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2001 Volume 19 Issue 5
2001, 19(5): 441-445
Abstract:
A novel photo-induced initiating system, 2, 2 - dimethoxy-2-phenylacetophenone (DMPA)/ferric tri(N,N-diethyl-dithiocarbamate) [Fe(DC)3], was developed and used for the atom transfer radical polymerization (ATRP) of styrene intoluene. The polymerization proceeds with DMPA as photo-initiator, Fc(DC)3 as catalyst and DC as a reversible transfergroup, while the halogen and ligands are free. Well-defined PSt was prepared and the polymerization mechanism revealed byend group analysis belongs to a reverse ATRP.Block copolymer was prepared by using thus obtained PSt as macroinitiator and Fe(DC)2 as catalyst under UV light irradiation via a conventional ATRP process.
A novel photo-induced initiating system, 2, 2 - dimethoxy-2-phenylacetophenone (DMPA)/ferric tri(N,N-diethyl-dithiocarbamate) [Fe(DC)3], was developed and used for the atom transfer radical polymerization (ATRP) of styrene intoluene. The polymerization proceeds with DMPA as photo-initiator, Fc(DC)3 as catalyst and DC as a reversible transfergroup, while the halogen and ligands are free. Well-defined PSt was prepared and the polymerization mechanism revealed byend group analysis belongs to a reverse ATRP.Block copolymer was prepared by using thus obtained PSt as macroinitiator and Fe(DC)2 as catalyst under UV light irradiation via a conventional ATRP process.
2001, 19(5): 447-449
Abstract:
Conformational elasticity theory recently developed has been used to explore the internal energy contribution tothe elastic force fe/f as a function of strain for poly(cis-1,4-isoprene) and poly(trans-1, 4-isoprene). Calculated fe/f values arein good agreement with those obtained experimentally. Results show that behavior of fe/f is mainly contributed by chemicalstructure, or intramolecular interaction, supporting the experimental observations, and that the internal energy contribution is strain dependent.
Conformational elasticity theory recently developed has been used to explore the internal energy contribution tothe elastic force fe/f as a function of strain for poly(cis-1,4-isoprene) and poly(trans-1, 4-isoprene). Calculated fe/f values arein good agreement with those obtained experimentally. Results show that behavior of fe/f is mainly contributed by chemicalstructure, or intramolecular interaction, supporting the experimental observations, and that the internal energy contribution is strain dependent.
2001, 19(5): 451-454
Abstract:
It had very long been a dream in polymer science to synthesize long multi-block polymer chains with an orderedchain sequence and controllable block lengths. Using ionic or living free radical polymerization or furnishing each end ofpolymer blocks with a reactive functional group, one can only prepare heteropolymer chains with few long blocks, such asdiblock and triblock copolymers. The most plausible result so far was a pentablock copolymer. Recently, using a combinationof polymer physics and synthetic chemistry,we have invented self-assembly assisted polycondensation (SAAP).This communication reports the results of using this novel method to connect 10-100 triblock polymer chains together to form long multi-block heteropolymer chains with an ordered sequence and controllable block lengths.
It had very long been a dream in polymer science to synthesize long multi-block polymer chains with an orderedchain sequence and controllable block lengths. Using ionic or living free radical polymerization or furnishing each end ofpolymer blocks with a reactive functional group, one can only prepare heteropolymer chains with few long blocks, such asdiblock and triblock copolymers. The most plausible result so far was a pentablock copolymer. Recently, using a combinationof polymer physics and synthetic chemistry,we have invented self-assembly assisted polycondensation (SAAP).This communication reports the results of using this novel method to connect 10-100 triblock polymer chains together to form long multi-block heteropolymer chains with an ordered sequence and controllable block lengths.
2001, 19(5): 455-466
Abstract:
A novel transition appeared above thc glass transition temperature of chlorinated polyethylene (CPE) for binaryblends of CPE and additives such as organic small molecules or oligomers. This transition was assigned to the dissociation ofintermolecular hydrogen bonds between the polymer ard additive within the edditive rich phase. Of particular interest is thata novel pyramid crystal was observed in the annealed CPE/hindered phenol blends. Another intriguing observation is thatthese polymer/small molecule blends organized by intermolecular hydrogen bonding have several potential properties,such as shape-memorization,self-restoration,self-adhesiveness and super damping.
A novel transition appeared above thc glass transition temperature of chlorinated polyethylene (CPE) for binaryblends of CPE and additives such as organic small molecules or oligomers. This transition was assigned to the dissociation ofintermolecular hydrogen bonds between the polymer ard additive within the edditive rich phase. Of particular interest is thata novel pyramid crystal was observed in the annealed CPE/hindered phenol blends. Another intriguing observation is thatthese polymer/small molecule blends organized by intermolecular hydrogen bonding have several potential properties,such as shape-memorization,self-restoration,self-adhesiveness and super damping.
2001, 19(5): 467-470
Abstract:
This paper reports a new method to prepare chitosan membrane which could be used as a biomedical material.Addition of a fixation agent composed of alcohol, glycerol and potassium hydroxide can acceletate the sol-gel transformationprocess and hence shorten the prepedion perod. The present method takes about 6 h to get a flexible membrane with fineappearance. The physical and biological properties of the membrane were also investigated and compared with the membraneprepared by conventional method.
This paper reports a new method to prepare chitosan membrane which could be used as a biomedical material.Addition of a fixation agent composed of alcohol, glycerol and potassium hydroxide can acceletate the sol-gel transformationprocess and hence shorten the prepedion perod. The present method takes about 6 h to get a flexible membrane with fineappearance. The physical and biological properties of the membrane were also investigated and compared with the membraneprepared by conventional method.
2001, 19(5): 471-476
Abstract:
The waterborne dispersions of epoxy resin were prepared by the phase inversion emulsification technique.Rheological behavior and its relationship with the structural change of the systems were studied. It was shown that theconcentrated dispersions were highly viscoelatic and pseudoplastic, which was attributed to the formation of a physicalnetwor among tbe waterborne particles via hydrogen bond. The dilutc dispersions were Newtonian fluids. The discrete clusters composed of small waterborne particles were found in diluted dispersions.With increasing solid content,there existed a structural transition via percolation through a cluster-cluster aggregation mode to form the physical network,which was qualitatively evidenced by the TEM morphologies.
The waterborne dispersions of epoxy resin were prepared by the phase inversion emulsification technique.Rheological behavior and its relationship with the structural change of the systems were studied. It was shown that theconcentrated dispersions were highly viscoelatic and pseudoplastic, which was attributed to the formation of a physicalnetwor among tbe waterborne particles via hydrogen bond. The dilutc dispersions were Newtonian fluids. The discrete clusters composed of small waterborne particles were found in diluted dispersions.With increasing solid content,there existed a structural transition via percolation through a cluster-cluster aggregation mode to form the physical network,which was qualitatively evidenced by the TEM morphologies.
2001, 19(5): 477-481
Abstract:
The conformational entropy S and free energy F were calculated by exact enumeration of polysilane chain up to 23segments with excluded volume (EV) and long-range van der Waals (VW) interaction. A nonlinear relation between SEV+VWand chain length n was found though SEV was found to vary linearly with n. We found that the second-order transitiontemperature of polysilane chain with VW interaction increases with the increase of chain length, while that of polysilanechain without VW interaction is chain length independent.Moreover,the free energies FEV+VW are both linearly related with n,and FEV+VW FEV for all temperatures.
The conformational entropy S and free energy F were calculated by exact enumeration of polysilane chain up to 23segments with excluded volume (EV) and long-range van der Waals (VW) interaction. A nonlinear relation between SEV+VWand chain length n was found though SEV was found to vary linearly with n. We found that the second-order transitiontemperature of polysilane chain with VW interaction increases with the increase of chain length, while that of polysilanechain without VW interaction is chain length independent.Moreover,the free energies FEV+VW are both linearly related with n,and FEV+VW FEV for all temperatures.
2001, 19(5): 483-492
Abstract:
The electrochemical copolymerization of aniline and N,N,N'-trimethylthionin (azure B) in aqueous solutions hasbeen carried out using the potential sweep method, The optimum conditions for the coelectrodeposition are that the pH valueand the temperature of the electrolytic solution are controlled at 5.57 and 30℃, respectively, and the scan potential range isset between - 0.25 and 1.10 V (versus SCE). The copolymerization rate of aniline and azure B is about 3 times larger thanthat of aniline in the absence of azure B.The copolymerization of aniline and azure B was verified from the results of visible spectra during electrolysis,FTIR spectra and the atomic force microscopy (AFM) images of the polymers.The in situ visible spectrum for the electrolysis of the solution containing aniline and azure B is different from that of the respective aniline and azure B.The FTIR spectrum of the copolymer is not a superposition of that of polyaniline and poly(azure B).The AFM image of the copolymer is different from those of polyaniline and poly(azure B)and is not a mixture of individual polymers.The conductivity of the copolymer synthesized at pH 5.57 is four orders od magnitude higher than that of polyaniline synthesized under the same conditions,but in the absence of azure B.The electrochemical properties of the copolymer are mainly attributed to polyaniline,but the copolymer has a better electrochemical reversibility and a much faster charge transfer than those of polyaniline.
The electrochemical copolymerization of aniline and N,N,N'-trimethylthionin (azure B) in aqueous solutions hasbeen carried out using the potential sweep method, The optimum conditions for the coelectrodeposition are that the pH valueand the temperature of the electrolytic solution are controlled at 5.57 and 30℃, respectively, and the scan potential range isset between - 0.25 and 1.10 V (versus SCE). The copolymerization rate of aniline and azure B is about 3 times larger thanthat of aniline in the absence of azure B.The copolymerization of aniline and azure B was verified from the results of visible spectra during electrolysis,FTIR spectra and the atomic force microscopy (AFM) images of the polymers.The in situ visible spectrum for the electrolysis of the solution containing aniline and azure B is different from that of the respective aniline and azure B.The FTIR spectrum of the copolymer is not a superposition of that of polyaniline and poly(azure B).The AFM image of the copolymer is different from those of polyaniline and poly(azure B)and is not a mixture of individual polymers.The conductivity of the copolymer synthesized at pH 5.57 is four orders od magnitude higher than that of polyaniline synthesized under the same conditions,but in the absence of azure B.The electrochemical properties of the copolymer are mainly attributed to polyaniline,but the copolymer has a better electrochemical reversibility and a much faster charge transfer than those of polyaniline.
2001, 19(5): 493-498
Abstract:
Two grafting methods, i.e. solution grafting and pre-adsorbing, are introduced to covalently immobilizehydrophilic polymers on segmented polyurethane (SPU) to modify its hydrophilicity and to improve its cell compatibility.Solution grafting results in higher degree of grafting and rougher surface morphology. Cell culture evaluation demonstratesthat the modified membranes thus obtained are disadvantageous to the endothelial cell (ECs) growth probably because thehydrophilic groups on the surface are over-crowded.However,pre-absorbing grafting generates lower degree of grafting,which is detected and confirmed by ATR-FTIR spectra and water contact angle.Scanning electron microscopic (SEM) measurement shows that the latter method produces a plane and smooth morphology,which is similar to the SPU control sample controlled.When grafting with lower monomer concentration,ECs could grow on SPU-g-PHEA [poly(2-hydroxyethyl acrylate)],SPU-g-PAAm(polyacrylamide),SPU-g-PDMA[poly(2-(dimethylamino)ethyl methacrylate)] or quaternized SPU-g-PDMA surface with elongated cell shapes.Hence,the cell compatibility of SPU is improved and a useful method to construct a cell compatible layer on the polymer surface has been developed.
Two grafting methods, i.e. solution grafting and pre-adsorbing, are introduced to covalently immobilizehydrophilic polymers on segmented polyurethane (SPU) to modify its hydrophilicity and to improve its cell compatibility.Solution grafting results in higher degree of grafting and rougher surface morphology. Cell culture evaluation demonstratesthat the modified membranes thus obtained are disadvantageous to the endothelial cell (ECs) growth probably because thehydrophilic groups on the surface are over-crowded.However,pre-absorbing grafting generates lower degree of grafting,which is detected and confirmed by ATR-FTIR spectra and water contact angle.Scanning electron microscopic (SEM) measurement shows that the latter method produces a plane and smooth morphology,which is similar to the SPU control sample controlled.When grafting with lower monomer concentration,ECs could grow on SPU-g-PHEA [poly(2-hydroxyethyl acrylate)],SPU-g-PAAm(polyacrylamide),SPU-g-PDMA[poly(2-(dimethylamino)ethyl methacrylate)] or quaternized SPU-g-PDMA surface with elongated cell shapes.Hence,the cell compatibility of SPU is improved and a useful method to construct a cell compatible layer on the polymer surface has been developed.
2001, 19(5): 499-502
Abstract:
A novel small band-gap conjugated polymer - poly [(3-acetylpyrrole-2, 5-diyl)(4-dimethylaminobenzyliene)(3 -acetylpyrrolequinodimethane-2, 5-diyl)] (PAPDMABE) - and its precursor were synthesized by a simple method andcharacterized by 1H-NMR, FT-IR, TGA and UV-VIS. The polymer can be dissolved in strong polar solvents such as DMSO,DMF or NMP. The band-gap energy of PAPDMABE was found to be 0.95 eV. The conductivity of doped products withiodine falls in the range of a semiconductor.
A novel small band-gap conjugated polymer - poly [(3-acetylpyrrole-2, 5-diyl)(4-dimethylaminobenzyliene)(3 -acetylpyrrolequinodimethane-2, 5-diyl)] (PAPDMABE) - and its precursor were synthesized by a simple method andcharacterized by 1H-NMR, FT-IR, TGA and UV-VIS. The polymer can be dissolved in strong polar solvents such as DMSO,DMF or NMP. The band-gap energy of PAPDMABE was found to be 0.95 eV. The conductivity of doped products withiodine falls in the range of a semiconductor.
2001, 19(5): 503-507
Abstract:
Supported An catalysts for low-temperature CO oxidation were prepared by solvated motal atom impregnation(SMAI) and conventional impregnation (CI). X-ray photoelectron spectroscopy (XPS) investigations indicated that theelemental gold in all the samples was in the metallic state. XRD measurements showed that the mean diameters of Auparticles prepared by SMAI were smaller than those prepared by CI with the same gold content. Catalytic tests showed thatthe SMAI catalyst had higher CO oxidation activity than the CI catalyst with the same compositions.Both SMAI and CI catalysts exhibited high activity in low temperature CO oxidation.Full CO conversion was obtained at 323-383K.
Supported An catalysts for low-temperature CO oxidation were prepared by solvated motal atom impregnation(SMAI) and conventional impregnation (CI). X-ray photoelectron spectroscopy (XPS) investigations indicated that theelemental gold in all the samples was in the metallic state. XRD measurements showed that the mean diameters of Auparticles prepared by SMAI were smaller than those prepared by CI with the same gold content. Catalytic tests showed thatthe SMAI catalyst had higher CO oxidation activity than the CI catalyst with the same compositions.Both SMAI and CI catalysts exhibited high activity in low temperature CO oxidation.Full CO conversion was obtained at 323-383K.
2001, 19(5): 509-516
Abstract:
A substituted glycolide, 3-bencyloxymethyl-1, 4-dioxane-2, 5-dione, was synthesized. It is a suitable precursor forthe preparation of a new hydrophilic biodegradable poly(α-hydroxy acid). The polymerizations were carried out in bulk inthe presence of Sn(Oct)2 at 120-140℃. The resulting polymers were subjected to hydrogenolysis with a Pd/C catalyst in amixed solvent to remove the protecting benzyl groups. A novel poly(α-hydroxy acid) with pendant hydroxy groups wasobtained. The hydrophilicity of the resulting polymer was evaluated preliminarily.
A substituted glycolide, 3-bencyloxymethyl-1, 4-dioxane-2, 5-dione, was synthesized. It is a suitable precursor forthe preparation of a new hydrophilic biodegradable poly(α-hydroxy acid). The polymerizations were carried out in bulk inthe presence of Sn(Oct)2 at 120-140℃. The resulting polymers were subjected to hydrogenolysis with a Pd/C catalyst in amixed solvent to remove the protecting benzyl groups. A novel poly(α-hydroxy acid) with pendant hydroxy groups wasobtained. The hydrophilicity of the resulting polymer was evaluated preliminarily.
2001, 19(5): 517-520
Abstract:
Hyperbranched aromatic polpmers were prepared by Friedel-Crafts reaction with Lewis acid, AlCl3 and ZnCl3, asthe catalysts. In this work, hyperbranched polybenzyl (PB) and poly(methylene) naphthalene(PN) were synthesized andcharacterized by 1H-NMR and GPc. In addition, their florescence properties were measured with steady-state florescencespectra in THF and ethylene dichloride. The quantum yields of polybenzyl and poly(methylene)naphthalene in ethylenedichloride are much larger than those in THF.
Hyperbranched aromatic polpmers were prepared by Friedel-Crafts reaction with Lewis acid, AlCl3 and ZnCl3, asthe catalysts. In this work, hyperbranched polybenzyl (PB) and poly(methylene) naphthalene(PN) were synthesized andcharacterized by 1H-NMR and GPc. In addition, their florescence properties were measured with steady-state florescencespectra in THF and ethylene dichloride. The quantum yields of polybenzyl and poly(methylene)naphthalene in ethylenedichloride are much larger than those in THF.
2001, 19(5): 521-526
Abstract:
The 1,1'-binaphthol based oligomers 3 and 7 with 3, 3'-acetylene-phenylene-acetylene spacer were prepared fromBINOL 1. The high optical rotation value and CD spectra demonstrated the main chain chirality of the oligomer molecule.The UV-VIS and fluorescent spectra evidence the characteristics of conjugated structure. In comparison with oligomer 2bearing 3,3'-acetylene spacer, the oligomers 3 and 7 have longer efficient conjugation segment, and their fluorescent quantumyields (φ) increased (0.60-0.65 versus 0.14).Extending the effective conjugation segment would improve the photophysical properties of chiral conjugated polymers.
The 1,1'-binaphthol based oligomers 3 and 7 with 3, 3'-acetylene-phenylene-acetylene spacer were prepared fromBINOL 1. The high optical rotation value and CD spectra demonstrated the main chain chirality of the oligomer molecule.The UV-VIS and fluorescent spectra evidence the characteristics of conjugated structure. In comparison with oligomer 2bearing 3,3'-acetylene spacer, the oligomers 3 and 7 have longer efficient conjugation segment, and their fluorescent quantumyields (φ) increased (0.60-0.65 versus 0.14).Extending the effective conjugation segment would improve the photophysical properties of chiral conjugated polymers.
2001, 19(5): 527-529
Abstract:
A better understanding of a recently raised argument on whether there occurs a structure change during yieldinghas been acquired by using molecular simulation. That is, when monitoring the displacements of all atoms before and afterthe yield, a structure transition does occur, which is the "atomic jump" that coordinates the amount of the atoms in thepolymer and makes a large step beyond～0.05 nm for all those atoms. Results indicate that the complex of polymer chain packing induces the multiple atomic jumps around the yield point.This explains why polymers have a broader yielding peak.
A better understanding of a recently raised argument on whether there occurs a structure change during yieldinghas been acquired by using molecular simulation. That is, when monitoring the displacements of all atoms before and afterthe yield, a structure transition does occur, which is the "atomic jump" that coordinates the amount of the atoms in thepolymer and makes a large step beyond～0.05 nm for all those atoms. Results indicate that the complex of polymer chain packing induces the multiple atomic jumps around the yield point.This explains why polymers have a broader yielding peak.
