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2003 Volume 21 Issue 1
2003, 21(1): 1-4
Abstract:
Stable and well-dispersed poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium colloidal clusters wereprepaxed via the reduction of ruthenium(III) chloride by refluxing with low boiling point alcohols. Investigation of the size ofRu colloids by transmission electron microscopy (TEM) indicated that the average diametes could be controlled in the rangeof 1.2-1.6 nm with relative standard deviations of less than 0.33 by changing the molar ratio of PVP to Ru. The X-ray photoelectron spectroscopy(XPS) characterization verified the formation of elemental ruthenium colloids.
Stable and well-dispersed poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium colloidal clusters wereprepaxed via the reduction of ruthenium(III) chloride by refluxing with low boiling point alcohols. Investigation of the size ofRu colloids by transmission electron microscopy (TEM) indicated that the average diametes could be controlled in the rangeof 1.2-1.6 nm with relative standard deviations of less than 0.33 by changing the molar ratio of PVP to Ru. The X-ray photoelectron spectroscopy(XPS) characterization verified the formation of elemental ruthenium colloids.
2003, 21(1): 5-8
Abstract:
Porcine pancreas lipase (PPL) and PPL immobilized on narrow distributed micron-sized glass beads wereemployed successfully for the ring-opening polymerization of 5, 5-dimethyl-1, 3-dioxan-2-one (DTC) for the first time.Different polymerization conditions such as enzyme concentration and reaction temperature were studied. Immobilized PPLexhibits higher activity than native PPL. Along wth the increasing enzyme concentration, the molecular weigh of resultingPDTC decreases. PPL immobilized on narrow distributed micron-sized glass beads has outstanding recyclability.For the third recycle time,immobilized PPL exhibits the highest catalytic activity and with high activity even after the fifth recyle time for the synthesis of PDTC.The 1H-NMR spectra indicate that decarboxylation does not occur during the ring-opening polymerization.
Porcine pancreas lipase (PPL) and PPL immobilized on narrow distributed micron-sized glass beads wereemployed successfully for the ring-opening polymerization of 5, 5-dimethyl-1, 3-dioxan-2-one (DTC) for the first time.Different polymerization conditions such as enzyme concentration and reaction temperature were studied. Immobilized PPLexhibits higher activity than native PPL. Along wth the increasing enzyme concentration, the molecular weigh of resultingPDTC decreases. PPL immobilized on narrow distributed micron-sized glass beads has outstanding recyclability.For the third recycle time,immobilized PPL exhibits the highest catalytic activity and with high activity even after the fifth recyle time for the synthesis of PDTC.The 1H-NMR spectra indicate that decarboxylation does not occur during the ring-opening polymerization.
2003, 21(1): 9-14
Abstract:
A series of newly designed monomers of 2-vinylterephthalates (VT) were synthesized. The monomers contain onephenylene group connected with two alkyl groups (carbon number varying from 1 to 6) via ester linkage. Their chemicalstructures were confirmed by mass spectroscopy (MS), ~1-H-NMR, and elemental analysis (EA). The corresponding polymers,poly[di(alkyl) vinylterephthalate]s (PDAVTs), were obtained using convenional free redical polymerization. The polymers were found to be able to develop into liquid crystalline phase when the size of the alkyl group in the side-chain increases to be larger than the ethyl group.
A series of newly designed monomers of 2-vinylterephthalates (VT) were synthesized. The monomers contain onephenylene group connected with two alkyl groups (carbon number varying from 1 to 6) via ester linkage. Their chemicalstructures were confirmed by mass spectroscopy (MS), ~1-H-NMR, and elemental analysis (EA). The corresponding polymers,poly[di(alkyl) vinylterephthalate]s (PDAVTs), were obtained using convenional free redical polymerization. The polymers were found to be able to develop into liquid crystalline phase when the size of the alkyl group in the side-chain increases to be larger than the ethyl group.
2003, 21(1): 15-19
Abstract:
The intermolecular interaction between poly(methyl methacrylate) (PMMA) and polystyrene (PS) intetrahydrofuran (THF) and N,N'-dimethyl formamide (DMF) solvents was studied at 28℃ using a dilute solution viscometrymethod. Solvent is believed to play a key role in characterizing the viscosity behavior of the polymer solution. The intrinsicviscosity and viscosity interaction parameter were experimentally measured for the binary (solvent/polymer) and for theternary systems in two solvents. The compatibility of the polymer mixture was discussed in terms of the sign of △bsub>m.The results show that the compatibility of PMMA/PS blend in DMF is larger than that in THF.
The intermolecular interaction between poly(methyl methacrylate) (PMMA) and polystyrene (PS) intetrahydrofuran (THF) and N,N'-dimethyl formamide (DMF) solvents was studied at 28℃ using a dilute solution viscometrymethod. Solvent is believed to play a key role in characterizing the viscosity behavior of the polymer solution. The intrinsicviscosity and viscosity interaction parameter were experimentally measured for the binary (solvent/polymer) and for theternary systems in two solvents. The compatibility of the polymer mixture was discussed in terms of the sign of △bsub>m.The results show that the compatibility of PMMA/PS blend in DMF is larger than that in THF.
2003, 21(1): 21-27
Abstract:
The synthesis and characterization of a new series of liquid crystalline polymers, poly(dicycloalkylvinylterephthalate)s, are reported. The basic building blocks of these polymers are not mesogenic by themselves. However,very stable mesophases can be generated by self-assembly of the polymer molecules. This approach suggests a novel designstrategy of liquid crystalline polymers with flexible and apolar building blocks.
The synthesis and characterization of a new series of liquid crystalline polymers, poly(dicycloalkylvinylterephthalate)s, are reported. The basic building blocks of these polymers are not mesogenic by themselves. However,very stable mesophases can be generated by self-assembly of the polymer molecules. This approach suggests a novel designstrategy of liquid crystalline polymers with flexible and apolar building blocks.
2003, 21(1): 29-33
Abstract:
The complexes of poly(methacrylic acid-co-methyl methacrylate) network with poly(ethylene glycol) stabilized byhydrogen bonds were prepared. By introducing the poly(ethylene glycol), a large difference in storage modulus below andabove the glass transition temperature occurred and the complexes exhibited shape memory behaviors. The morphology ofcomplexes was studied by using DSC, WAXD, and DMA. The results indicate that the fixed phase of this kind of novel shape memory materials is the amorphous state of PEG:PMAA complex phase.The shape recoverability almost reaches 100%.This type of complexes can be regarded as a novel shape memory network.
The complexes of poly(methacrylic acid-co-methyl methacrylate) network with poly(ethylene glycol) stabilized byhydrogen bonds were prepared. By introducing the poly(ethylene glycol), a large difference in storage modulus below andabove the glass transition temperature occurred and the complexes exhibited shape memory behaviors. The morphology ofcomplexes was studied by using DSC, WAXD, and DMA. The results indicate that the fixed phase of this kind of novel shape memory materials is the amorphous state of PEG:PMAA complex phase.The shape recoverability almost reaches 100%.This type of complexes can be regarded as a novel shape memory network.
2003, 21(1): 35-43
Abstract:
A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation of polymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simple shear flow,extensional flow,vortical flow,and mixed flow respectively.
A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation of polymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simple shear flow,extensional flow,vortical flow,and mixed flow respectively.
2003, 21(1): 45-50
Abstract:
A new phosphorylcholine, (6-hydroxy) hexyl-2-(trimethylammonio) ethyl phosphate (HTEP), was synthesized andcharasterized. Segmented polyurethane (SPU) containing phosphorylcholine structure was synthesized based ondiphenylmethane diisocyanate (MDI), soft segment polytetramethylene glycol (PTMG) and HTEP, with 1,4-butanediol (BD)as a chain extender. The existence of phosphorylcholine structure on the surface of SPU was revealed by attenuated totalreflectance Fourier transform infrard spectroscopy(ATR-FTIR),X-ray photoelectron spectroscopy(XPS) and water contact angle measurements.The blood compatibilities of the polymers were evaluated by hemolytic testing and a platelet-rich plasma(PRP) adhesion experiment,which was viewed by scanning electron microscopy (SEM) with polyurethane as a reference.The novel segmented polyurethane containing phosphorylcholine structure showed improved blood compatibility.
A new phosphorylcholine, (6-hydroxy) hexyl-2-(trimethylammonio) ethyl phosphate (HTEP), was synthesized andcharasterized. Segmented polyurethane (SPU) containing phosphorylcholine structure was synthesized based ondiphenylmethane diisocyanate (MDI), soft segment polytetramethylene glycol (PTMG) and HTEP, with 1,4-butanediol (BD)as a chain extender. The existence of phosphorylcholine structure on the surface of SPU was revealed by attenuated totalreflectance Fourier transform infrard spectroscopy(ATR-FTIR),X-ray photoelectron spectroscopy(XPS) and water contact angle measurements.The blood compatibilities of the polymers were evaluated by hemolytic testing and a platelet-rich plasma(PRP) adhesion experiment,which was viewed by scanning electron microscopy (SEM) with polyurethane as a reference.The novel segmented polyurethane containing phosphorylcholine structure showed improved blood compatibility.
2003, 21(1): 51-56
Abstract:
The grafting of ethylene glycol dimethacrylate (EGDMA) onto silk in aqueous alcohol systems using potassiumpersulfate (KPS) in the presence of air was investigated. Effects of grafting conditions, such as concentrations of monomer,initiator and formic acid, temperature and time, on the graft yield were determined. The optimum graft conditions were foundto be: T = 80℃, t = 30 min, [KPS] = 1.85% [on the weight ofmonomer (owm)]; [formic acid] = 0.2% (V/V); [EGDMA] =80% [on the weight of fiber(owf)].The activation energy of grafting at 50-80℃ was found to be 71.31 kJ/mol for EGDMA.Grafting equations were also evaluated.The graft yield value can be regulated by the concentration of monomer.The graft copolymerization of EFDMA onto silk is effective in improving the crease-proofing of silk fabrics.
The grafting of ethylene glycol dimethacrylate (EGDMA) onto silk in aqueous alcohol systems using potassiumpersulfate (KPS) in the presence of air was investigated. Effects of grafting conditions, such as concentrations of monomer,initiator and formic acid, temperature and time, on the graft yield were determined. The optimum graft conditions were foundto be: T = 80℃, t = 30 min, [KPS] = 1.85% [on the weight ofmonomer (owm)]; [formic acid] = 0.2% (V/V); [EGDMA] =80% [on the weight of fiber(owf)].The activation energy of grafting at 50-80℃ was found to be 71.31 kJ/mol for EGDMA.Grafting equations were also evaluated.The graft yield value can be regulated by the concentration of monomer.The graft copolymerization of EFDMA onto silk is effective in improving the crease-proofing of silk fabrics.
2003, 21(1): 57-64
Abstract:
The copolymerization of styrene (St) and acrylonitrile (AN) complexed with CuCl2 monomer by a free radicalmechanism was performed using benzoyl peroxide as an initiator at 65℃ under N2 atmosphere for 150 min. The rate ofpolymerization (Rp) was found to increase linearly with the concentration (in mol/L) of CuCl2, AN and St through scalingrelations. The activation energy of the copolymerization process in the presence and absence of CuCl2 was found to be 46.5 kJ/mol and 102 kJ/mol,respectively.The viscosity average molecular weight of the copolymer and the kp2/kt ratio were determired to further assess the accelerating effect of CuCl2 on the copolymerization process.The copolymerization process in the presence of CuCl2 has a radical complex mechanism.
The copolymerization of styrene (St) and acrylonitrile (AN) complexed with CuCl2 monomer by a free radicalmechanism was performed using benzoyl peroxide as an initiator at 65℃ under N2 atmosphere for 150 min. The rate ofpolymerization (Rp) was found to increase linearly with the concentration (in mol/L) of CuCl2, AN and St through scalingrelations. The activation energy of the copolymerization process in the presence and absence of CuCl2 was found to be 46.5 kJ/mol and 102 kJ/mol,respectively.The viscosity average molecular weight of the copolymer and the kp2/kt ratio were determired to further assess the accelerating effect of CuCl2 on the copolymerization process.The copolymerization process in the presence of CuCl2 has a radical complex mechanism.
2003, 21(1): 65-70
Abstract:
The correlation between shape and size of linear chains on the simple cubic lattice is investigated using a dynamicMonte Carlo technique. A positive correlation between the asphericity parameter A and the square of the end-to-end distanceR2, as well as that between A and the square of the radius of gyration S2, is found for both RW and SAW chains, indicatingthat a chain conformation of small size is usually more spherical than one of large size. The result can explain why the shape of the SAW chain deviate much more from a sphere than that of the RW chain,and can also explain the similar dependence of size and shape on chain stiffness and on the distance of the first bead of a chain from an infinitely large flat surface.
The correlation between shape and size of linear chains on the simple cubic lattice is investigated using a dynamicMonte Carlo technique. A positive correlation between the asphericity parameter A and the square of the end-to-end distanceR2, as well as that between A and the square of the radius of gyration S2, is found for both RW and SAW chains, indicatingthat a chain conformation of small size is usually more spherical than one of large size. The result can explain why the shape of the SAW chain deviate much more from a sphere than that of the RW chain,and can also explain the similar dependence of size and shape on chain stiffness and on the distance of the first bead of a chain from an infinitely large flat surface.
2003, 21(1): 71-75
Abstract:
A high-quality polyene can be obtained by exensive dehydrochlorination of poly(vinyl chloride) (PVC) in aliquid/solid two-phase system. The liquid phase is a tetrahydrofuran solution of PVC containing a small amount ofpoly(ethylene glycol) with molar mass of 400 g as a phase transfer catalys. The solid phase is potassium hydroxide particles.The structure of the polyene is polyacetylene-like and has a long conjugated C=C sequence and a narrow dispersity of polyene sequences according to its FT-infrared and Raman spectra.The environmental stability of the polyene was also studied by IR,Raman spectra and elemental analysis.Experimetal results demonstrated that the polyene was susceptible to air and could be changed into a material containing high concentrations of hydroxyl and carbonyl groups.The polyene sequences were shortened and its dispersity became broader due to the effect of dioxygen.
A high-quality polyene can be obtained by exensive dehydrochlorination of poly(vinyl chloride) (PVC) in aliquid/solid two-phase system. The liquid phase is a tetrahydrofuran solution of PVC containing a small amount ofpoly(ethylene glycol) with molar mass of 400 g as a phase transfer catalys. The solid phase is potassium hydroxide particles.The structure of the polyene is polyacetylene-like and has a long conjugated C=C sequence and a narrow dispersity of polyene sequences according to its FT-infrared and Raman spectra.The environmental stability of the polyene was also studied by IR,Raman spectra and elemental analysis.Experimetal results demonstrated that the polyene was susceptible to air and could be changed into a material containing high concentrations of hydroxyl and carbonyl groups.The polyene sequences were shortened and its dispersity became broader due to the effect of dioxygen.
2003, 21(1): 77-85
Abstract:
The formation mechanism of monodisperse polymer latex particles in the emulsifier-free emulsion polymerizationof methyl methacrylate and butyl acrylate with potassium persulfate as initiator was investigated. A multi-step formationmechanism for the monodisperse polymer particles was proposed. The nucleation mechanism is considered to be the coagulation of the precursor particles by homogeneous nucleation when the primary particles reach a critical size with high surface charge density and sufficient stability.It had been proved by a special experiment that the early latex particles formed by the coagulation were stable.The primary particles grow by absorbing monomers and radicals in the polymerization system and then become colloidally unstable again due to the understandable decrease of particle surface charge density,which leads to the affregation of the growing particles and the formation of larger latex particles therefrom.After the nucleation period,the preferential aggregation of the smaller particles in the propagation process leads to the change of the particles towards a uniform size and narrower particle size distribution.The coexistence and competition of homogeneous nucleation,coagulation,propagation and aggregation result in the increase of the polydispersity index(U=D43/D10) in the first stage,then its decrease in the later stage because of the competition of propagation and aggregation,and the gradual formation of the monodisperse particles.
The formation mechanism of monodisperse polymer latex particles in the emulsifier-free emulsion polymerizationof methyl methacrylate and butyl acrylate with potassium persulfate as initiator was investigated. A multi-step formationmechanism for the monodisperse polymer particles was proposed. The nucleation mechanism is considered to be the coagulation of the precursor particles by homogeneous nucleation when the primary particles reach a critical size with high surface charge density and sufficient stability.It had been proved by a special experiment that the early latex particles formed by the coagulation were stable.The primary particles grow by absorbing monomers and radicals in the polymerization system and then become colloidally unstable again due to the understandable decrease of particle surface charge density,which leads to the affregation of the growing particles and the formation of larger latex particles therefrom.After the nucleation period,the preferential aggregation of the smaller particles in the propagation process leads to the change of the particles towards a uniform size and narrower particle size distribution.The coexistence and competition of homogeneous nucleation,coagulation,propagation and aggregation result in the increase of the polydispersity index(U=D43/D10) in the first stage,then its decrease in the later stage because of the competition of propagation and aggregation,and the gradual formation of the monodisperse particles.
2003, 21(1): 87-91
Abstract:
The blend film of silk fibroin (SF) and poly(ethylene glycol)400 (PEG400) with a blend ratio of 2/1 (wt/wt) wasprepared simply by dropping a little PEG400 into the SF solution and then casting the mixed aqueous solution at 50℃. Theresulting film exhibited much better mechanical properties in the dry and wet state than SF itself, owing to theconformational change of SF in the blends from the random coil to the β-sheet structure and intermolecular hydrogen bondformation between SF and PEG400.Thermogravimetric analysis showed that the initial thermal decomposition temoerature of the blend film was 170℃,which was 80℃ lower than that of SF(250℃) and 20℃ higher than that of PEG400(150℃),and indicated a strong interaction between two components of the blend.No crystalline peaks were observed in the X-ray diffraction curve of the blend film.Cell culture test showed that SF/PEG400 was a suitable substrate for the growth of human umbilical vein endothelial cells(HUVEC).
The blend film of silk fibroin (SF) and poly(ethylene glycol)400 (PEG400) with a blend ratio of 2/1 (wt/wt) wasprepared simply by dropping a little PEG400 into the SF solution and then casting the mixed aqueous solution at 50℃. Theresulting film exhibited much better mechanical properties in the dry and wet state than SF itself, owing to theconformational change of SF in the blends from the random coil to the β-sheet structure and intermolecular hydrogen bondformation between SF and PEG400.Thermogravimetric analysis showed that the initial thermal decomposition temoerature of the blend film was 170℃,which was 80℃ lower than that of SF(250℃) and 20℃ higher than that of PEG400(150℃),and indicated a strong interaction between two components of the blend.No crystalline peaks were observed in the X-ray diffraction curve of the blend film.Cell culture test showed that SF/PEG400 was a suitable substrate for the growth of human umbilical vein endothelial cells(HUVEC).
2003, 21(1): 93-98
Abstract:
An optically active polymer (PM1) containing azobenzene moieties with a chiral group (s-2-methyl-butyl) wassynthesized by homopolymerization of monomer, 4-[2-(methacryloyloxy)ethyloxy-4'-(s-2-methyl-1-butyl oxycarbonyl)azobenzene, using the free radical polymerization method. The polymer dissolved in tetrahydrofuran (THF) could be easilyprocessed into high optical quality films. The optical anisotropy of the polymer films was investigated by polarizing optical microscopy (POM).The experimental results showed that irradiation with a circularly polarized beam could align the orientation of the molecules in the polymer films.Moreover,the holographic phase gratings of photo-induced polymer films were detected by atomic force microscopy (AFM）and POM.In comparison with polymer containing no chiral group,it was found from the preliminary measurement of the photo-induced holographic phase gratings that PMI containing a chiral group could form holographic phase gratings buried in the films.
An optically active polymer (PM1) containing azobenzene moieties with a chiral group (s-2-methyl-butyl) wassynthesized by homopolymerization of monomer, 4-[2-(methacryloyloxy)ethyloxy-4'-(s-2-methyl-1-butyl oxycarbonyl)azobenzene, using the free radical polymerization method. The polymer dissolved in tetrahydrofuran (THF) could be easilyprocessed into high optical quality films. The optical anisotropy of the polymer films was investigated by polarizing optical microscopy (POM).The experimental results showed that irradiation with a circularly polarized beam could align the orientation of the molecules in the polymer films.Moreover,the holographic phase gratings of photo-induced polymer films were detected by atomic force microscopy (AFM）and POM.In comparison with polymer containing no chiral group,it was found from the preliminary measurement of the photo-induced holographic phase gratings that PMI containing a chiral group could form holographic phase gratings buried in the films.
2003, 21(1): 99-101
Abstract:
A new kind of organometallic precursor for Si/Zr/C/N-based ceramics was synthesized from the amine exchangereaction of hexamethylcyclotrisilazane (D3N) and tetrakis(diethylamino) zirconium (Zr[NEt2]4). Pyrolysis was performedunder nitrogen at 800℃ in a tube furnace equipped with a temperature program controller. The highest pyrolytic yield was67.5%.
A new kind of organometallic precursor for Si/Zr/C/N-based ceramics was synthesized from the amine exchangereaction of hexamethylcyclotrisilazane (D3N) and tetrakis(diethylamino) zirconium (Zr[NEt2]4). Pyrolysis was performedunder nitrogen at 800℃ in a tube furnace equipped with a temperature program controller. The highest pyrolytic yield was67.5%.
