Login In
1994 Volume 12 Issue 3
1994, 12(3): 193-200
Abstract:
A 13C-NMR method is presented for a quantitative determination of the respective monomercomposition and sequence distributions in ethylene-1-octene copolymers prepared with supportedtitanium/magnesium catalyst. On the basis of the sequence distributions, the ethylene-1-octenecopolymerization mechanism was studied. It was found that the observed sequence distributions inethylene-1-octene copolymers are satisfactorily predicted by the two-site model M/M,in whichthe copolymerization proceeds according to first-order Markovian statistics at the two different sites.
A 13C-NMR method is presented for a quantitative determination of the respective monomercomposition and sequence distributions in ethylene-1-octene copolymers prepared with supportedtitanium/magnesium catalyst. On the basis of the sequence distributions, the ethylene-1-octenecopolymerization mechanism was studied. It was found that the observed sequence distributions inethylene-1-octene copolymers are satisfactorily predicted by the two-site model M/M,in whichthe copolymerization proceeds according to first-order Markovian statistics at the two different sites.
1994, 12(3): 201-209
Abstract:
The thermal behavior, miscibility, crystallite conformation and thermal stability ofcrosslinked(CL-) PVA/PVP blends were studied by DSC and TG methods, respectively. DSCresults showed that in the blend, the crystallinity,Tm and Tc of PVA were obviously lower thanthose of pure PVA; the crystal growth changed from three dimensional to two dimensional andonly a single Tg was detected. These facts demonstrated that this crystalline and amorphousblend have good miscibility. TG curves showed that providing the quantity of K2S2O8 added is more than 3wt%,in the blends PVA will form a stable CL-network,whose thermal degradation temperature was near to that of PVP.But crosslinking reaction will not take place for PVP.The processes of thermal degradation of CL-blends are based on combining both the thermal degradation of PVP and that of PVA crosslinked with corresponding quantity of K2S2O8 CL-agent,respectively.The UV measurements showed that 75wt% of PVP may be remained in CL-blend hydrogels crosslinked by adding (3-5 wt%)K2S2O8.This is mainly due to the stable CL-network formed and the good compatibility and proper entanglement between the composites in the CL-blends.
The thermal behavior, miscibility, crystallite conformation and thermal stability ofcrosslinked(CL-) PVA/PVP blends were studied by DSC and TG methods, respectively. DSCresults showed that in the blend, the crystallinity,Tm and Tc of PVA were obviously lower thanthose of pure PVA; the crystal growth changed from three dimensional to two dimensional andonly a single Tg was detected. These facts demonstrated that this crystalline and amorphousblend have good miscibility. TG curves showed that providing the quantity of K2S2O8 added is more than 3wt%,in the blends PVA will form a stable CL-network,whose thermal degradation temperature was near to that of PVP.But crosslinking reaction will not take place for PVP.The processes of thermal degradation of CL-blends are based on combining both the thermal degradation of PVP and that of PVA crosslinked with corresponding quantity of K2S2O8 CL-agent,respectively.The UV measurements showed that 75wt% of PVP may be remained in CL-blend hydrogels crosslinked by adding (3-5 wt%)K2S2O8.This is mainly due to the stable CL-network formed and the good compatibility and proper entanglement between the composites in the CL-blends.
1994, 12(3): 210-220
Abstract:
A series of ethylene oxide-ethylene terephthalate segmented copolymers (EOET) weresynthesized and complexed with LiClO4 to form some new polymer electrolytes. The EOET-LiClO4 electrolytes exhibit not only high ionic conductivity, but also good mechanical strengthand toughness. The EOET 3400--25--LiClO4 complex possesses the highest conductivity (4. 65×10-5s·cm-1 at room temperature when the ratio [Li+]/[EO] equals 1/16. The structures of these electrolytes were examined with FTIR analysis, X-ray diffraction and DSC thermograms,and the results of high ionic conductivity of the segmented copolymers were discussed.
A series of ethylene oxide-ethylene terephthalate segmented copolymers (EOET) weresynthesized and complexed with LiClO4 to form some new polymer electrolytes. The EOET-LiClO4 electrolytes exhibit not only high ionic conductivity, but also good mechanical strengthand toughness. The EOET 3400--25--LiClO4 complex possesses the highest conductivity (4. 65×10-5s·cm-1 at room temperature when the ratio [Li+]/[EO] equals 1/16. The structures of these electrolytes were examined with FTIR analysis, X-ray diffraction and DSC thermograms,and the results of high ionic conductivity of the segmented copolymers were discussed.
1994, 12(3): 221-227
Abstract:
A new type of liquid crystalline polyesters with resorcin as one part of the mesogenic unitconnected together by polymethylene, or phenylene group, and lateral groups consisting of arigid azobenzene as another part of the mesogenic unit were synthesized by interfacialpolymerization of diacyl chlorides in 1, 2-dichloroethane and 2, 4-dihydroxy-4'-nitroazobenzen inaqueous alkaline solution. The polyester structures were confirmed by proton NMR and IRspectra. Their phase transition behavior and texture were studied by polarizing microscopy and DSC.
A new type of liquid crystalline polyesters with resorcin as one part of the mesogenic unitconnected together by polymethylene, or phenylene group, and lateral groups consisting of arigid azobenzene as another part of the mesogenic unit were synthesized by interfacialpolymerization of diacyl chlorides in 1, 2-dichloroethane and 2, 4-dihydroxy-4'-nitroazobenzen inaqueous alkaline solution. The polyester structures were confirmed by proton NMR and IRspectra. Their phase transition behavior and texture were studied by polarizing microscopy and DSC.
1994, 12(3): 228-236
Abstract:
Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials,the surface and tensile properties of these samples can be adjusted by various ratios of two soft segments.
Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials,the surface and tensile properties of these samples can be adjusted by various ratios of two soft segments.
1994, 12(3): 237-245
Abstract:
Fluorescence properties of 1-pheny1-3-(4'-nitrophenyl) pyrazoline (PNP) were studied inbulk polymerization process of methylmethacrylate (MMA). The fluorescence intensity of PNPwas enhanced and the emission maximum was blue shifted with the polymerization progress. Inthe period of auto-acceleration of the polymerization the enhancement of fluorescence intensityand blue shift of peak wavelength in spectra could be observed evidently. This means that thesolvatochromic properties of PNP are influenced not only by the solvent polarity but also by the viscosity of the medium (especially by the phase transition).In solid state PNP emits from the charge transfer excited state without solvent relaxation.The transient emission spectra and the results from Bakhshiev model of solvent relaxation coincide with that from the polymerization experiment.
Fluorescence properties of 1-pheny1-3-(4'-nitrophenyl) pyrazoline (PNP) were studied inbulk polymerization process of methylmethacrylate (MMA). The fluorescence intensity of PNPwas enhanced and the emission maximum was blue shifted with the polymerization progress. Inthe period of auto-acceleration of the polymerization the enhancement of fluorescence intensityand blue shift of peak wavelength in spectra could be observed evidently. This means that thesolvatochromic properties of PNP are influenced not only by the solvent polarity but also by the viscosity of the medium (especially by the phase transition).In solid state PNP emits from the charge transfer excited state without solvent relaxation.The transient emission spectra and the results from Bakhshiev model of solvent relaxation coincide with that from the polymerization experiment.
1994, 12(3): 246-255
Abstract:
The melting behavior of polypropylene (PP) and low ethylene content polypropylenecopolymer with and without nucleating agent samples crystallized under both isothermal and non-isothermal conditions were studied by Differential Scanning Calorimeter (DSC) and X-raydiffraction. Multiple melting behavior were observed depending on the existence of nucleatingagent and crystallization conditions. The observed phenomena have been discussed by the effect ofnucleating agent on perfection of crystal and the melting and recrystallization of imperfect crystal to a more perfect crystal during the heating process of samples.
The melting behavior of polypropylene (PP) and low ethylene content polypropylenecopolymer with and without nucleating agent samples crystallized under both isothermal and non-isothermal conditions were studied by Differential Scanning Calorimeter (DSC) and X-raydiffraction. Multiple melting behavior were observed depending on the existence of nucleatingagent and crystallization conditions. The observed phenomena have been discussed by the effect ofnucleating agent on perfection of crystal and the melting and recrystallization of imperfect crystal to a more perfect crystal during the heating process of samples.
1994, 12(3): 256-265
Abstract:
The classical crystallization theories proposed by Avrami, Evans, and Mandelkern wereextended to the nonisothermal situation. The expressions derived from the classical equations canbe expressed in either the differential form or the integral form. A method was provided so as toobtain the parameters characterizing the crystallization rate and mechanism from DSC curves withseveral constant heating or cooling rates. The rate constants of crystallization obtained from bothisothermal and nonisothermal curves of poly(ethylene terephethalate)were compared.
The classical crystallization theories proposed by Avrami, Evans, and Mandelkern wereextended to the nonisothermal situation. The expressions derived from the classical equations canbe expressed in either the differential form or the integral form. A method was provided so as toobtain the parameters characterizing the crystallization rate and mechanism from DSC curves withseveral constant heating or cooling rates. The rate constants of crystallization obtained from bothisothermal and nonisothermal curves of poly(ethylene terephethalate)were compared.
1994, 12(3): 266-277
Abstract:
Dynamic mechanical analysis was used to study the mechanical properties and microstructureof crazes in polystyrene produced in air or in methanol at different temperatures. A new loss peakwas found at about 82℃,which is assigned to glass transition peak of craze fibrils. The decreaseof glass transition temperature of polymer in craze fibrils is due to the high values of surface tovolume ratio. The glass transition temperature ratio of craze fibrils to bulk material (Tgl /Tg) hasbeen expressed as a function of the fibrils diameter(d).From Tg' of craze fibrils,the value of fibril diameter can be calculated.Annealing the crazed specimen at room temperature makes the fibrils plastically deform and cause the fibrils to thin slightly,whereas annealing the crazed specimen at the temperature near Tg of the craze fibrils makes the fibrils bundle together.
Dynamic mechanical analysis was used to study the mechanical properties and microstructureof crazes in polystyrene produced in air or in methanol at different temperatures. A new loss peakwas found at about 82℃,which is assigned to glass transition peak of craze fibrils. The decreaseof glass transition temperature of polymer in craze fibrils is due to the high values of surface tovolume ratio. The glass transition temperature ratio of craze fibrils to bulk material (Tgl /Tg) hasbeen expressed as a function of the fibrils diameter(d).From Tg' of craze fibrils,the value of fibril diameter can be calculated.Annealing the crazed specimen at room temperature makes the fibrils plastically deform and cause the fibrils to thin slightly,whereas annealing the crazed specimen at the temperature near Tg of the craze fibrils makes the fibrils bundle together.
1994, 12(3): 278-283
Abstract:
Based on the X-ray scattering intensity theory and using the atomic scattering factorapproximate expression,the correction factors for three main crystalline peaks and an amorphouspeak of Nylon-1010 were calculated and the formula of degree of crystallinity of Nylon-1010 wasderived by graphic multipeak resolution method. The results calculated are compatible with the density measurement and calorimetry.
Based on the X-ray scattering intensity theory and using the atomic scattering factorapproximate expression,the correction factors for three main crystalline peaks and an amorphouspeak of Nylon-1010 were calculated and the formula of degree of crystallinity of Nylon-1010 wasderived by graphic multipeak resolution method. The results calculated are compatible with the density measurement and calorimetry.
1994, 12(3): 284-288
Abstract:
A new cyclic monomer, 2-oxo-3-methylene-5, 6-diphenyl-1, 4-dioxan, was synthesized. Thestructure of the intermediates and the monomer were determined by IR,1H NMR,13C NMR andelemental analysis. This new monomer is different from other cyclic monomers in this series,it isa solid (mp 108--109℃)and not very reactive, but still can undergo free radical ring-openingpolymerization. The free radical polymerization was carried out at 130℃. The structure of theresulting polymer was discussed and charaterized by IR,1H NMR,13C NMR and elemental analysis.The molecular weight of the polymer was estimated by viscosity determination.3
A new cyclic monomer, 2-oxo-3-methylene-5, 6-diphenyl-1, 4-dioxan, was synthesized. Thestructure of the intermediates and the monomer were determined by IR,1H NMR,13C NMR andelemental analysis. This new monomer is different from other cyclic monomers in this series,it isa solid (mp 108--109℃)and not very reactive, but still can undergo free radical ring-openingpolymerization. The free radical polymerization was carried out at 130℃. The structure of theresulting polymer was discussed and charaterized by IR,1H NMR,13C NMR and elemental analysis.The molecular weight of the polymer was estimated by viscosity determination.3
