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1997 Volume 15 Issue 2
1997, 15(2): 97-107
Abstract:
A full-relaxation optimization of molecule and the Dreiding force field are employed toobtain the geometry parameters and the conformational energy surfaces of meso or racemicdyad of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Three differentcarbonyl-bond orientations of side-groups resulted in the differences in depth of potentialwells in their energetic contours for a meso or a racemic dyad. These discrepancies areinterpreted as a result of various fine structures corresponding to grid search conformations as the as thereby different interactions.The analysis on the most stable conformations of PMAA confirmed that the ester groups are nearly perpendicular to the plane defined by the two adjacent skeletal bonds but may possibly change their relative orientations to meet the requirement of lower energy during the conformational state transition.For each polymer,two global energy maps of a meso and a racemic dyad were finally constructed from the superposition of energy data for the three kinds of side-group orientations by the Boltzmann factors.From an ensemble average,the proposed scheme with three rotational isomeric states(RIS) allowed us to access the experimentally unperturbed dimensions of PAA chain via the configurational statistical mechanics.Although the calculation was based on the short-range,local interactions,it was interested to note that the experimental characteristic ratios just fell within the range calculated for atactic chains.
A full-relaxation optimization of molecule and the Dreiding force field are employed toobtain the geometry parameters and the conformational energy surfaces of meso or racemicdyad of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Three differentcarbonyl-bond orientations of side-groups resulted in the differences in depth of potentialwells in their energetic contours for a meso or a racemic dyad. These discrepancies areinterpreted as a result of various fine structures corresponding to grid search conformations as the as thereby different interactions.The analysis on the most stable conformations of PMAA confirmed that the ester groups are nearly perpendicular to the plane defined by the two adjacent skeletal bonds but may possibly change their relative orientations to meet the requirement of lower energy during the conformational state transition.For each polymer,two global energy maps of a meso and a racemic dyad were finally constructed from the superposition of energy data for the three kinds of side-group orientations by the Boltzmann factors.From an ensemble average,the proposed scheme with three rotational isomeric states(RIS) allowed us to access the experimentally unperturbed dimensions of PAA chain via the configurational statistical mechanics.Although the calculation was based on the short-range,local interactions,it was interested to note that the experimental characteristic ratios just fell within the range calculated for atactic chains.
1997, 15(2): 108-113
Abstract:
The emeraldine base form of polyaniline (PANI) can be doped by a photo-induceddoping method. In this method a copolymer of vinylidene chloride and methyl acrylate(VCMAC) was used as photo acid generator which can release proton when it is exposedto ultraviolet light (λ= 254 nm). The structure of PANI-VCMAC system before and afterirradiation was characterized by elemental analysis, IR, XPS, and SEM images. Resultsobtained indicate that the photo-induced doping characteristics, such as doping position and type of charge carriers,are similar to that of PANI doped with HCl.The poor room-temperature conductivity (～10-5S/cm) of PANI-VCMAC system after irradiation may be due to low doping degree (～pH=3)and the difference in morphology as compared with PANI-HCl film.
The emeraldine base form of polyaniline (PANI) can be doped by a photo-induceddoping method. In this method a copolymer of vinylidene chloride and methyl acrylate(VCMAC) was used as photo acid generator which can release proton when it is exposedto ultraviolet light (λ= 254 nm). The structure of PANI-VCMAC system before and afterirradiation was characterized by elemental analysis, IR, XPS, and SEM images. Resultsobtained indicate that the photo-induced doping characteristics, such as doping position and type of charge carriers,are similar to that of PANI doped with HCl.The poor room-temperature conductivity (～10-5S/cm) of PANI-VCMAC system after irradiation may be due to low doping degree (～pH=3)and the difference in morphology as compared with PANI-HCl film.
1997, 15(2): 114-122
Abstract:
The liquid crystalline behavior of anisotropic solutions in 100% sulphuric acid ofaromatic copolyamide obtained by low-temperature solution copolycondensation of tere-phthalic acid chloride (TPC), p-phenylene diamine (PPD) and 4, 4'-diamino-diphenylether(DAPE) has been studied by optical microscopy and X-ray diffeaction. The effects ofinherent viscosity, concentration of copolyamide in sulphuric acid, the content of the thirdmonomer (DAPE) and sequence distribution of copolyamide on the critical concentration,isotropic temperature,phase diagram and texture of liquid crystal were investigated.The schlieren texture was observed and the results of X-ray diffraction indicate that the concentrated solutions of copolyamide exhibit nematic liquid crystalline behavior.
The liquid crystalline behavior of anisotropic solutions in 100% sulphuric acid ofaromatic copolyamide obtained by low-temperature solution copolycondensation of tere-phthalic acid chloride (TPC), p-phenylene diamine (PPD) and 4, 4'-diamino-diphenylether(DAPE) has been studied by optical microscopy and X-ray diffeaction. The effects ofinherent viscosity, concentration of copolyamide in sulphuric acid, the content of the thirdmonomer (DAPE) and sequence distribution of copolyamide on the critical concentration,isotropic temperature,phase diagram and texture of liquid crystal were investigated.The schlieren texture was observed and the results of X-ray diffraction indicate that the concentrated solutions of copolyamide exhibit nematic liquid crystalline behavior.
1997, 15(2): 123-128
Abstract:
The properties and structures of thermotropical liquid crystalline copolyesters basedon p-hydroxybenzoic acid (PHBA), terephthalic acid (TPA) and bisphenol A (BPA) werestudied by DSC, WAXD, hot stage polarized microscopy and NMR. It was found that mostof the copolyesters were soluble in many common organic solvents. The copolyesters hadfow Tm/Tf values and a broad range of liquid crystal phase, making the polymers readilymelt-processable. The effects of annealing at different temperatures on the copolyester containing 33% PHBA were also discussed.It was noted that annealing at ca.200℃ (belowTc-n could lead to the increasing of the crystallinity of the copolyester while the microstructure and sequence structure had not changed.Annealing at ca.280℃ (near Tc-n) could bring a change of crystal and sequence structure and simultaneously made the microdomains be ordered more perfectly.
The properties and structures of thermotropical liquid crystalline copolyesters basedon p-hydroxybenzoic acid (PHBA), terephthalic acid (TPA) and bisphenol A (BPA) werestudied by DSC, WAXD, hot stage polarized microscopy and NMR. It was found that mostof the copolyesters were soluble in many common organic solvents. The copolyesters hadfow Tm/Tf values and a broad range of liquid crystal phase, making the polymers readilymelt-processable. The effects of annealing at different temperatures on the copolyester containing 33% PHBA were also discussed.It was noted that annealing at ca.200℃ (belowTc-n could lead to the increasing of the crystallinity of the copolyester while the microstructure and sequence structure had not changed.Annealing at ca.280℃ (near Tc-n) could bring a change of crystal and sequence structure and simultaneously made the microdomains be ordered more perfectly.
1997, 15(2): 129-138
Abstract:
Poly(phenylene vinylene) (PPV) film was synthesized via a soluble precursor poly-mer. Strong fluorescence at 500-600nm was observed in both precursor and PPV film.Room-temperature conductivity of PPV film doped with FeCl3 depends on the eliminationtemperature, the concentration of FeCl3 and doping time. The maximum conductivity ofdoped PPV at room-temperature can reach about 40 S·cm-1. The temperature depen-dence of conductivity was controlled by 1D-VRH (1 Dimension Variable Range Hopping)model with To value of 3.9×103K.Non-Ohmic conductivity resulting from Schottky effect was observed and the value of converted voltage from Ohmic region into non-Ohmic region at the current-voltage characteristic was found to be dependent upon the work function of electrodes.
Poly(phenylene vinylene) (PPV) film was synthesized via a soluble precursor poly-mer. Strong fluorescence at 500-600nm was observed in both precursor and PPV film.Room-temperature conductivity of PPV film doped with FeCl3 depends on the eliminationtemperature, the concentration of FeCl3 and doping time. The maximum conductivity ofdoped PPV at room-temperature can reach about 40 S·cm-1. The temperature depen-dence of conductivity was controlled by 1D-VRH (1 Dimension Variable Range Hopping)model with To value of 3.9×103K.Non-Ohmic conductivity resulting from Schottky effect was observed and the value of converted voltage from Ohmic region into non-Ohmic region at the current-voltage characteristic was found to be dependent upon the work function of electrodes.
1997, 15(2): 139-145
Abstract:
The disadvantages of Normally White Twisted Nematic Liquid Crystal Display (NW-TN-LCD) were discussed. The reason that the negative birefringent polyimide thin filmswere used to compensate NW-TN-LCD to decrease off-axis leakage, improve contrast ratiosand enlarge viewing angles was explained in this paper. A certain polyimide thin film wastaken as an example to show compensation effect on NW-TN-LCD.
The disadvantages of Normally White Twisted Nematic Liquid Crystal Display (NW-TN-LCD) were discussed. The reason that the negative birefringent polyimide thin filmswere used to compensate NW-TN-LCD to decrease off-axis leakage, improve contrast ratiosand enlarge viewing angles was explained in this paper. A certain polyimide thin film wastaken as an example to show compensation effect on NW-TN-LCD.
1997, 15(2): 146-153
Abstract:
Copolymerization of propylene and hindered piperidine monomers was carried out overa high activity supported Ziegler-Natta catalyst, using Al(C2H5)3 as cocatalyst. Factorswhich affect the copolymerization were studied. The copolymers exhibited high light sta-bility without adding extra light stabilizers. A self-stabilized polypropylene was prepared.
Copolymerization of propylene and hindered piperidine monomers was carried out overa high activity supported Ziegler-Natta catalyst, using Al(C2H5)3 as cocatalyst. Factorswhich affect the copolymerization were studied. The copolymers exhibited high light sta-bility without adding extra light stabilizers. A self-stabilized polypropylene was prepared.
1997, 15(2): 154-161
Abstract:
Crosslinking is one of the effective routes for improving the orientation stability of poledpolymer films. The derivative of polyvinyl alcohol containing 4-nitro-4'-alkoxystilbene andphoto-crosslinkable cinnamyl groups as side chains has been synthesized. The in-situ simul-taneous photo-crosslinking poling of synthesized polymer films has been performed. Thesecond order nonlinear optical coefficient d33 of poled film is 11 pm/V. The SHG mea-surements show that the break-over temperature of SHG signal is raised obviously after irradiation,its orientation stability is doubled as compared with that of non-crosslinking samples.
Crosslinking is one of the effective routes for improving the orientation stability of poledpolymer films. The derivative of polyvinyl alcohol containing 4-nitro-4'-alkoxystilbene andphoto-crosslinkable cinnamyl groups as side chains has been synthesized. The in-situ simul-taneous photo-crosslinking poling of synthesized polymer films has been performed. Thesecond order nonlinear optical coefficient d33 of poled film is 11 pm/V. The SHG mea-surements show that the break-over temperature of SHG signal is raised obviously after irradiation,its orientation stability is doubled as compared with that of non-crosslinking samples.
1997, 15(2): 162-171
Abstract:
An investigation into the organic permselective separation through poly [1-trimethylsilyl-1-propyne] (PTMSP) and (1-trimethylsily1)-1-(1-penta-methyl-disilyl)-1-propyne copoly-mer (TMSP-PMDSP) dense membranes was made to gain an insight into the effect ofthe chemical structure of membrane materials on pervaporation (PV) characteristics. Theresults show that the copolymer has a higher separation factor αorg/water but with a rela-tively lower value of flux Jt (g/m2·h) than pure PTMSP. This phenomenon may be attributed to the introduction of side chain with large bulk volume in copolymer,which brought about a decrease of excess free volume and the improvement of diffusion selectivity to some extent.With the same molar concentration of organic liquids in feed,THF/water solutions have the highest value of αorg/water as well as Jt in comparison with ethanol/water,iso-propanol/water and THF/water mixtures.
An investigation into the organic permselective separation through poly [1-trimethylsilyl-1-propyne] (PTMSP) and (1-trimethylsily1)-1-(1-penta-methyl-disilyl)-1-propyne copoly-mer (TMSP-PMDSP) dense membranes was made to gain an insight into the effect ofthe chemical structure of membrane materials on pervaporation (PV) characteristics. Theresults show that the copolymer has a higher separation factor αorg/water but with a rela-tively lower value of flux Jt (g/m2·h) than pure PTMSP. This phenomenon may be attributed to the introduction of side chain with large bulk volume in copolymer,which brought about a decrease of excess free volume and the improvement of diffusion selectivity to some extent.With the same molar concentration of organic liquids in feed,THF/water solutions have the highest value of αorg/water as well as Jt in comparison with ethanol/water,iso-propanol/water and THF/water mixtures.
1997, 15(2): 172-179
Abstract:
Taking account of the effect of heteroatoms in backbone, this article dealt with themean-square radii of gyration of polyalkyleneoxides by the approach of matrix algebrain accordance with the rotational isomeric state model. Numerical calculation with theparameters available in the literatures indicated that the dependence of on themolecular weight can be expressed by the general formula: = 2>=aMb
Taking account of the effect of heteroatoms in backbone, this article dealt with themean-square radii of gyration of polyalkyleneoxides by the approach of matrix algebrain accordance with the rotational isomeric state model. Numerical calculation with theparameters available in the literatures indicated that the dependence of on themolecular weight can be expressed by the general formula: = 2>=aMb
1997, 15(2): 180-186
Abstract:
A new reactive graft copolymer, poly(tetramthylene glycol) - graft-w-propyl sodiumsulfonate-poly(ethylene glycol) (PTMG-g-PEG-CH2CH2CH2SO3-Na+), was synthesizedby the cationic polymerization of a-w-bifunctional PEG macromonomer (O?CH2—PEG——CH2 CH2 CH2 SO3 Na) and THF. The obtained copolymer exhibits the expected structureas indicated by the result of characterization. Two amino acids (L-arginine, L-tyrosine)were covalently attached to the copolymer after converting the sulfonate group to sulfonyl chloride.So the new reactive graft copolymer(PTMG-g-PEG-CH2CH2SO3-Na+) is expected to be very useful in attachment of potentially bioactive moieties to polymer via a hydrophilic PEG spacer.
A new reactive graft copolymer, poly(tetramthylene glycol) - graft-w-propyl sodiumsulfonate-poly(ethylene glycol) (PTMG-g-PEG-CH2CH2CH2SO3-Na+), was synthesizedby the cationic polymerization of a-w-bifunctional PEG macromonomer (O?CH2—PEG——CH2 CH2 CH2 SO3 Na) and THF. The obtained copolymer exhibits the expected structureas indicated by the result of characterization. Two amino acids (L-arginine, L-tyrosine)were covalently attached to the copolymer after converting the sulfonate group to sulfonyl chloride.So the new reactive graft copolymer(PTMG-g-PEG-CH2CH2SO3-Na+) is expected to be very useful in attachment of potentially bioactive moieties to polymer via a hydrophilic PEG spacer.
1997, 15(2): 187-192
Abstract:
Fluorimetry has been used to characterize ionomers synthesized by copolymerization ofmethyl mehacrylate, methacrylic acid and europium methacrylate (EMA). Under excita-tion of UV light at 375 nm no seif-quenching was found in fluorescence of EMA containingionomers at 615nm within the concentration range of 1.6×10-2 to 11.49×10-2 mol%.This means that the distance between two Eu3+ ions is larger than 5nm. In the sameconcentration range seif-quenching took place in europium octanoate (EOA) containing pply(methyl methacrylate) in which EOA was doped as an additive.
Fluorimetry has been used to characterize ionomers synthesized by copolymerization ofmethyl mehacrylate, methacrylic acid and europium methacrylate (EMA). Under excita-tion of UV light at 375 nm no seif-quenching was found in fluorescence of EMA containingionomers at 615nm within the concentration range of 1.6×10-2 to 11.49×10-2 mol%.This means that the distance between two Eu3+ ions is larger than 5nm. In the sameconcentration range seif-quenching took place in europium octanoate (EOA) containing pply(methyl methacrylate) in which EOA was doped as an additive.
