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1997 Volume 15 Issue 3
1997, 15(3): 193-198
Abstract:
Light transmission spectra of THF solutions of poly (C60-co-methyl methacrylate)s andpoly (C60-co-styrene)s continuously red-shift with increasing concentration. Formation offullerene nanoclusters may be responsible for the unusual spectral shift with concentration.It has long been scientists' dream to "tune" material's properties by simple means, and theC60-containing polymers represent such a group of novel materials whose optical propertiesare predictably and reversibly tunable by a simple change in concentration.
Light transmission spectra of THF solutions of poly (C60-co-methyl methacrylate)s andpoly (C60-co-styrene)s continuously red-shift with increasing concentration. Formation offullerene nanoclusters may be responsible for the unusual spectral shift with concentration.It has long been scientists' dream to "tune" material's properties by simple means, and theC60-containing polymers represent such a group of novel materials whose optical propertiesare predictably and reversibly tunable by a simple change in concentration.
1997, 15(3): 199-204
Abstract:
The isotropy or anisotropy in some physical properties of the ammorphous poly(ethyleneterephthalate) films uniaxially drawn at temperatures above its Tg and then quenched toroom temperature have been studied. Experimental results here presented show that thisamorphous state of high global chain orientation but nearly random segmental orientation,the GOLR state, is nearly isotropic in refractive indices and Young's modulus for smalldeformation, while it is very probably anisotropic in thermal conduction and microwave dielectric properties.
The isotropy or anisotropy in some physical properties of the ammorphous poly(ethyleneterephthalate) films uniaxially drawn at temperatures above its Tg and then quenched toroom temperature have been studied. Experimental results here presented show that thisamorphous state of high global chain orientation but nearly random segmental orientation,the GOLR state, is nearly isotropic in refractive indices and Young's modulus for smalldeformation, while it is very probably anisotropic in thermal conduction and microwave dielectric properties.
1997, 15(3): 205-216
Abstract:
In situ compatibilization of low density polyehylene (LDPE) (30%) and nylon-6(70%)blends through one-step reactive extrusion using t-BuOOH as an initiator and low molec-ular weight interfacial agents as compatibilizers was studied. The compatibilizer containeda long chain bydrocarbon, double bond and two polar functional groups which was capableof reacting with both LDPE and nylon-6 in the presence of initiator to form a copolymerat the interface of the two polymer phases. The extruded blends exhibited significant enhancement in their compatibility based on morphological,thermal analysis and mechanical studies.The effect of the hydrocarbon chain length and structure of the functional group of the compatibilizer was also examined.It was found that blends prepared by using the compatibilizer containing longer hydrocarbon chain and amide group had better mechanical properties.
In situ compatibilization of low density polyehylene (LDPE) (30%) and nylon-6(70%)blends through one-step reactive extrusion using t-BuOOH as an initiator and low molec-ular weight interfacial agents as compatibilizers was studied. The compatibilizer containeda long chain bydrocarbon, double bond and two polar functional groups which was capableof reacting with both LDPE and nylon-6 in the presence of initiator to form a copolymerat the interface of the two polymer phases. The extruded blends exhibited significant enhancement in their compatibility based on morphological,thermal analysis and mechanical studies.The effect of the hydrocarbon chain length and structure of the functional group of the compatibilizer was also examined.It was found that blends prepared by using the compatibilizer containing longer hydrocarbon chain and amide group had better mechanical properties.
1997, 15(3): 217-225
Abstract:
The composition distribution (CD) and microisotacticity distribution (ID) of propene/1-hexene copolymer synthesized by MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) weredetermined by fractionating the copolymers according to crystallinity and characterizingthe fractions by 13CNMR. The effects of two alkoxysilane donors, triethoxyphenylsilane(PTES) and dimethoxydi-tert-butylsilane (TBMS), on CD and ID of the copolymrs werecompared. Three main parts in the CD diagram of each copolymer were distinguished,which were correlated to active center distribution (ACD) based on three groups of different active centers.By studying the changes in 1-hexene content,microisotacticity and reactivity ratio product of three typical fractions,the effects of external donor on ACD were better elucidated.It was found that TBMS shows much stronger effects on ACD than PTES.In the former system,most fractions were produced on active centers with relatively lower r1 r2,higher reactivity to 1-hexene,and higher stereospecificity as compared to the system without external donor.It is concluded that the observed very extensive changes in ACD are mainly resulted by the formation of new types of active centers,possibly by coordination of external donor to certain positions on the catalyst.
The composition distribution (CD) and microisotacticity distribution (ID) of propene/1-hexene copolymer synthesized by MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) weredetermined by fractionating the copolymers according to crystallinity and characterizingthe fractions by 13CNMR. The effects of two alkoxysilane donors, triethoxyphenylsilane(PTES) and dimethoxydi-tert-butylsilane (TBMS), on CD and ID of the copolymrs werecompared. Three main parts in the CD diagram of each copolymer were distinguished,which were correlated to active center distribution (ACD) based on three groups of different active centers.By studying the changes in 1-hexene content,microisotacticity and reactivity ratio product of three typical fractions,the effects of external donor on ACD were better elucidated.It was found that TBMS shows much stronger effects on ACD than PTES.In the former system,most fractions were produced on active centers with relatively lower r1 r2,higher reactivity to 1-hexene,and higher stereospecificity as compared to the system without external donor.It is concluded that the observed very extensive changes in ACD are mainly resulted by the formation of new types of active centers,possibly by coordination of external donor to certain positions on the catalyst.
1997, 15(3): 226-230
Abstract:
The effect of different kinds of comonomers with or without flexible chain on proper-ties of copolyesters, such as transition temperature, crystallization velocity, crystallinityand size of crystallites, is studied. The experimental results indicate the obvious differ-ence in properties between comonomers with iso- and ortho-structure of phenyl ring andcomonomers with flexible chain. The influence of chemical structure of comonomers onproperties of copolyesters is discussed.
The effect of different kinds of comonomers with or without flexible chain on proper-ties of copolyesters, such as transition temperature, crystallization velocity, crystallinityand size of crystallites, is studied. The experimental results indicate the obvious differ-ence in properties between comonomers with iso- and ortho-structure of phenyl ring andcomonomers with flexible chain. The influence of chemical structure of comonomers onproperties of copolyesters is discussed.
1997, 15(3): 231-235
Abstract:
A copolymer of bismaleimide-diallylbisphenol A-diphenylsilandiol was synthesized andthe copolymerization was studied by using N-phenylmaleimide, bisphenol A and diphenyl-silandiol as model compounds. The copolymer could be well cured around 200℃, andthe cured resins had good thermal stability In the range of 170-210℃, a higher curingtemperature was favorable to obtain more thermal stable resin by reducing the content ofdiphenylsilandiol cyclo-homopolymer in resin which would spoil its thermal stability.
A copolymer of bismaleimide-diallylbisphenol A-diphenylsilandiol was synthesized andthe copolymerization was studied by using N-phenylmaleimide, bisphenol A and diphenyl-silandiol as model compounds. The copolymer could be well cured around 200℃, andthe cured resins had good thermal stability In the range of 170-210℃, a higher curingtemperature was favorable to obtain more thermal stable resin by reducing the content ofdiphenylsilandiol cyclo-homopolymer in resin which would spoil its thermal stability.
1997, 15(3): 236-241
Abstract:
A series of acrylonitrile (AN) copolymers with methyl acrylate (MA) or ethyl acrylate(EA) as comonomer (5--23 wt%) was prepared by free-radical copolymerization. The per-meability coefficients of the copolymers to oxygen and carbon dioxide were measured at1.0 MPa and at 30℃, and those to water vapor also measured at 100% relative humidityand at 30℃. All the AN/acrylic copolymers are semicrystalline. As the acrylate contentincrease, the permeability coefficients of the copolymers to oxygen and carbon dioxide are increased progressively,but those to water vapor are decreased progressively.The gas permeability coefficients of the polymers were correlated with free-volume fractions or the ratio of free volume to cohesive energy.
A series of acrylonitrile (AN) copolymers with methyl acrylate (MA) or ethyl acrylate(EA) as comonomer (5--23 wt%) was prepared by free-radical copolymerization. The per-meability coefficients of the copolymers to oxygen and carbon dioxide were measured at1.0 MPa and at 30℃, and those to water vapor also measured at 100% relative humidityand at 30℃. All the AN/acrylic copolymers are semicrystalline. As the acrylate contentincrease, the permeability coefficients of the copolymers to oxygen and carbon dioxide are increased progressively,but those to water vapor are decreased progressively.The gas permeability coefficients of the polymers were correlated with free-volume fractions or the ratio of free volume to cohesive energy.
1997, 15(3): 242-247
Abstract:
A polyacrylate/polyurethane (P(A) / P(U)) composite coating has been prepared bycrosslinking an acetoacetylated polyacrylate with a vinylic group terminated polyurethaneat room temperature. A model Michael reaction between ethyl acetoacetate (EAA) andmethyl acrylate (MA) was designed to study the crosslinking mechanism. It was foundthat the two active hydrogen atoms in acetoacetyl group can both add to vinylic groupsand the yield of mono- and bis-adducts are much affected by the molar ratio of acetoacetyl to vinylic groups.Higher crosslinking degree and better properties could be obtained with decreasing the molar ratio of the two active groups from 1/1 to 0.6/1 in the composite coatings.
A polyacrylate/polyurethane (P(A) / P(U)) composite coating has been prepared bycrosslinking an acetoacetylated polyacrylate with a vinylic group terminated polyurethaneat room temperature. A model Michael reaction between ethyl acetoacetate (EAA) andmethyl acrylate (MA) was designed to study the crosslinking mechanism. It was foundthat the two active hydrogen atoms in acetoacetyl group can both add to vinylic groupsand the yield of mono- and bis-adducts are much affected by the molar ratio of acetoacetyl to vinylic groups.Higher crosslinking degree and better properties could be obtained with decreasing the molar ratio of the two active groups from 1/1 to 0.6/1 in the composite coatings.
1997, 15(3): 248-253
Abstract:
A series of ethylene-norbornene copolymers were synthesised using VO (OEt) Cl2/Al2Et3Cl3 catalytic system and their structure was characterized by 1H-NMR, 1H-1HCOSY NMR and 13C-NMR. Assignments of NMR spectra were given and discussed indetail.
A series of ethylene-norbornene copolymers were synthesised using VO (OEt) Cl2/Al2Et3Cl3 catalytic system and their structure was characterized by 1H-NMR, 1H-1HCOSY NMR and 13C-NMR. Assignments of NMR spectra were given and discussed indetail.
1997, 15(3): 254-261
Abstract:
Acrylamide polymerization initiated with a redox initiation system consisting of cericion and ethyl N, N-diethyldithiocarbamyl acetate (EDCA) has been studied. It was foundthat the polymerization rate equation is in good agrement with that of a redox initiatedpolymerization, and the overall activation energy of the polymerization was determinedto be 25.2kJ·mol-1. Accordingly, the system belongs to a redox initiator. The initiationmechanism was proposed based on the end group analysis using FT-IR, UV spectroscopies.Analysis results revealed that the N,N-diethyldithiocarbamyl radical produced from the redox reaction of EDCA with ceric ion can initiate acrylonitrile (AN) polymerization and form the end group on PAN.The resulting PAN was photopolymerized with butyl acrylate (BA) to form PAN-b-PBA block copolymer.
Acrylamide polymerization initiated with a redox initiation system consisting of cericion and ethyl N, N-diethyldithiocarbamyl acetate (EDCA) has been studied. It was foundthat the polymerization rate equation is in good agrement with that of a redox initiatedpolymerization, and the overall activation energy of the polymerization was determinedto be 25.2kJ·mol-1. Accordingly, the system belongs to a redox initiator. The initiationmechanism was proposed based on the end group analysis using FT-IR, UV spectroscopies.Analysis results revealed that the N,N-diethyldithiocarbamyl radical produced from the redox reaction of EDCA with ceric ion can initiate acrylonitrile (AN) polymerization and form the end group on PAN.The resulting PAN was photopolymerized with butyl acrylate (BA) to form PAN-b-PBA block copolymer.
RING OPENING COPOLYMERIZATION OF SUCCINIC ANHYDRIDE-ETHYLENE OXIDE BY Al(Ⅲ) ORGANOMETALLIC CATALYSTS
1997, 15(3): 262-272
Abstract:
Ring opening copolymerization of succinic anhydride (SA) with ethylene oxide (EO)was successfully carried out by using a series of aluminum-based catalyst in 1,4-dioxane at62±2℃. The results showed that in-situ AlR3-H2O (R=ethyl, iso-butyl) catalysts gavehigher molecular weight (Mw～104), while Al(OR)3 catalysts gave the higher alternatingcopolymer structure with slightly lower molecular weight. The in-situ AlR3-H2O systems have been evaluated in more detail for the reaction which showed the optimum H2O/Al molar ratio to be 0.5.The copolymers with different composition (FSA/FEO=36/64 to 45/55 mol/mol) were synthesized by using different monomer feed ratio.The melting point(Tm),glass transition temperature(Tg) and enthalpy of fusion (△Hf) of these copolymers are depended on the copolymer composition and in the range of 87～102℃,-12～-18℃,and 37～66J/g,respectively.The second heating scan of DSC also indicated that the higher alternating copolymer was more easily recrystallized.The onset decomposition temperature was more than 300℃ under nitrogen and influenced by the copolymer composition.
Ring opening copolymerization of succinic anhydride (SA) with ethylene oxide (EO)was successfully carried out by using a series of aluminum-based catalyst in 1,4-dioxane at62±2℃. The results showed that in-situ AlR3-H2O (R=ethyl, iso-butyl) catalysts gavehigher molecular weight (Mw～104), while Al(OR)3 catalysts gave the higher alternatingcopolymer structure with slightly lower molecular weight. The in-situ AlR3-H2O systems have been evaluated in more detail for the reaction which showed the optimum H2O/Al molar ratio to be 0.5.The copolymers with different composition (FSA/FEO=36/64 to 45/55 mol/mol) were synthesized by using different monomer feed ratio.The melting point(Tm),glass transition temperature(Tg) and enthalpy of fusion (△Hf) of these copolymers are depended on the copolymer composition and in the range of 87～102℃,-12～-18℃,and 37～66J/g,respectively.The second heating scan of DSC also indicated that the higher alternating copolymer was more easily recrystallized.The onset decomposition temperature was more than 300℃ under nitrogen and influenced by the copolymer composition.
1997, 15(3): 273-281
Abstract:
Polymer strands with various draw ratios of a thermotropic liquid crystalline polymer(LCP) and modified poly(phenylene oxide) were prepared by drawing the melts leaving aslit die in open air. The morphology, structure and mechanical properties of the resultingstrands were studied as a function of LCP content and draw ratio. It was found that thethermal and mechanical properties of the matrix phase did not change dramatically withthe amount of LCP and draw ratio, but the orientation of LCP phase could be increased with draw ratio.The mechanical properties of the strands could be improved by moderately drawing the melts.Wide angle X-ray diffraction suggested that the improvement in tensile strength of the strands was due to the resyltant fibrillation of LCP phase and enhanced molecular orientation.Morpholohical observation indicated that excessive drawing of the strands could lead to the break down of the microfibrils of LCP and thus resulted in the dcrease of mechanical strength.
Polymer strands with various draw ratios of a thermotropic liquid crystalline polymer(LCP) and modified poly(phenylene oxide) were prepared by drawing the melts leaving aslit die in open air. The morphology, structure and mechanical properties of the resultingstrands were studied as a function of LCP content and draw ratio. It was found that thethermal and mechanical properties of the matrix phase did not change dramatically withthe amount of LCP and draw ratio, but the orientation of LCP phase could be increased with draw ratio.The mechanical properties of the strands could be improved by moderately drawing the melts.Wide angle X-ray diffraction suggested that the improvement in tensile strength of the strands was due to the resyltant fibrillation of LCP phase and enhanced molecular orientation.Morpholohical observation indicated that excessive drawing of the strands could lead to the break down of the microfibrils of LCP and thus resulted in the dcrease of mechanical strength.
1997, 15(3): 282-288
Abstract:
Cationic ring-opening copolymerization of 1, 4-anhydro-2, 3-O-isopropylidene-α-D-ribo-pyranose (AIRP) with 1,4-anhydro-2,3-di-O-benzyl-α-D-ribopyranose (ADBR) preparedfrom D-ribose was studied. Copolymerization using SbCl5 or BF3 OEt2 as catalyst atlow temperature gave stereoregular (1→4)β-D-ribofuranan (C-1 and C-4 ring cleavagesee Scheme 1) or (1→5) α-D-ribofuranan (C-1 and C-5 ring cleavage) respectively. Theeffects of catalysts, reaction time and temperatures on yield and stereoregularity of the ob-tained polymers were studied.Polymers were charaterized by molecular weight,1H NMR,13C NMR and optical rotation.
Cationic ring-opening copolymerization of 1, 4-anhydro-2, 3-O-isopropylidene-α-D-ribo-pyranose (AIRP) with 1,4-anhydro-2,3-di-O-benzyl-α-D-ribopyranose (ADBR) preparedfrom D-ribose was studied. Copolymerization using SbCl5 or BF3 OEt2 as catalyst atlow temperature gave stereoregular (1→4)β-D-ribofuranan (C-1 and C-4 ring cleavagesee Scheme 1) or (1→5) α-D-ribofuranan (C-1 and C-5 ring cleavage) respectively. Theeffects of catalysts, reaction time and temperatures on yield and stereoregularity of the ob-tained polymers were studied.Polymers were charaterized by molecular weight,1H NMR,13C NMR and optical rotation.
