determined by FT-IR spectra analysis method. Based on these results the initiation mechanism is proposed.
1991, 9(2): 151-159
Abstract:
In this paper a new relation between the second virial coefficients A2, (?)w and (dVes/dC)c→0=Ks was derived from proposed model theory of concentration effects in GPC for mono-and poly-dispersed polymers. Based on this relation a new method for determination of second vifial coefficients from the combination of (dVes/dC)c→0=K3, (?)w and KH measurements was proposed.The values of A2 for mono-and poly-dispersed polystyrenes with molecular weight range from 104 to 106 in good and theta solvents were determined by proposed method.Results show that their values of A2 are in agreement with those obtained by light scattering.
In this paper a new relation between the second virial coefficients A2, (?)w and (dVes/dC)c→0=Ks was derived from proposed model theory of concentration effects in GPC for mono-and poly-dispersed polymers. Based on this relation a new method for determination of second vifial coefficients from the combination of (dVes/dC)c→0=K3, (?)w and KH measurements was proposed.The values of A2 for mono-and poly-dispersed polystyrenes with molecular weight range from 104 to 106 in good and theta solvents were determined by proposed method.Results show that their values of A2 are in agreement with those obtained by light scattering.
1991, 9(2): 160-165
Abstract:
For the polycondensation reaction of Aab Cc) type,the sol fraction for post-gel is investigated from probability consideration to approach gelation condition as a limitation.Furthermore,by means of a direct differentiation technique,a recursion formula is proposed for the evaluation of polymer moments in explicit forms for both pre-gel and post-gel.
For the polycondensation reaction of Aab Cc) type,the sol fraction for post-gel is investigated from probability consideration to approach gelation condition as a limitation.Furthermore,by means of a direct differentiation technique,a recursion formula is proposed for the evaluation of polymer moments in explicit forms for both pre-gel and post-gel.
1991, 9(2): 166-170
Abstract:
The volt-ampere (Ⅰ-Ⅴ) characteristics of the c/s-poly (phenyl acetylene) (PPA) of cis-transoidal structure has been studied in the temperature range of 253-288K. An ITO/ PPA/ Au sandwich configuration was used for the measurements. Under an applied field of less than 105V/ cm it showed ohmic behavior, while the space charge limited current (SCLC) was observed at applied fields above 5×105V/ cm. In the ohmic region a conductivity of 1.37×1016S/ cm was obtained at room temperature with an activation energy of 0.5eV.These data indicate that the conduction is not intrinsic one but is the result of thermal release of trapped carriers.In fact the data in the SCLC region treated according to the theory for a single Gaussian distribution of traps gave a mean trap energy of 0.48eV with a half-width of 4.0eV and a total density of trapping states of 5×1016/cm3.
The volt-ampere (Ⅰ-Ⅴ) characteristics of the c/s-poly (phenyl acetylene) (PPA) of cis-transoidal structure has been studied in the temperature range of 253-288K. An ITO/ PPA/ Au sandwich configuration was used for the measurements. Under an applied field of less than 105V/ cm it showed ohmic behavior, while the space charge limited current (SCLC) was observed at applied fields above 5×105V/ cm. In the ohmic region a conductivity of 1.37×1016S/ cm was obtained at room temperature with an activation energy of 0.5eV.These data indicate that the conduction is not intrinsic one but is the result of thermal release of trapped carriers.In fact the data in the SCLC region treated according to the theory for a single Gaussian distribution of traps gave a mean trap energy of 0.48eV with a half-width of 4.0eV and a total density of trapping states of 5×1016/cm3.
1991, 9(2): 171-176
Abstract:
Polymer Ru-Co bimetallic complexes have been examined by X-ray photoelectron spectroscopy.The catalyst is highly active only when the mole ratio of Co/Ru is 4: 3. The activity of catalysts does not depend on the total Co/Ru ratio, but on the surface stoichiometry of Co and Ru. When the relative intensities of Co2p and Ru3d of XPS peaks are close to each other and both are high,the catalyst exhibits its maximum activity The mechanism ofcatalytic hydroformylation has been discussed.
Polymer Ru-Co bimetallic complexes have been examined by X-ray photoelectron spectroscopy.The catalyst is highly active only when the mole ratio of Co/Ru is 4: 3. The activity of catalysts does not depend on the total Co/Ru ratio, but on the surface stoichiometry of Co and Ru. When the relative intensities of Co2p and Ru3d of XPS peaks are close to each other and both are high,the catalyst exhibits its maximum activity The mechanism ofcatalytic hydroformylation has been discussed.
CHARACTERIZATION OF BRANCHING POINT DISTRIBUTION IN THE SOL OF IRRADIATED POLYSTYRENE WITH SEC-LALLS
1991, 9(2): 177-179
Abstract:
In this paper, the change behavior of branching point distribution of irradiated polystyrene in sol has been first studied by the SEC-LALLS method. The experimental results show that branching parameter of the part with lower molecular weight in the sol changes little at the early stage of irradiation and that of the part with the higher molecular weight becomes greater with the increase in radiation dose.
In this paper, the change behavior of branching point distribution of irradiated polystyrene in sol has been first studied by the SEC-LALLS method. The experimental results show that branching parameter of the part with lower molecular weight in the sol changes little at the early stage of irradiation and that of the part with the higher molecular weight becomes greater with the increase in radiation dose.
1991, 9(2): 180-183
Abstract:
The effects of irradiation on the polyetherketone with cardo group (PEK-C) were studied. It was found that PEK-C can be crosslinked by irradiation under vacuum, while degradation reaction occurred in PEK-C at room temperature in the presence of air. Moreover. it was also found that Ts value of the crosslinked PEK-C at high temperature is higher than that at room temperature in the case of the same gel content, whose value is about 8℃ higher than that of unirradiated PEK-C. The gelation dose of PEK-C at 300℃ under vacuum is 1.5×104Gy,which is about hundred times smaller than that at room temperature.
The effects of irradiation on the polyetherketone with cardo group (PEK-C) were studied. It was found that PEK-C can be crosslinked by irradiation under vacuum, while degradation reaction occurred in PEK-C at room temperature in the presence of air. Moreover. it was also found that Ts value of the crosslinked PEK-C at high temperature is higher than that at room temperature in the case of the same gel content, whose value is about 8℃ higher than that of unirradiated PEK-C. The gelation dose of PEK-C at 300℃ under vacuum is 1.5×104Gy,which is about hundred times smaller than that at room temperature.
1991, 9(2): 184-187
Abstract:
An intermolecular 13C{1H} NOE of CCl4 in the solutions of polystyrene and polybutadiene and their copolymers was observed. The results show that the defined polymer-CCl4 interaction variable has a linear relation with the polymer composition and the difference of solubility parameters and exponentially depends on the reciprocal of temperature.
An intermolecular 13C{1H} NOE of CCl4 in the solutions of polystyrene and polybutadiene and their copolymers was observed. The results show that the defined polymer-CCl4 interaction variable has a linear relation with the polymer composition and the difference of solubility parameters and exponentially depends on the reciprocal of temperature.
