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2000 Volume 18 Issue 4
2000, 18(4): 287-300
Abstract:
Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (DCF) diblock copolymer,the competition between crystallization of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-ray scattering (SAXS) and wide angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques.In the case of TcTgPS-rich,the crystallization of the PEO blocks is observed to be confined within the bicontinuous DCF phase due to the rapid vitrification of the PS-rich phase.Overall crystallization rate,crystal melting behavior,and crystallinity results further confirm the competition between crystallization and vitrification at different temperatures.In an ordered lamellar PEO-bPS diblock copolymer,the crystallization of the PEO blocks is completely confined within the ordered lamellae due to rapid vitrification of the PS layers as observed by time-resolved SAXS and WAXD experiments.From the combined two-dimensional SAXS and WAXD measurements,the crystal orientation within the confined lamellar geometry is found parallel to the lamellar surface normal when it is isothermally crystallized at 35℃.In an ordered cylindrical PEO-b-PS sample,the crystallization of the PEO blocks is also observed to be confined within the ordered cylinders because of rapid vitrification of the PS matrix.The crystal orientation within the confined cylinders is found perpendicular to the cylinder axis as it is crystallized at 35℃.
Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (DCF) diblock copolymer,the competition between crystallization of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-ray scattering (SAXS) and wide angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques.In the case of TcTgPS-rich,the crystallization of the PEO blocks is observed to be confined within the bicontinuous DCF phase due to the rapid vitrification of the PS-rich phase.Overall crystallization rate,crystal melting behavior,and crystallinity results further confirm the competition between crystallization and vitrification at different temperatures.In an ordered lamellar PEO-bPS diblock copolymer,the crystallization of the PEO blocks is completely confined within the ordered lamellae due to rapid vitrification of the PS layers as observed by time-resolved SAXS and WAXD experiments.From the combined two-dimensional SAXS and WAXD measurements,the crystal orientation within the confined lamellar geometry is found parallel to the lamellar surface normal when it is isothermally crystallized at 35℃.In an ordered cylindrical PEO-b-PS sample,the crystallization of the PEO blocks is also observed to be confined within the ordered cylinders because of rapid vitrification of the PS matrix.The crystal orientation within the confined cylinders is found perpendicular to the cylinder axis as it is crystallized at 35℃.
2000, 18(4): 301-307
Abstract:
He, CO2, O2, N2, CH4, C3H8, and t-C4H_10 gas permeability coefficients and diffusion coefficients of poly(4-methylpentene-1) (PMP) with various degrees of crystallization were plotted against the degree of crystallization. The plotdemonstrated a linear relationship. The gas permeability coefficient and diffusion coefficient of pure amorphous and purecrystalline PMPs were evaluated by a linear extrapolation to zero and 100% crystallinity, respectively. The relationship between the diffusion coefficient of crystalline parts of PMP and the kinetic diameter of penetrant gases was discussed.Syndiotactic polystyrene (SPS) could exist as δ form crystals complexed with organic solvents such as benzene,toluene,xylene,and ethylbenzene.The mesophase of SPS is prepared by annealing the δform of crystalline complexes at a certain temperature for 1 h.The desorption of solvent during annealing almost does not result in changes of both the comformation of backbone chains and the crystal lattice.We could prepare the mesophase containing molecular cavities with the size and shape of the organic solvent molecules.The mesophase could sorb the same solvent after the manner of Langmuir sorption at low vapor pressure range while this would not be the case for solvents of different size and shape.This suggests a molecular recognition of organic solvent,and mesophase SPS might be useful for reparation membrane and adsorptive material.
He, CO2, O2, N2, CH4, C3H8, and t-C4H_10 gas permeability coefficients and diffusion coefficients of poly(4-methylpentene-1) (PMP) with various degrees of crystallization were plotted against the degree of crystallization. The plotdemonstrated a linear relationship. The gas permeability coefficient and diffusion coefficient of pure amorphous and purecrystalline PMPs were evaluated by a linear extrapolation to zero and 100% crystallinity, respectively. The relationship between the diffusion coefficient of crystalline parts of PMP and the kinetic diameter of penetrant gases was discussed.Syndiotactic polystyrene (SPS) could exist as δ form crystals complexed with organic solvents such as benzene,toluene,xylene,and ethylbenzene.The mesophase of SPS is prepared by annealing the δform of crystalline complexes at a certain temperature for 1 h.The desorption of solvent during annealing almost does not result in changes of both the comformation of backbone chains and the crystal lattice.We could prepare the mesophase containing molecular cavities with the size and shape of the organic solvent molecules.The mesophase could sorb the same solvent after the manner of Langmuir sorption at low vapor pressure range while this would not be the case for solvents of different size and shape.This suggests a molecular recognition of organic solvent,and mesophase SPS might be useful for reparation membrane and adsorptive material.
2000, 18(4): 309-322
Abstract:
This research studied the initiator efficiency for producing polymeric particles of poly(styrene-co-methylmethacrylate) copolymers by a Shirasu porous glass membrane (SPG) emulsification technique followed by suspensioncopolymerization. BPO, ADVN, and AIBN were used as initiators and we found that BPO is the most suitable initiator.Copolymers for various feed ratios of styrene/methyl methacrylate were thus synthesized by benzoyl peroxide, and theircopolymer particle size, molecular weight distribution and particle size distribution were characterized.Then n-BMA or 2-EHMA was added as the third monomer to decrease the terpolymer glass transition temperature.This article describes the preparation technique,recipes and polymerization conditions for producing both copolymer and terpolymer particles,particle size changes,the corresponding particle morphologies and glass transition temperatures.
This research studied the initiator efficiency for producing polymeric particles of poly(styrene-co-methylmethacrylate) copolymers by a Shirasu porous glass membrane (SPG) emulsification technique followed by suspensioncopolymerization. BPO, ADVN, and AIBN were used as initiators and we found that BPO is the most suitable initiator.Copolymers for various feed ratios of styrene/methyl methacrylate were thus synthesized by benzoyl peroxide, and theircopolymer particle size, molecular weight distribution and particle size distribution were characterized.Then n-BMA or 2-EHMA was added as the third monomer to decrease the terpolymer glass transition temperature.This article describes the preparation technique,recipes and polymerization conditions for producing both copolymer and terpolymer particles,particle size changes,the corresponding particle morphologies and glass transition temperatures.
2000, 18(4): 323-336
Abstract:
The self-assembling behavior of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS)and hydrophobic comonomers possessing dodecyl groups linked by various spacer bonds was discussed with a focus on theeffect of the spacer. The characterization of association behavior of such polymers in water using quasielastic light scattering,capillary electrophoresis, NMR relaxation, various fluorescence, and viscoelastic methods was described. These copolymers form a cariety of self-assembled nanostructures depending on the type of the spacer.Random copolymers of AMPS and N-dodecylmethacrylamide show a strong preference for intrapolymer self-association even in concentrated aqueous solutions forming single-macromolecular self-assemblies (unimolecular micelles).In contrast,random copolymers of AMPS and dodecyl methacrylate are prone to undergo interpolymer associations yielding multipolymer mucelles.In random copolymers of AMPS and a methacrylate substituted a nonionic surfactant (HO(CH2CH2O)25C12H25)(C12E25),dodecyl groups are much less restricted by the polymer backbone because they are linked via a long,flexible hydrophilic spacer.Thus,the polymer-bound C12E25 surfactant moieties form micelles similar to those formed by discrete surfactants,but they are bridged by polymer chains forming a network structure.
The self-assembling behavior of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS)and hydrophobic comonomers possessing dodecyl groups linked by various spacer bonds was discussed with a focus on theeffect of the spacer. The characterization of association behavior of such polymers in water using quasielastic light scattering,capillary electrophoresis, NMR relaxation, various fluorescence, and viscoelastic methods was described. These copolymers form a cariety of self-assembled nanostructures depending on the type of the spacer.Random copolymers of AMPS and N-dodecylmethacrylamide show a strong preference for intrapolymer self-association even in concentrated aqueous solutions forming single-macromolecular self-assemblies (unimolecular micelles).In contrast,random copolymers of AMPS and dodecyl methacrylate are prone to undergo interpolymer associations yielding multipolymer mucelles.In random copolymers of AMPS and a methacrylate substituted a nonionic surfactant (HO(CH2CH2O)25C12H25)(C12E25),dodecyl groups are much less restricted by the polymer backbone because they are linked via a long,flexible hydrophilic spacer.Thus,the polymer-bound C12E25 surfactant moieties form micelles similar to those formed by discrete surfactants,but they are bridged by polymer chains forming a network structure.
2000, 18(4): 337-342
Abstract:
Several kinds of novel azobenzene-containing polyelectrolytes with special molecular design have been developedfrom acryloyl chloride or epoxy based precursor polymers. The acryloyl chloride based precursor polymer, poly(acryloylchloride), was prepared by free radical polymerization of acryloyl chloride. The azo polyelectrolytes were prepared by anesterification reaction between the precursor polymer and corresponding azo chromophores containing a reactive hydroxyl group,followed by hydrolysis of the unreacted acyl chloride groups.The epoxy based precursor polymer was prepared by the reaction between 1,4-cyclohexanedimethanol diglycidyl ether and aniline,and postfunctionallized by azo coupling reaction to form azo polymers containing chromophores with ionizable groups.The polyelectrolytes were characterized by elemental analysis,1H-NMR,IR and UV-Vis spectroscopy.The photodynamic and photoresponsive properties,as well as self-assembly of these azo polyelectrolytes are reported in this paper[1].
Several kinds of novel azobenzene-containing polyelectrolytes with special molecular design have been developedfrom acryloyl chloride or epoxy based precursor polymers. The acryloyl chloride based precursor polymer, poly(acryloylchloride), was prepared by free radical polymerization of acryloyl chloride. The azo polyelectrolytes were prepared by anesterification reaction between the precursor polymer and corresponding azo chromophores containing a reactive hydroxyl group,followed by hydrolysis of the unreacted acyl chloride groups.The epoxy based precursor polymer was prepared by the reaction between 1,4-cyclohexanedimethanol diglycidyl ether and aniline,and postfunctionallized by azo coupling reaction to form azo polymers containing chromophores with ionizable groups.The polyelectrolytes were characterized by elemental analysis,1H-NMR,IR and UV-Vis spectroscopy.The photodynamic and photoresponsive properties,as well as self-assembly of these azo polyelectrolytes are reported in this paper[1].
2000, 18(4): 343-349
Abstract:
Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH=6.0～7.0, vinylene carbonate(VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reverse-phase suspensionpolymerization and hydrophilic copolymeric supports were prepared. The properties of the supports were determined usingtrypsin and results show that the amount of enzymes coupled to the supports and the specific activity of immobilized trypsinare related to the content of VCA structure units,reaction time and concentration of enzyme solution,etc.
Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH=6.0～7.0, vinylene carbonate(VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reverse-phase suspensionpolymerization and hydrophilic copolymeric supports were prepared. The properties of the supports were determined usingtrypsin and results show that the amount of enzymes coupled to the supports and the specific activity of immobilized trypsinare related to the content of VCA structure units,reaction time and concentration of enzyme solution,etc.
2000, 18(4): 351-356
Abstract:
The photopolymerization of two kinds of prepolyesters containing conjugated diacetylene (PDA-6 and PDA-12)was investigated using DSC. By measuring the endothermic enthalpy of the prepolymers after different UV-irradiation times,the polymerizations were found to follow the first-order rate law which agreed with the results of other investigators using adifferent method. The endothermic enthalpy measurements of PDA-6 and PDA-12 before UV-irradiation precluded the possibility that the decrease of endothermic enthalpy was caused by thermal polymerization.
The photopolymerization of two kinds of prepolyesters containing conjugated diacetylene (PDA-6 and PDA-12)was investigated using DSC. By measuring the endothermic enthalpy of the prepolymers after different UV-irradiation times,the polymerizations were found to follow the first-order rate law which agreed with the results of other investigators using adifferent method. The endothermic enthalpy measurements of PDA-6 and PDA-12 before UV-irradiation precluded the possibility that the decrease of endothermic enthalpy was caused by thermal polymerization.
2000, 18(4): 357-361
Abstract:
The thermally stimulated shape memory behavior of ethylene oxide-butylene terephthalate (EOBT) segmentedcopolymers with different soft segment molecular weight and hard segment content was investigated. The deformationrecovery ratio Rf of the EOBT samples increases with the soft segment molecular weight and the hard segment weightcontent, while the average overall deformation recovery speed Vr increases with the hard segment content. The temperatureof maximum deformation recovery speed (TM) is determined by the melting temperature of the soft segment crystals and the stability of the crystallized hard segment domains.
The thermally stimulated shape memory behavior of ethylene oxide-butylene terephthalate (EOBT) segmentedcopolymers with different soft segment molecular weight and hard segment content was investigated. The deformationrecovery ratio Rf of the EOBT samples increases with the soft segment molecular weight and the hard segment weightcontent, while the average overall deformation recovery speed Vr increases with the hard segment content. The temperatureof maximum deformation recovery speed (TM) is determined by the melting temperature of the soft segment crystals and the stability of the crystallized hard segment domains.
2000, 18(4): 363-367
Abstract:
A detailed study was performed on the crystal structures of pan-milled high-density polyethylene (HDPE) usingdifferential scanning calorimetry (DSC) and X-ray diffraction. The crystallinity of HDPE first decreased slightly, followed bya gradual increase with increasing milling times. Monoclinic crystals appeared after 4 cycles of milling. With increasingtimes of milling, the proportion of monoclinic crystals increased significantly while the proportion of orthorhombic crystallites kept almost constant during milling.
A detailed study was performed on the crystal structures of pan-milled high-density polyethylene (HDPE) usingdifferential scanning calorimetry (DSC) and X-ray diffraction. The crystallinity of HDPE first decreased slightly, followed bya gradual increase with increasing milling times. Monoclinic crystals appeared after 4 cycles of milling. With increasingtimes of milling, the proportion of monoclinic crystals increased significantly while the proportion of orthorhombic crystallites kept almost constant during milling.
2000, 18(4): 369-372
Abstract:
A rare earth coordination system was first investigated as a new type of catalyst for the ring-openingpolymerization of α-amino acid N-carboxyanhydrides (NCAs). The results for the polymerization of γ-stearyl-α,L-glutamate(SLG) NCA using neodymium acetylacetonate (Nd(acac)3)- or neodymium tris(2-ethylhexylphosphonate) (Nd(P204)3)-triethylaluminum-water as catalysts were compared with those using conventional catalysts. It was found that the helicalpoly(γ-stearyl-L-glutamate) with high molecular weight as well as narrow molecular weight distribution can be obtained in the presence of Nd(acac)3/ALEt3-1/2H2O.The polymer obtained was characterized by IR and NMR spectroscopy.
A rare earth coordination system was first investigated as a new type of catalyst for the ring-openingpolymerization of α-amino acid N-carboxyanhydrides (NCAs). The results for the polymerization of γ-stearyl-α,L-glutamate(SLG) NCA using neodymium acetylacetonate (Nd(acac)3)- or neodymium tris(2-ethylhexylphosphonate) (Nd(P204)3)-triethylaluminum-water as catalysts were compared with those using conventional catalysts. It was found that the helicalpoly(γ-stearyl-L-glutamate) with high molecular weight as well as narrow molecular weight distribution can be obtained in the presence of Nd(acac)3/ALEt3-1/2H2O.The polymer obtained was characterized by IR and NMR spectroscopy.
2000, 18(4): 373-377
Abstract:
In situ interferometry was used to investigate the gelation process of polyacrylic acid (PAA) gels. The basicprinciple of the in situ interferometry technique is illustrated. It can give sufficient information for non-destructive andsuccessful investigation of the whole gelation process. The effect of initiator concentration on the gelation process wasstudied. The polymerization rate of AA increases with increasing initiator concentration. The error arising from the thermal effect in the gelation process can be neglected.
In situ interferometry was used to investigate the gelation process of polyacrylic acid (PAA) gels. The basicprinciple of the in situ interferometry technique is illustrated. It can give sufficient information for non-destructive andsuccessful investigation of the whole gelation process. The effect of initiator concentration on the gelation process wasstudied. The polymerization rate of AA increases with increasing initiator concentration. The error arising from the thermal effect in the gelation process can be neglected.
