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1999 Volume 17 Issue 5
1999, 17(5): 411-415
Abstract:
Photocuring of new dental resins composed of tri(2-hydroxyethyl) isocyanurate triacrylate (THITA)alone and its mixtures with trimethylolpropane triacrylate (TMPTA) or pentaerythritol triacrylate (PETA)initiated by camphorquinone/amine system was studied by photocalorimetry. Among several different aminesas coinitiators, 2-ethyl-4-dimethylaminobenzoate (AM-3), N,N-dimethylbenzylamine (AM-5) and 2,4,6-[tri-(dimethylaminomethyl)] phenol (AM-6) are most effective. Upon irradiation, photopolymerization can occur immediately and no induction period appears in N2 nor in air.Comparing the THITA/TMPTA and THITA/PETA mixtures,the parameters of photopolymerization and hardness of photocured samples show a small difference and only change slightly with varying molar ratios of mixture.In the presence of inorganic filler,the hardness of photocuring resins is almost the same as that for commercial products.
Photocuring of new dental resins composed of tri(2-hydroxyethyl) isocyanurate triacrylate (THITA)alone and its mixtures with trimethylolpropane triacrylate (TMPTA) or pentaerythritol triacrylate (PETA)initiated by camphorquinone/amine system was studied by photocalorimetry. Among several different aminesas coinitiators, 2-ethyl-4-dimethylaminobenzoate (AM-3), N,N-dimethylbenzylamine (AM-5) and 2,4,6-[tri-(dimethylaminomethyl)] phenol (AM-6) are most effective. Upon irradiation, photopolymerization can occur immediately and no induction period appears in N2 nor in air.Comparing the THITA/TMPTA and THITA/PETA mixtures,the parameters of photopolymerization and hardness of photocured samples show a small difference and only change slightly with varying molar ratios of mixture.In the presence of inorganic filler,the hardness of photocuring resins is almost the same as that for commercial products.
1999, 17(5): 417-422
Abstract:
By covalently binding chromophore NPP, N-(4-nitrophenyl)-(L)-prolinol, to a structurallycontrolled cage-like cross-linking polymer (SCCP), a modified nonlinear optical (NLO) polymeric filmprepared by "in situ poling and sol-gel" process successfully overcame the fundamental problem of NPPchromophores subliming out from the cages of the "doped" NLO polymeric film when heated or placed underUV light. Its d33 (coefficient of second harmonic generation) is 2.0×10-8 esu. measured by IR dichroism. The modified film has a low decay of the SHG signal and preserves 94% of the initial value after 50 days at room temperature.These properties match that of the "doped"film,indicating that the modified film also retains the main advantages of the "doped" film.
By covalently binding chromophore NPP, N-(4-nitrophenyl)-(L)-prolinol, to a structurallycontrolled cage-like cross-linking polymer (SCCP), a modified nonlinear optical (NLO) polymeric filmprepared by "in situ poling and sol-gel" process successfully overcame the fundamental problem of NPPchromophores subliming out from the cages of the "doped" NLO polymeric film when heated or placed underUV light. Its d33 (coefficient of second harmonic generation) is 2.0×10-8 esu. measured by IR dichroism. The modified film has a low decay of the SHG signal and preserves 94% of the initial value after 50 days at room temperature.These properties match that of the "doped"film,indicating that the modified film also retains the main advantages of the "doped" film.
1999, 17(5): 423-427
Abstract:
A novel type of polysoap hydrogel based on poly(tetraethylenepentamine-epichlorohydrin)hydrophobically modified by stearic acid was prepared. The deswelling behaviors of polysoap hydrogels werestudied by immersing the gels in buffer solution at various pHs and ionic species. The deswelling of the gelsdid not depend on the cationic species of electrolyte but depended strongly on the anionic species. Acomparison of polysoap gels with the gel unmodified hydrophobically verified the importance of hydrophobic interaction,which enhances the occurrence of deswelling rate.
A novel type of polysoap hydrogel based on poly(tetraethylenepentamine-epichlorohydrin)hydrophobically modified by stearic acid was prepared. The deswelling behaviors of polysoap hydrogels werestudied by immersing the gels in buffer solution at various pHs and ionic species. The deswelling of the gelsdid not depend on the cationic species of electrolyte but depended strongly on the anionic species. Acomparison of polysoap gels with the gel unmodified hydrophobically verified the importance of hydrophobic interaction,which enhances the occurrence of deswelling rate.
1999, 17(5): 429-433
Abstract:
MQ silicone resins were prepared through hydrolytic condensation of ethyl polysilicate ortetraethoxysilane and hexamethyl disiloxane. The unit ratio of the MQ resins was determined by 29Si-NMR.The relationship of the unit ratio of the product resins with that in the feed was studied. When the reactionwas catalyzed by aqueous hydrochloric acid, and the unit ratio of M to Q in the feed was more than 1, the unitratio of the product was usually lower than that of the feed. The MQ silicon with an unit ratio of M/Q>2 could not be obtained.However if the reaction was catalyzed by concentrated sulfuric acid and the reverse hydrolysis process was employed,MQ silicone resin with very high M/Q ratio was successfully prepared.
MQ silicone resins were prepared through hydrolytic condensation of ethyl polysilicate ortetraethoxysilane and hexamethyl disiloxane. The unit ratio of the MQ resins was determined by 29Si-NMR.The relationship of the unit ratio of the product resins with that in the feed was studied. When the reactionwas catalyzed by aqueous hydrochloric acid, and the unit ratio of M to Q in the feed was more than 1, the unitratio of the product was usually lower than that of the feed. The MQ silicon with an unit ratio of M/Q>2 could not be obtained.However if the reaction was catalyzed by concentrated sulfuric acid and the reverse hydrolysis process was employed,MQ silicone resin with very high M/Q ratio was successfully prepared.
1999, 17(5): 435-440
Abstract:
An interpenetrating polymer networks (IPN) consisting of an epoxy-based polymer network and apolymethyl methacrylate network were synthesized and characterized. The IPN showed only one Tg, andhence a homogeneous-phase morphology was suggested. The second-order nonlinear optical coefficient (d33)of the IPN was measured to be 1.72×10-7 esu. The study of NLO temporal stability at room temperature andelevated temperature (100℃) indicated that the IPN exhibits a high stability in the dipole orientation due to the permanent entanglements of two component networks in the IPN system.Long-term stability of second harmonic coefficients was observed at room temperature for more than 1000h.
An interpenetrating polymer networks (IPN) consisting of an epoxy-based polymer network and apolymethyl methacrylate network were synthesized and characterized. The IPN showed only one Tg, andhence a homogeneous-phase morphology was suggested. The second-order nonlinear optical coefficient (d33)of the IPN was measured to be 1.72×10-7 esu. The study of NLO temporal stability at room temperature andelevated temperature (100℃) indicated that the IPN exhibits a high stability in the dipole orientation due to the permanent entanglements of two component networks in the IPN system.Long-term stability of second harmonic coefficients was observed at room temperature for more than 1000h.
1999, 17(5): 441-446
Abstract:
Two polysiloxanes with pendant fullerene moieties and their platinum or rhodium complexes havebeen prepared from C60 via amination with ω-decenylamine, followed by hydrosilylation with triethoxysilaneand immobilization on fumed silica or by hydrosilylation with methyldichlorosilane and polycondensationwith polydimethylsiloxanol, and then by reacting them with potassium chloroplatinite or rhodium chloride inacetone respectively under argon atmosphere. It was found that the four noble metal complexes are effective catalysts for the hydrosilylation of olefins with triethoxysilane.The regioselectivity of platinum complexes for styrene increases remarkably by introducing C60 moiety.Factors influencing catalytic actalytic activity and the mechanism have been investigated.
Two polysiloxanes with pendant fullerene moieties and their platinum or rhodium complexes havebeen prepared from C60 via amination with ω-decenylamine, followed by hydrosilylation with triethoxysilaneand immobilization on fumed silica or by hydrosilylation with methyldichlorosilane and polycondensationwith polydimethylsiloxanol, and then by reacting them with potassium chloroplatinite or rhodium chloride inacetone respectively under argon atmosphere. It was found that the four noble metal complexes are effective catalysts for the hydrosilylation of olefins with triethoxysilane.The regioselectivity of platinum complexes for styrene increases remarkably by introducing C60 moiety.Factors influencing catalytic actalytic activity and the mechanism have been investigated.
1999, 17(5): 447-452
Abstract:
A series of liquid crystalline multi-block copolymers poly [1,6-bis(4-oxybenzoyl-oxy)hexaneterephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segment lengths were synthesizedin tetrachloroethane by solution polycondensation in which hydroxyl terminated PC and acyl chlorideterminated PHTH-6 were used. It is found that block copolymers with high molecular weight and well-defined structures were obtained. All the block copolymers exhibit a nematic liquid crystalline texture.
A series of liquid crystalline multi-block copolymers poly [1,6-bis(4-oxybenzoyl-oxy)hexaneterephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segment lengths were synthesizedin tetrachloroethane by solution polycondensation in which hydroxyl terminated PC and acyl chlorideterminated PHTH-6 were used. It is found that block copolymers with high molecular weight and well-defined structures were obtained. All the block copolymers exhibit a nematic liquid crystalline texture.
1999, 17(5): 453-458
Abstract:
Liquid crystalline multi-block copolymers poly [1,6-bis(4-oxybenzoyl-oxy)hexane terephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segments of polycarbonate (PC) and thermotropicpolyester PHTH-6 were synthesized in tetrachloroethane at 144～146℃, The influence of segment length onthe resulting phase structure and thermal behavior of block copolymers was also discussed. It is demonstratedby TEM and DMA that the resulting block copolymers show a considerable microphase separation. The degree of phase separation and the thermal behavior of the block copolymers are strongly dependent on the molecular weight of the segments incorporated.
Liquid crystalline multi-block copolymers poly [1,6-bis(4-oxybenzoyl-oxy)hexane terephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segments of polycarbonate (PC) and thermotropicpolyester PHTH-6 were synthesized in tetrachloroethane at 144～146℃, The influence of segment length onthe resulting phase structure and thermal behavior of block copolymers was also discussed. It is demonstratedby TEM and DMA that the resulting block copolymers show a considerable microphase separation. The degree of phase separation and the thermal behavior of the block copolymers are strongly dependent on the molecular weight of the segments incorporated.
1999, 17(5): 459-464
Abstract:
Cationic polymerizations of 1,3-pentadiene (PD) initiated by trimethylsilyl chloride (TMSCl) incombination with TiCl4 were carried out in n-hexane at 30℃. The yield of polymer was greatly increased bythe addition of TMSCl, indicating that the TMSCl/TiCl4 combination is an efficient initiating system for PDcationic polymerization. However, the introduction of TMSCl gave rise to a drop in the molecular weight ofthe polymer. Kinetic results demonstrated that the polymerization initiated by TMSCl/TiCl4 is 4.5 times faster than that induced by TiCl4 alone.Various ethers were used to mediate the TMSCl/TiCl4 initiating system.Adding diphenyl ether could increase both the yield and molecular weight of the polymer.Structural evidence illustrates that the polymerization is indeed initiated by TiCl4 in combination with HCl resulting from bydrolysis by adventitious water.
Cationic polymerizations of 1,3-pentadiene (PD) initiated by trimethylsilyl chloride (TMSCl) incombination with TiCl4 were carried out in n-hexane at 30℃. The yield of polymer was greatly increased bythe addition of TMSCl, indicating that the TMSCl/TiCl4 combination is an efficient initiating system for PDcationic polymerization. However, the introduction of TMSCl gave rise to a drop in the molecular weight ofthe polymer. Kinetic results demonstrated that the polymerization initiated by TMSCl/TiCl4 is 4.5 times faster than that induced by TiCl4 alone.Various ethers were used to mediate the TMSCl/TiCl4 initiating system.Adding diphenyl ether could increase both the yield and molecular weight of the polymer.Structural evidence illustrates that the polymerization is indeed initiated by TiCl4 in combination with HCl resulting from bydrolysis by adventitious water.
1999, 17(5): 465-470
Abstract:
The photosensitive system which can initiate methyl methacrylate with visible light was composedof compound 1 bis(η-5-cyclopentadienyl)-bis[2,6-difluoro-3-(1-H-pyrrolyl)phenyl]titanium (titanocene) andcompound 2 [(3,3'-carbonylbis(7-diethylamino coumarin)] (ketocoumarin dye). The high photosensitiveinitiating efficiency of this photosensitive system could be very promising for efficient system for laser (Ar+488 nm) to plate and photocuring for thick coating and ink. The variation of UV-visible spectrum of compound 2 during irradiation indicates that photolysis of compound 2 is through its triplet state and it can be quenched by O2.The much quicker photobleaching of the photosensitive system suggests that there exists certain quick electron transfer reaction between compounds 1 and 2.
The photosensitive system which can initiate methyl methacrylate with visible light was composedof compound 1 bis(η-5-cyclopentadienyl)-bis[2,6-difluoro-3-(1-H-pyrrolyl)phenyl]titanium (titanocene) andcompound 2 [(3,3'-carbonylbis(7-diethylamino coumarin)] (ketocoumarin dye). The high photosensitiveinitiating efficiency of this photosensitive system could be very promising for efficient system for laser (Ar+488 nm) to plate and photocuring for thick coating and ink. The variation of UV-visible spectrum of compound 2 during irradiation indicates that photolysis of compound 2 is through its triplet state and it can be quenched by O2.The much quicker photobleaching of the photosensitive system suggests that there exists certain quick electron transfer reaction between compounds 1 and 2.
1999, 17(5): 471-475
Abstract:
Five neutral macromolecular polyester gadolinium (Ⅲ) complexes with pendant hydrophobic alkyland aromatic functional groups were prepared. The longitudinal relaxation rates of these complexes weremeasured. One of these Gd (Ⅲ) complexes was chosen for the acute toxicity test and T1-weighted imagingmeasurement. Preliminary results showed that. compared with Gd-DTPA. the neutral macromoleculargadolinium (Ⅲ) complexes provide higher T1 relaxivity enhancement and longer function duration.
Five neutral macromolecular polyester gadolinium (Ⅲ) complexes with pendant hydrophobic alkyland aromatic functional groups were prepared. The longitudinal relaxation rates of these complexes weremeasured. One of these Gd (Ⅲ) complexes was chosen for the acute toxicity test and T1-weighted imagingmeasurement. Preliminary results showed that. compared with Gd-DTPA. the neutral macromoleculargadolinium (Ⅲ) complexes provide higher T1 relaxivity enhancement and longer function duration.
1999, 17(5): 476-481
Abstract:
Two new unbridged zirconocenes, bis(2,4,7-trimethyl indenyl)zirconium dichloride (Met-Ⅰ) andbis(2-methyl-4,7-diethyl indenyl)zirconium dichloride (Met-Ⅱ) were prepared in order to investigate thesteric effects of substituents on the nature of the catalysts for the polymerization of propylene. A mixture ofmethyl aluminoxane (MAO) and triisobutylaluminum [Al(iBu)3] was used as cocatalyst to activate thesecatalysts. The decrease in steric bulkiness of substituents at 4 and 7 positions of the indenyl ring resulted in an increase of both activity and molecular weight as well as the isotacticity.
Two new unbridged zirconocenes, bis(2,4,7-trimethyl indenyl)zirconium dichloride (Met-Ⅰ) andbis(2-methyl-4,7-diethyl indenyl)zirconium dichloride (Met-Ⅱ) were prepared in order to investigate thesteric effects of substituents on the nature of the catalysts for the polymerization of propylene. A mixture ofmethyl aluminoxane (MAO) and triisobutylaluminum [Al(iBu)3] was used as cocatalyst to activate thesecatalysts. The decrease in steric bulkiness of substituents at 4 and 7 positions of the indenyl ring resulted in an increase of both activity and molecular weight as well as the isotacticity.
1999, 17(5): 483-490
Abstract:
A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-ray diffraction. It was realized that all the polymers have nematic thermotropic liquid crystallinecharacteristics. The melting temperature (Tm) and isotropization temperature (Ti) of the polymers change regularly with varying lengths of the alkoxy side group and the length of alkylene group in the main chain in company with an even-odd effect.The mesophase temperature range also varies regularly with the polymer structure.It is shown that the mesophase range has been widened.
A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-ray diffraction. It was realized that all the polymers have nematic thermotropic liquid crystallinecharacteristics. The melting temperature (Tm) and isotropization temperature (Ti) of the polymers change regularly with varying lengths of the alkoxy side group and the length of alkylene group in the main chain in company with an even-odd effect.The mesophase temperature range also varies regularly with the polymer structure.It is shown that the mesophase range has been widened.
1999, 17(5): 491-493
Abstract:
A novel soluble poly(aryl ether ketone) was prepared by the reaction of 4-(3-phenyl-4-hydr-oxyphenyl)phthalazinone with 4,4'-difluorobenzophenone. The polymer was characterized by DSC, TGA andX-ray diffraction.
A novel soluble poly(aryl ether ketone) was prepared by the reaction of 4-(3-phenyl-4-hydr-oxyphenyl)phthalazinone with 4,4'-difluorobenzophenone. The polymer was characterized by DSC, TGA andX-ray diffraction.
1999, 17(5): 495-497
Abstract:
A new poly(aryl ether ketone) containing biphenylphthalazinone moiety was prepared by thereaction of 4-(4-hydroxybiphenyl) phthalazine-1-one with 4, 4'-difluorobenzophenone. The monomer and thepolymer were characterized by FT-IR and 1H-NMR. Some properties of this polymer were described.
A new poly(aryl ether ketone) containing biphenylphthalazinone moiety was prepared by thereaction of 4-(4-hydroxybiphenyl) phthalazine-1-one with 4, 4'-difluorobenzophenone. The monomer and thepolymer were characterized by FT-IR and 1H-NMR. Some properties of this polymer were described.
1999, 17(5): 499-509
Abstract:
New liquid crystalline monomer, 2,5-bis[(4'-methoxyphenoxy)carbonyl]phenyl acrylate wassuccessfully synthesized. Polyacrylate with laterally attached mesogens via ester linkage was also derived.This polymer forms an enantiotropic liquid crystal phase while its monomer exhibits a metastable nematicphase with respect to the crystalline state. However, its liquid crystallinity is very low as compared to that ofpoly{2,5-bis[(4'-methoxyphenoxy)carbonyl]-styrene}.
New liquid crystalline monomer, 2,5-bis[(4'-methoxyphenoxy)carbonyl]phenyl acrylate wassuccessfully synthesized. Polyacrylate with laterally attached mesogens via ester linkage was also derived.This polymer forms an enantiotropic liquid crystal phase while its monomer exhibits a metastable nematicphase with respect to the crystalline state. However, its liquid crystallinity is very low as compared to that ofpoly{2,5-bis[(4'-methoxyphenoxy)carbonyl]-styrene}.
