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1996 Volume 14 Issue 1
1996, 14(1): 1-18
Abstract:
Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to establish the multiplicity of dielectric relaxationtransitions which reflects the small- and large-scale types of molecular motion. It was shownthat dielectric relaxation processes occurring in accordance with local mechanism (relaxationtimes 10-9--10-7s. and the activation energy 10--50kJ/mol)are due to the mobility of kinetic chain elements of different length within a monomer units.It was found that the dielectric relaxation process connected with a large-scale form of molecular motion(relaxation times10-5—10-6s.and the activation energy 100kj/mol) did not depend on the molecular mass but was influenced by factors changing the conformational state of the macromolecule ,It is established that the cooperative reorientation mobility of associated mesogenic fragments is the source of the large-scale process.
Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to establish the multiplicity of dielectric relaxationtransitions which reflects the small- and large-scale types of molecular motion. It was shownthat dielectric relaxation processes occurring in accordance with local mechanism (relaxationtimes 10-9--10-7s. and the activation energy 10--50kJ/mol)are due to the mobility of kinetic chain elements of different length within a monomer units.It was found that the dielectric relaxation process connected with a large-scale form of molecular motion(relaxation times10-5—10-6s.and the activation energy 100kj/mol) did not depend on the molecular mass but was influenced by factors changing the conformational state of the macromolecule ,It is established that the cooperative reorientation mobility of associated mesogenic fragments is the source of the large-scale process.
1996, 14(1): 19-25
Abstract:
Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place over the entire temperature range between its meltingpoint and clearing point and the orientation level is strongly temperature-dependent, thedevelopment with time of the magnetic orieatation follows an exponeotial-type relation,and the smectic phase state influences the thermal relaxation process in the absence of the magnetic field.
Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place over the entire temperature range between its meltingpoint and clearing point and the orientation level is strongly temperature-dependent, thedevelopment with time of the magnetic orieatation follows an exponeotial-type relation,and the smectic phase state influences the thermal relaxation process in the absence of the magnetic field.
1996, 14(1): 26-33
Abstract:
A new kind of inorganic polymer, viz. silica-supported polytitazane (Ti-N), and itsplatinum complex (Ti-N-Pt) were prepared. Cyclohexanone can be obtained in a maximumyield of about 62.2% in the hydrogenation of phenol over Ti-N-Pt at room temperatureunder atmospheric pressure. The effects of mole ratio of N/Pt in the complex, concentrationof the catalyst and reaction temperature on the catalytic activity and selectivity have beenstudied. The complex can be reused several times without loss in its catalytic activity.
A new kind of inorganic polymer, viz. silica-supported polytitazane (Ti-N), and itsplatinum complex (Ti-N-Pt) were prepared. Cyclohexanone can be obtained in a maximumyield of about 62.2% in the hydrogenation of phenol over Ti-N-Pt at room temperatureunder atmospheric pressure. The effects of mole ratio of N/Pt in the complex, concentrationof the catalyst and reaction temperature on the catalytic activity and selectivity have beenstudied. The complex can be reused several times without loss in its catalytic activity.
1996, 14(1): 34-40
Abstract:
This paper mainly deals with the design and synthesis of a novel styrene-butadieneblock copolymer. When this copolymer is used in the tread portion of tyres, it can improvewet skid resistance and reduce rolling resistance without sacrificing its general physical-mechanical properties. The visco-elastic curve of tire tread using the novel copolymer asits rubber portion was showed. Reactivity ratios for two monomers in the polymerizingsystem were calculated. The diagrams of differelitial, integral and finite difference calculi thronghout the whole melecular chain were presented.The influence of the micro- and macro-structure of the copolymer chain on wet skid resistance and rolling resistance was discussed.
This paper mainly deals with the design and synthesis of a novel styrene-butadieneblock copolymer. When this copolymer is used in the tread portion of tyres, it can improvewet skid resistance and reduce rolling resistance without sacrificing its general physical-mechanical properties. The visco-elastic curve of tire tread using the novel copolymer asits rubber portion was showed. Reactivity ratios for two monomers in the polymerizingsystem were calculated. The diagrams of differelitial, integral and finite difference calculi thronghout the whole melecular chain were presented.The influence of the micro- and macro-structure of the copolymer chain on wet skid resistance and rolling resistance was discussed.
1996, 14(1): 41-47
Abstract:
The ladderlike structure of PPSQ synthesized by using four kinds of catalysts (MgF2,LiF, KOH and DCC) at different polymerization conditions has been investigated by IRand NMR. In the system using MgF2 as the main catalyst, the most important factorwhich affects the ladderlike structure of PPSQ is the composition of the dual catalysts,MgF2 and DCC. PPSQ prepared by using KOH as the catalyst has the highest regularityof ladderlike structure among all samples. PPSQ with different degree of ladder regularity can be obtained by choice of polymerization conditions.
The ladderlike structure of PPSQ synthesized by using four kinds of catalysts (MgF2,LiF, KOH and DCC) at different polymerization conditions has been investigated by IRand NMR. In the system using MgF2 as the main catalyst, the most important factorwhich affects the ladderlike structure of PPSQ is the composition of the dual catalysts,MgF2 and DCC. PPSQ prepared by using KOH as the catalyst has the highest regularityof ladderlike structure among all samples. PPSQ with different degree of ladder regularity can be obtained by choice of polymerization conditions.
1996, 14(1): 48-56
Abstract:
A super-absorbent polymer is prepared by graft polymerizing acrylamide (AM) ontopotato starch using ceric ammonium nitrate (CAN) and N, N′-methylene-bis-acrylamide(bisAM) as an initiator and cross-linking agent respectively, and then subjecting the potatostarch-poly(acrylamide) (PAM) graft copolymer (SPAM ) to alkaline saponification. Thewater absorbency (WA) of the sample is nearly 5000 g H2O/g for dry sample in 24 hat room temperature and is far larger than that of reported in the literature[1]. The variables affecting the WA were investigated and optimized,they were:concentrations of potato starch,AM,CAN and bisAM were 26.3g/L,1.14 mol/L,10.3 mmol/L and 0.53 mmol/L,respectively.The amount of sodium hydroxide was 15 g and the temperatures of graft copolymerization and saponification reactions were 60℃ and 95℃.The time of graft copolymerization and saponification reactions was 2 h,respectively.
A super-absorbent polymer is prepared by graft polymerizing acrylamide (AM) ontopotato starch using ceric ammonium nitrate (CAN) and N, N′-methylene-bis-acrylamide(bisAM) as an initiator and cross-linking agent respectively, and then subjecting the potatostarch-poly(acrylamide) (PAM) graft copolymer (SPAM ) to alkaline saponification. Thewater absorbency (WA) of the sample is nearly 5000 g H2O/g for dry sample in 24 hat room temperature and is far larger than that of reported in the literature[1]. The variables affecting the WA were investigated and optimized,they were:concentrations of potato starch,AM,CAN and bisAM were 26.3g/L,1.14 mol/L,10.3 mmol/L and 0.53 mmol/L,respectively.The amount of sodium hydroxide was 15 g and the temperatures of graft copolymerization and saponification reactions were 60℃ and 95℃.The time of graft copolymerization and saponification reactions was 2 h,respectively.
1996, 14(1): 57-62
Abstract:
A natural polymer catalyst, sillca-supported chitosan palladium complex (abbr. asSiO2-CS-Pd) was found to catalyze the hydrogenation of phenol and cresols to correspond-ing cyclohexanones in high yield and 100% selectivity at 70℃ and 1.01325×105 Pa mildconditions. N/Pd molar ratio in the complex, temperature and solvents have much infiuenceon the reaction. The reactivity order of reactants was found to be: phenol >m->p->o-cresol. The catalyst is stable during the reaction and could be repeatedly used for several times without much decrease in its catalytic activity.
A natural polymer catalyst, sillca-supported chitosan palladium complex (abbr. asSiO2-CS-Pd) was found to catalyze the hydrogenation of phenol and cresols to correspond-ing cyclohexanones in high yield and 100% selectivity at 70℃ and 1.01325×105 Pa mildconditions. N/Pd molar ratio in the complex, temperature and solvents have much infiuenceon the reaction. The reactivity order of reactants was found to be: phenol >m->p->o-cresol. The catalyst is stable during the reaction and could be repeatedly used for several times without much decrease in its catalytic activity.
1996, 14(1): 63-70
Abstract:
The sol/gel phase diagrams were studied for two systems: polyacrylamide/Cr (III) andpolyacrylamide/glyoxal. Sol or gel phase could be distinguished according to the concen-trations of polymer and crosslinker. The boundary polymer concentration did not de-pend on the types of gelation and decreased with increasing polymer dimension (molecularweight and conformation). The gelation, which is basically interchain bonding, requires theoccurrence of entanglement. The overlap concentration is thus considered as the minimum polymer concentration required for gelation.
The sol/gel phase diagrams were studied for two systems: polyacrylamide/Cr (III) andpolyacrylamide/glyoxal. Sol or gel phase could be distinguished according to the concen-trations of polymer and crosslinker. The boundary polymer concentration did not de-pend on the types of gelation and decreased with increasing polymer dimension (molecularweight and conformation). The gelation, which is basically interchain bonding, requires theoccurrence of entanglement. The overlap concentration is thus considered as the minimum polymer concentration required for gelation.
1996, 14(1): 71-79
Abstract:
Two series of new liquid crystailine polymers with T-shaped two-dimensional mesogenicunits were synthesized by low temperature solution polycondensations of 4-substituted N-2, 5- dihydroxybenzylidene aniline monomers with different diacyl dichlorides. The polymerswere found to be nematic and shown liquid crystailine behavior. The melting temperatureT_m and the clearing temperature Ti of the polymers change regularly with varying of themonomer structures.
Two series of new liquid crystailine polymers with T-shaped two-dimensional mesogenicunits were synthesized by low temperature solution polycondensations of 4-substituted N-2, 5- dihydroxybenzylidene aniline monomers with different diacyl dichlorides. The polymerswere found to be nematic and shown liquid crystailine behavior. The melting temperatureT_m and the clearing temperature Ti of the polymers change regularly with varying of themonomer structures.
1996, 14(1): 80-85
Abstract:
The fully oxidized state of polyaniline (PANI), pernigraniline (PN), was synthesizedby oxidation of the emeraldine base form of PANI dissolved in NMP solvent with m-chloroperoxybenzoic acid. The resulted PN was characterized by FTIR and UV-Visiblespectra. The third-order nonlinear optical properties of PN in concentrated sulfuric acid(PN/H2SO4) were measured by a degenerated four wave mixing (DFWM) method. The re-sults obtained suggest that the soliton-pair intermediate state associated with the degenerated state does not play a major role in the third order nonlinear optical properties of PANI.
The fully oxidized state of polyaniline (PANI), pernigraniline (PN), was synthesizedby oxidation of the emeraldine base form of PANI dissolved in NMP solvent with m-chloroperoxybenzoic acid. The resulted PN was characterized by FTIR and UV-Visiblespectra. The third-order nonlinear optical properties of PN in concentrated sulfuric acid(PN/H2SO4) were measured by a degenerated four wave mixing (DFWM) method. The re-sults obtained suggest that the soliton-pair intermediate state associated with the degenerated state does not play a major role in the third order nonlinear optical properties of PANI.
1996, 14(1): 86-90
Abstract:
The kinetics of mesophase formation of a thermotropic hydroxyethyl cellulose acetatefrom isotropic phase to cholesteric mesophase has been studied by means of depolariz-ing transmittance method. Avrami type analysis of the data gives an exponent n close to1, which suggests the nucleation followed by rod-like growth. It means that the kineticbehavior of phase transition from isotropic to cholesteric mesophase is very similar to thatof the mesophase formation from isotropic to nematic mesophase.
The kinetics of mesophase formation of a thermotropic hydroxyethyl cellulose acetatefrom isotropic phase to cholesteric mesophase has been studied by means of depolariz-ing transmittance method. Avrami type analysis of the data gives an exponent n close to1, which suggests the nucleation followed by rod-like growth. It means that the kineticbehavior of phase transition from isotropic to cholesteric mesophase is very similar to thatof the mesophase formation from isotropic to nematic mesophase.
1996, 14(1): 91-96
Abstract:
The cationic polymerizations of 1, 3-pentadiene were initiated by AlCl3 in n-hexaneat 30℃ in the presence of alkyl halides, i.e., tert-butyl chloride, tert-butyl bromide andisobutyl chloride. The effects of these halides on the polymer yield, molecular weight,crosslinking reaction, cyclization and polymer microstructure, have been investigated. Twomain side reactions, crosslinking and cyclization, were suppressed and reduced by theaddition of the halides. The proportion of 1, 4 units of polymer chains was increased by the presence of the halides,which reduced the polymer yield and the molecular weight of polymers.
The cationic polymerizations of 1, 3-pentadiene were initiated by AlCl3 in n-hexaneat 30℃ in the presence of alkyl halides, i.e., tert-butyl chloride, tert-butyl bromide andisobutyl chloride. The effects of these halides on the polymer yield, molecular weight,crosslinking reaction, cyclization and polymer microstructure, have been investigated. Twomain side reactions, crosslinking and cyclization, were suppressed and reduced by theaddition of the halides. The proportion of 1, 4 units of polymer chains was increased by the presence of the halides,which reduced the polymer yield and the molecular weight of polymers.
