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2002 Volume 20 Issue 1
2002, 20(1): 1-7
Abstract:
Multilayer thin films of alternately adsorbed layers of polyelectrolytes PDDA and PS-119 were formed on bothplanar silica substrates and optical fibers through the ionic self-assembly technique. Intrinsic Fabry-Perot cavities werefabricated by stepwise assembling the polyelectrolytes onto the ends of optical fibers for the purposes of fiber optical deviceand sensor development. Ionically assembled polyelectrolyte multilayer thin films, in which there are hydrophilic side groups with strong affinity towards water molecules,are a category of humidity-sensitive functional materials.The polyelectrolyte multilayer thin film Fabry-Perot cavity-type fiber optical humidity sensor can work over a wide range from about 0% RH to about 100% RH with a response time less than 1 s.
Multilayer thin films of alternately adsorbed layers of polyelectrolytes PDDA and PS-119 were formed on bothplanar silica substrates and optical fibers through the ionic self-assembly technique. Intrinsic Fabry-Perot cavities werefabricated by stepwise assembling the polyelectrolytes onto the ends of optical fibers for the purposes of fiber optical deviceand sensor development. Ionically assembled polyelectrolyte multilayer thin films, in which there are hydrophilic side groups with strong affinity towards water molecules,are a category of humidity-sensitive functional materials.The polyelectrolyte multilayer thin film Fabry-Perot cavity-type fiber optical humidity sensor can work over a wide range from about 0% RH to about 100% RH with a response time less than 1 s.
2002, 20(1): 9-14
Abstract:
Polymerization of three cyclic ketene acetals: i.e., 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-4-phenyl-1,3-dioxolane (MPDO) and 4, 7-dimethyl-2-methylene-1, 3-dioxepane(DMMDO) were carried out in the presence ofethyl α-bromobutyrate/CuBr/2, 2'-bipyridine respectively. The structures of poly(BMDO), poly(MPDO) and poly(DMMDO)were characterized by 1H and 13C-NMR spectra. The effects of monomer structure on the behavior of atom transfer freeradical ring-opening polymerization were investigated and the mechanism of controlled free radical ring-opening polymerization was discussed.
Polymerization of three cyclic ketene acetals: i.e., 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-4-phenyl-1,3-dioxolane (MPDO) and 4, 7-dimethyl-2-methylene-1, 3-dioxepane(DMMDO) were carried out in the presence ofethyl α-bromobutyrate/CuBr/2, 2'-bipyridine respectively. The structures of poly(BMDO), poly(MPDO) and poly(DMMDO)were characterized by 1H and 13C-NMR spectra. The effects of monomer structure on the behavior of atom transfer freeradical ring-opening polymerization were investigated and the mechanism of controlled free radical ring-opening polymerization was discussed.
2002, 20(1): 15-23
Abstract:
Fluorescence spectra of ladderlike polyphenylsilsesquioxane (LPPS) and ladderlike 1,4-phenylene-bridgedpolyvinylsiloxane (LPPVS) have been measured as a function of temperature (4-55℃), in dilute tetrahydrofuran solution.The excimer (IE) to monomer (IM) intensity ratio (IE/IM) of LPPS dilute solution shows a double linear Arrhenius plot with abreak point ascribable to a transition temperature Tt This behavior has not been found for single chain polyorganosiloxanes.When lnIE of LPPS was plotted against 1/T,it also gave a double linear plot with one break point,which was found in single chain polyorganosiloxanes.The different behaviors between LPPS and single chain polyorganosiloxanes may be mainly attributed to the relatively rigid double-chain macromolecular backbone of LPPS.However,the ln(IE/IM) of dilute LPPVS solution versus 1/T shows a simple linear variation with a positive slope which confirms our proposition.The difference between the fluorescence results of LPPS and those of LPPVS may possibly derive from their structure difference and cooperative motion in backbone chain bonds.
Fluorescence spectra of ladderlike polyphenylsilsesquioxane (LPPS) and ladderlike 1,4-phenylene-bridgedpolyvinylsiloxane (LPPVS) have been measured as a function of temperature (4-55℃), in dilute tetrahydrofuran solution.The excimer (IE) to monomer (IM) intensity ratio (IE/IM) of LPPS dilute solution shows a double linear Arrhenius plot with abreak point ascribable to a transition temperature Tt This behavior has not been found for single chain polyorganosiloxanes.When lnIE of LPPS was plotted against 1/T,it also gave a double linear plot with one break point,which was found in single chain polyorganosiloxanes.The different behaviors between LPPS and single chain polyorganosiloxanes may be mainly attributed to the relatively rigid double-chain macromolecular backbone of LPPS.However,the ln(IE/IM) of dilute LPPVS solution versus 1/T shows a simple linear variation with a positive slope which confirms our proposition.The difference between the fluorescence results of LPPS and those of LPPVS may possibly derive from their structure difference and cooperative motion in backbone chain bonds.
2002, 20(1): 25-30
Abstract:
In this paper, an atificial neural network model is adopted to study the glass transition temperature of polymers. Inour artificial neural networks, the input nodes are the characteristic ratio C∞, the average molecular weigh Me betweenentanglement points and the molecular weigh Mmon of repeating unit. The output node is the glass transition temperature Tg,and the number of the hidden layer is 6. We found that the artificial neural network simulations are accurate in predicting the outcome for polymers for which it is not trained.The maximum relative error for predicting of the glass transition temperature is 3.47%,and the overall average error is only 2.27%.Artificial neural networks may provide some new ideas to investigate other properties of the polymers.
In this paper, an atificial neural network model is adopted to study the glass transition temperature of polymers. Inour artificial neural networks, the input nodes are the characteristic ratio C∞, the average molecular weigh Me betweenentanglement points and the molecular weigh Mmon of repeating unit. The output node is the glass transition temperature Tg,and the number of the hidden layer is 6. We found that the artificial neural network simulations are accurate in predicting the outcome for polymers for which it is not trained.The maximum relative error for predicting of the glass transition temperature is 3.47%,and the overall average error is only 2.27%.Artificial neural networks may provide some new ideas to investigate other properties of the polymers.
2002, 20(1): 31-38
Abstract:
The one plus one (1 + 1) mode of hydrosilation reaction of ladderlike cis-isotatic polyallylsilsesquioxane (Allyl-T)and polyhydrosilsesquioxane (H-T) using dicyclopentadienylplatinumdichloride (Cp2PtCl2) as the catalyst leads to theformation of a new polyorganosiloxane (POS). The presence of nanoscale tubular structure in the product POS waspreliminarily proved by IR, 1H-NMR, differential scanning calorimetry (DSC), X-ray diffraction (XRD), gel permeation chromatography (GPC), atomic force microscopy(AFM)and molecular simulation.
The one plus one (1 + 1) mode of hydrosilation reaction of ladderlike cis-isotatic polyallylsilsesquioxane (Allyl-T)and polyhydrosilsesquioxane (H-T) using dicyclopentadienylplatinumdichloride (Cp2PtCl2) as the catalyst leads to theformation of a new polyorganosiloxane (POS). The presence of nanoscale tubular structure in the product POS waspreliminarily proved by IR, 1H-NMR, differential scanning calorimetry (DSC), X-ray diffraction (XRD), gel permeation chromatography (GPC), atomic force microscopy(AFM)and molecular simulation.
2002, 20(1): 39-44
Abstract:
New IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule,kappa-carrageenan (KC) were prepared by gamma irradiation and their properties were studied. The results show that boththe gel strength and the swelling capacity of the IPN hydrogels were enhanced significantly as compared with those of thepure hydrogels of PDADMAC.
New IPN hydrogels composed of diallyldimethylammonium chloride (DADMAC) and natural macromolecule,kappa-carrageenan (KC) were prepared by gamma irradiation and their properties were studied. The results show that boththe gel strength and the swelling capacity of the IPN hydrogels were enhanced significantly as compared with those of thepure hydrogels of PDADMAC.
2002, 20(1): 45-51
Abstract:
Poly(ε-caprolactone) (PCL) with different molecular weights was synthesized and characterized by a gelpermeation chromatograph equipped with multiple detector. The melting behavior of PCL was also studied. It was found thatthe equilibrium melting points (Tm0) of PCL samples depend on their molecular weights. Wide angle X-ray diffractionmeasurements (WAXD) and DSC measurements showed that the crystals of the high molecular weight PCLs were more perfect than those of the low molecular weight ones.These results demonstrate that the concentration of the end groups of PCL chains is the main factor that influences the melting behavior.The fusion enthalpy per repeating unit (△Hu) was determined to be 11.3 kJmol for PCL.
Poly(ε-caprolactone) (PCL) with different molecular weights was synthesized and characterized by a gelpermeation chromatograph equipped with multiple detector. The melting behavior of PCL was also studied. It was found thatthe equilibrium melting points (Tm0) of PCL samples depend on their molecular weights. Wide angle X-ray diffractionmeasurements (WAXD) and DSC measurements showed that the crystals of the high molecular weight PCLs were more perfect than those of the low molecular weight ones.These results demonstrate that the concentration of the end groups of PCL chains is the main factor that influences the melting behavior.The fusion enthalpy per repeating unit (△Hu) was determined to be 11.3 kJmol for PCL.
2002, 20(1): 53-57
Abstract:
This paper investigates the possibility of attaining sulphonated poly(phenylene oxide) (SPPO) with a relativelyhigher sulfonation degree. To achieve this aim, the approach we adopt is to improve the solubility of the final product in themixed solvent so that the sulfonation may take place between the bulk solutions and PPO powders even at higher sulfonationdegree. It is shown that the addition of a proper amount of dimethyl formide (DMF) to the conventional PPO-chloroform system can actually enhance the sulfonation effect.The solvent composition is then correlated with the sulfonation degree based on the solubility parameters.It is interesting to find that solubility parameters between the mixed solvent and the precipitated products keep an approximately nuchanged value at about 4.9,which is just equal to that when pure chloroform is used,though the solubility parameters of both solvents increase with the content of DMF in solution.This may be the main reason why the addition of DMF can reduce the precipitation and improve the ion exchange capacity (IEC) of SPPO polymer.
This paper investigates the possibility of attaining sulphonated poly(phenylene oxide) (SPPO) with a relativelyhigher sulfonation degree. To achieve this aim, the approach we adopt is to improve the solubility of the final product in themixed solvent so that the sulfonation may take place between the bulk solutions and PPO powders even at higher sulfonationdegree. It is shown that the addition of a proper amount of dimethyl formide (DMF) to the conventional PPO-chloroform system can actually enhance the sulfonation effect.The solvent composition is then correlated with the sulfonation degree based on the solubility parameters.It is interesting to find that solubility parameters between the mixed solvent and the precipitated products keep an approximately nuchanged value at about 4.9,which is just equal to that when pure chloroform is used,though the solubility parameters of both solvents increase with the content of DMF in solution.This may be the main reason why the addition of DMF can reduce the precipitation and improve the ion exchange capacity (IEC) of SPPO polymer.
2002, 20(1): 59-64
Abstract:
In the present paper, the behavior of a single polymer chain under various solvent conditions was modeled by self-avoiding walks (SAW) with nearest neighbors attraction Δε on a simple cubic lattice. Determination of the θ-condition wasbased on the numerical results of the mean square radius of gyration and end-to-end distance. It was found that at the θtemperatue Δε/kT equals -0.27. The exponents a in the Mark-Houwink equation with different interaction parameters are consistent with the results of experiments:under θ-condition,α=0.74-0.84,respectively.
In the present paper, the behavior of a single polymer chain under various solvent conditions was modeled by self-avoiding walks (SAW) with nearest neighbors attraction Δε on a simple cubic lattice. Determination of the θ-condition wasbased on the numerical results of the mean square radius of gyration and end-to-end distance. It was found that at the θtemperatue Δε/kT equals -0.27. The exponents a in the Mark-Houwink equation with different interaction parameters are consistent with the results of experiments:under θ-condition,α=0.74-0.84,respectively.
2002, 20(1): 65-70
Abstract:
A kind of aziridine crosslinkers was synthesized and used to crosslink acrylate copolymers. The crosslinkingproperties and curing kinetics of the resin were studied. It was found that with the increase of the content of crosslinker in theemulsion, the mechanical properties and solvent resistance of the resin will be apparently improved, but its glass transitiontemperature (Tg) is very low. The lowest amount of crosslinker used in the acrylic resin emulsion is 0.25%. Curing kinetics studied by DSC show that this curing reaction occurs readily because the apparent activation energy of the reaction is low (65.1kJ/mol).These results demonstrate that the aziridine crosslinker is indeed a low temperature crosslinking agent and can be used at room temperature.
A kind of aziridine crosslinkers was synthesized and used to crosslink acrylate copolymers. The crosslinkingproperties and curing kinetics of the resin were studied. It was found that with the increase of the content of crosslinker in theemulsion, the mechanical properties and solvent resistance of the resin will be apparently improved, but its glass transitiontemperature (Tg) is very low. The lowest amount of crosslinker used in the acrylic resin emulsion is 0.25%. Curing kinetics studied by DSC show that this curing reaction occurs readily because the apparent activation energy of the reaction is low (65.1kJ/mol).These results demonstrate that the aziridine crosslinker is indeed a low temperature crosslinking agent and can be used at room temperature.
2002, 20(1): 71-76
Abstract:
The grafting of polystyrene onto a nanometer silica surface by microemulsion polymerization is described. Silicawas functionalized with 3-methacryloxypropyltrimethoxysilane coupling agent before polymerization. A mixture of ionic andnon-ionic surfactants as well as water-soluble and oil-soluble initiators were used. The effect of the amount of silica and ionicsurfactant on the graft polymerization was studied. The graft polymerization procedure for styrene was also applied to methyl methacrylate.Composite particles with a core-shell structure were obtained and the yield and grafting efficiency of monomer were high.
The grafting of polystyrene onto a nanometer silica surface by microemulsion polymerization is described. Silicawas functionalized with 3-methacryloxypropyltrimethoxysilane coupling agent before polymerization. A mixture of ionic andnon-ionic surfactants as well as water-soluble and oil-soluble initiators were used. The effect of the amount of silica and ionicsurfactant on the graft polymerization was studied. The graft polymerization procedure for styrene was also applied to methyl methacrylate.Composite particles with a core-shell structure were obtained and the yield and grafting efficiency of monomer were high.
STUDY ON THE OXIDIZED GRAPHITE MATERIAL COATED WITH N-DOPED PHENOLIC RESIN FOR LITHIUM ION BATTERIES
2002, 20(1): 77-80
Abstract:
Carbon-coated oxidized graphite has been prepared by a liquid-state deposition method. Oxidized graphite wasprepared by wet chemical oxidation. Oxidation increases the reversible capacity of graphite, but its initial charge anddischarge efficiency was reduced. Phenolic resin was applied to form the disordered carbon layer on the oxidized graphite.The efficiency and reversible charge capacity were obviously increased. The morphology of carbon materials wasinvestigated by SEM.
Carbon-coated oxidized graphite has been prepared by a liquid-state deposition method. Oxidized graphite wasprepared by wet chemical oxidation. Oxidation increases the reversible capacity of graphite, but its initial charge anddischarge efficiency was reduced. Phenolic resin was applied to form the disordered carbon layer on the oxidized graphite.The efficiency and reversible charge capacity were obviously increased. The morphology of carbon materials wasinvestigated by SEM.
