Login In
2005 Volume 23 Issue 6
2005, 23(6): 567-591
Abstract:
Polycyclotrimerization and polycoupling of acetylenic monomers respectively furnish hyperbranched polyarylenes and polyynes with high molecular weights (up to 1 #61620; 106) in high yields (up to 99.9%). The polymers possess low intrinsic viscosities and high thermal stabilities, losing little of their weights when heated to 400℃. Upon pyrolysis at 800℃, the polymers graphitize with high char yields (up to 86%). Hyperbranched polyarylenes efficiently emit deep-blue to blue-green lights with fluorescence quantum yields up to 98% and strongly attenuate intense laser pulses with optical power-limiting performances superior to that of C60, a well-known optical limiter. Poly(alkenephenylenes), poly(aroylarylenes) and polyynes are readily cross-linkable by UV irradiation, serving as excellent photoresist materials for the generation of patterns with nanometer resolution. Thin films of hyperbranched polyynes exhibit very high refractive indexes (n up to 1.86). The internal and terminal acetylene moieties of the polyynes readily form complexes with cobalt carbonyls, which can be transformed into soft ferromagnetic ceramics with high magnetic susceptibilities (Ms up to ca.118 emu/g) and near-zero magnetic losses.
Polycyclotrimerization and polycoupling of acetylenic monomers respectively furnish hyperbranched polyarylenes and polyynes with high molecular weights (up to 1 #61620; 106) in high yields (up to 99.9%). The polymers possess low intrinsic viscosities and high thermal stabilities, losing little of their weights when heated to 400℃. Upon pyrolysis at 800℃, the polymers graphitize with high char yields (up to 86%). Hyperbranched polyarylenes efficiently emit deep-blue to blue-green lights with fluorescence quantum yields up to 98% and strongly attenuate intense laser pulses with optical power-limiting performances superior to that of C60, a well-known optical limiter. Poly(alkenephenylenes), poly(aroylarylenes) and polyynes are readily cross-linkable by UV irradiation, serving as excellent photoresist materials for the generation of patterns with nanometer resolution. Thin films of hyperbranched polyynes exhibit very high refractive indexes (n up to 1.86). The internal and terminal acetylene moieties of the polyynes readily form complexes with cobalt carbonyls, which can be transformed into soft ferromagnetic ceramics with high magnetic susceptibilities (Ms up to ca.118 emu/g) and near-zero magnetic losses.
2005, 23(6): 593-602
Abstract:
The studies of our group on the catalytic activities of rare earth calixarene complexes in polymer syntheses are reviewed. Rare earth calixarene complexes are effect catalysts for the polymerizations of butadiene, isoprene, ethylene, styrene, propylene oxide, styrene oxide, trimethylene carbonate and 2,2-dimethyl-trimethylene carbonate.
The studies of our group on the catalytic activities of rare earth calixarene complexes in polymer syntheses are reviewed. Rare earth calixarene complexes are effect catalysts for the polymerizations of butadiene, isoprene, ethylene, styrene, propylene oxide, styrene oxide, trimethylene carbonate and 2,2-dimethyl-trimethylene carbonate.
2005, 23(6): 603-610
Abstract:
The kinetics of melt grafting acrylic acid (AA) onto linear low density polyethylene (LLDPE) by using reactive extrusion was investigated. The polymeric peroxides (POOP and POOH) generated by electron beam irradiation were used to initiate the graft reaction. The samples taken out from the barrel at five ports along screw axis were analyzed by FTIR. The spectra show that both the graft copolymerization and homopolymerization proceed in two stages: the graft degree (or mass of homopolymer) increases linearly with the reaction time in the initial stage, and then gradually in the second stage. The rate of graft copolymerization Rg is always faster than that of homopolymerization Rh in the present system and the activation energy is 131 kJ•mol1 for graft copolymerization and 127 kJ•mol1 for homopolymeirzation. These results were interpreted in terms of solubility and diffusion of monomer, as well as the reactivity and the concentration of reactive species. The relationships between reaction rate and monomer concentration and peroxide concentration were found to be: Rg [M]1.46[POOP+POOH]0.53 and Rh [M]1.08[POOH]0.51, which indicate that the addition of monomer to polymeric radicals is a slow step for the graft copolymerization.
The kinetics of melt grafting acrylic acid (AA) onto linear low density polyethylene (LLDPE) by using reactive extrusion was investigated. The polymeric peroxides (POOP and POOH) generated by electron beam irradiation were used to initiate the graft reaction. The samples taken out from the barrel at five ports along screw axis were analyzed by FTIR. The spectra show that both the graft copolymerization and homopolymerization proceed in two stages: the graft degree (or mass of homopolymer) increases linearly with the reaction time in the initial stage, and then gradually in the second stage. The rate of graft copolymerization Rg is always faster than that of homopolymerization Rh in the present system and the activation energy is 131 kJ•mol1 for graft copolymerization and 127 kJ•mol1 for homopolymeirzation. These results were interpreted in terms of solubility and diffusion of monomer, as well as the reactivity and the concentration of reactive species. The relationships between reaction rate and monomer concentration and peroxide concentration were found to be: Rg [M]1.46[POOP+POOH]0.53 and Rh [M]1.08[POOH]0.51, which indicate that the addition of monomer to polymeric radicals is a slow step for the graft copolymerization.
2005, 23(6): 611-617
Abstract:
A novel silane coupling agent bearing sulfobetaine group, N,N-diethyl-N-(3-sulfopropyl)-aminopropyl- trimethoxysilane (DESATS), was first designed, synthesized and characterized. Its solution property was studied by means of dynamic light scattering. DESATS was successfully bonded onto the surface of the glass and proved by ESCA. Platelet adhesion assay in vitro indicated that the nonthrombogenicity of glass slide modified with DESATS is greatly improved.
A novel silane coupling agent bearing sulfobetaine group, N,N-diethyl-N-(3-sulfopropyl)-aminopropyl- trimethoxysilane (DESATS), was first designed, synthesized and characterized. Its solution property was studied by means of dynamic light scattering. DESATS was successfully bonded onto the surface of the glass and proved by ESCA. Platelet adhesion assay in vitro indicated that the nonthrombogenicity of glass slide modified with DESATS is greatly improved.
2005, 23(6): 619-626
Abstract:
A series of salicylaldimines, synthesized in high yield via microwave-assisted condensation of salicylaldehyde and 2-alkoxyaniline were allowed to react with nickel chloride to form six-coordinated nickel complexes. These nickel complexes were carefully characterized, and the solid structure of 1a was elucidated by X-Ray diffraction. Activated with MAO, the nickel complexes showed good activity for homopolymerization of norbornene. Reaction parameters, such as the ratio of nickel precursor to MAO, monomer concentration, reaction time and the reaction temperature, as well as the nature of the ligands were found to have significant effects on the catalytic activity and some properties of the resulting polynorbornene.
A series of salicylaldimines, synthesized in high yield via microwave-assisted condensation of salicylaldehyde and 2-alkoxyaniline were allowed to react with nickel chloride to form six-coordinated nickel complexes. These nickel complexes were carefully characterized, and the solid structure of 1a was elucidated by X-Ray diffraction. Activated with MAO, the nickel complexes showed good activity for homopolymerization of norbornene. Reaction parameters, such as the ratio of nickel precursor to MAO, monomer concentration, reaction time and the reaction temperature, as well as the nature of the ligands were found to have significant effects on the catalytic activity and some properties of the resulting polynorbornene.
2005, 23(6): 627-633
Abstract:
Propene/1-decene copolymers (P-co-D) were synthesized by means of slurry polymerization process under atmospheric pressure using Ziegler-Natta catalyst (MgCl2/TiCl4/AlEt3). The random P-co-Ds were elastic, low-crystalline, thermally stable and therefore suitable to be used as membrane materials in organophilic pervaporation with chloroform/water mixture. Its mechanical strength is better than polydimethylsiloxane (PDMS). The correlation between structural parameters (glass transition temperature and crystallinity) and properties of organophilic pervaporation were investigated.
Propene/1-decene copolymers (P-co-D) were synthesized by means of slurry polymerization process under atmospheric pressure using Ziegler-Natta catalyst (MgCl2/TiCl4/AlEt3). The random P-co-Ds were elastic, low-crystalline, thermally stable and therefore suitable to be used as membrane materials in organophilic pervaporation with chloroform/water mixture. Its mechanical strength is better than polydimethylsiloxane (PDMS). The correlation between structural parameters (glass transition temperature and crystallinity) and properties of organophilic pervaporation were investigated.
2005, 23(6): 635-642
Abstract:
In the UV-Vis spectra of pure light-scattering systems, there is an exponential relationship between absorbance and wavelength ( ). Here, the exponent n is named as flocculation-coagulation parameter. In the present paper, the effects of different additives on the stability of poly(N,N-methylenebisacrylamide-co-4-vinylpyridine) (poly(Bis-co-4-VP)) microgel dispersion were studied in detail via this parameter. The results showed that the stability of the dispersion mainly comes from the ionization of pyridine groups, making the microgel positively charged on its surface. This was confirmed by the measurement of Zeta potential and the result of conductometric titration. The result of fluorescence analysis indicated that the hydrophobicity in the microgels is enhanced with the increase in total 4-VP unit content.
In the UV-Vis spectra of pure light-scattering systems, there is an exponential relationship between absorbance and wavelength ( ). Here, the exponent n is named as flocculation-coagulation parameter. In the present paper, the effects of different additives on the stability of poly(N,N-methylenebisacrylamide-co-4-vinylpyridine) (poly(Bis-co-4-VP)) microgel dispersion were studied in detail via this parameter. The results showed that the stability of the dispersion mainly comes from the ionization of pyridine groups, making the microgel positively charged on its surface. This was confirmed by the measurement of Zeta potential and the result of conductometric titration. The result of fluorescence analysis indicated that the hydrophobicity in the microgels is enhanced with the increase in total 4-VP unit content.
2005, 23(6): 643-650
Abstract:
The effects of L-phenylalanine (L-Phe) on the synthesis of poly(N,N-methylenebisacrylamide-co-4-vinylpyridine) (poly(Bis-co-4-VP)) (micro)gels by -ray irradiation were studied. The addition of L-Phe could not only decrease the gelation dose (Dg) of the synthesis obviously, but also transform the morphology of copolymer from microgel to gel. In addition, the swelling ability of the (micro)gels was also affected in the presence of L-Phe. The decrease of Dg was ascribed to the effect of pH, while the transformation of the morphology was ascribed to the effect of L-Phe on the stability of the poly(Bis-co-4-VP) microgel. Such an effect was confirmed further as compared with the effects of L-alanine, L-glutamic acid, L-arginine, sulfuric acid and aqueous ammonia.
The effects of L-phenylalanine (L-Phe) on the synthesis of poly(N,N-methylenebisacrylamide-co-4-vinylpyridine) (poly(Bis-co-4-VP)) (micro)gels by -ray irradiation were studied. The addition of L-Phe could not only decrease the gelation dose (Dg) of the synthesis obviously, but also transform the morphology of copolymer from microgel to gel. In addition, the swelling ability of the (micro)gels was also affected in the presence of L-Phe. The decrease of Dg was ascribed to the effect of pH, while the transformation of the morphology was ascribed to the effect of L-Phe on the stability of the poly(Bis-co-4-VP) microgel. Such an effect was confirmed further as compared with the effects of L-alanine, L-glutamic acid, L-arginine, sulfuric acid and aqueous ammonia.
2005, 23(6): 651-656
Abstract:
A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared. The degree of functionalization with aldehyde groups is well suited for the subsequent use of the products as Wittig reagents. The polymer bound aldehyde was reacted with Wittig reagents to give olefin groups grafted on styrene-divinylbenzene copolymers. The reactions were carried out in phase transfer catalysis conditions. A simple procedure for the calculation of the degree of functionalization and the statistical modeling of the structural repetitive unit of the copolymer are reported.
A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared. The degree of functionalization with aldehyde groups is well suited for the subsequent use of the products as Wittig reagents. The polymer bound aldehyde was reacted with Wittig reagents to give olefin groups grafted on styrene-divinylbenzene copolymers. The reactions were carried out in phase transfer catalysis conditions. A simple procedure for the calculation of the degree of functionalization and the statistical modeling of the structural repetitive unit of the copolymer are reported.
2005, 23(6): 657-663
Abstract:
Isothermal crystallization process of polymers in a confined volume was simulated in the case of instantaneous nucleation by use of the Monte Carlo method. The influence of sample thickness on some kinetic parameters of crystallization was quantitatively evaluated. It was found that there was a critical thickness value. Influence of thickness on the crystallization behavior was only found for samples of thickness near and less than the critical value. For thick samples the Avrami plot showed straight lines with a turning point at the late stage of crystallization due to the secondary crystallization. When the thickness was near or less than the critical value a primary turning point appeared in the Avrami plot at the very beginning of the crystallization process. A model was proposed to explain the mechanism of this phenomenon. According to this model the critical thickness value is related to the nucleation density or the average distance between adjacent nuclei, and the primary turning point is an indication of a transformation of crystal growth geometry from a three-dimensional mode to a two-dimensional one. Analysis of experimental results of PEO isothermally crystallized at 53.5℃ was consistent with the proposed model.
Isothermal crystallization process of polymers in a confined volume was simulated in the case of instantaneous nucleation by use of the Monte Carlo method. The influence of sample thickness on some kinetic parameters of crystallization was quantitatively evaluated. It was found that there was a critical thickness value. Influence of thickness on the crystallization behavior was only found for samples of thickness near and less than the critical value. For thick samples the Avrami plot showed straight lines with a turning point at the late stage of crystallization due to the secondary crystallization. When the thickness was near or less than the critical value a primary turning point appeared in the Avrami plot at the very beginning of the crystallization process. A model was proposed to explain the mechanism of this phenomenon. According to this model the critical thickness value is related to the nucleation density or the average distance between adjacent nuclei, and the primary turning point is an indication of a transformation of crystal growth geometry from a three-dimensional mode to a two-dimensional one. Analysis of experimental results of PEO isothermally crystallized at 53.5℃ was consistent with the proposed model.
2005, 23(6): 665-669
Abstract:
A hyperbranched poly(aryleneethynylene) containing anthracene chromophore was synthesized by palladium-catalyzed cross-coupling reaction of 2,4,6-triiodophenyl 9-anthracenylcarboxylate with 9,9-bis[4-(2-propynyloxy)phenyl]-9H-fluorene. The structure and properties of the polymer are characterized and evaluated by NMR, IR, UV, PL and TGA analyses. The polymer is soluble in common organic solvents, possesses high thermal stability (Td > 330℃), and emits a strong blue light of 465 nm in both solution and solid states.
A hyperbranched poly(aryleneethynylene) containing anthracene chromophore was synthesized by palladium-catalyzed cross-coupling reaction of 2,4,6-triiodophenyl 9-anthracenylcarboxylate with 9,9-bis[4-(2-propynyloxy)phenyl]-9H-fluorene. The structure and properties of the polymer are characterized and evaluated by NMR, IR, UV, PL and TGA analyses. The polymer is soluble in common organic solvents, possesses high thermal stability (Td > 330℃), and emits a strong blue light of 465 nm in both solution and solid states.
2005, 23(6): 671-674
Abstract:
Rare-earth ternary catalysts Y(CCl3COO)3-ZnR2-glycerin were prepared for the copolymerization of carbon dioxide and propylene oxide (PO), where dialkylzincs (ZnR2) were diethylzinc, di(n-propyl)zinc, di(n-butyl)zinc, di(i-propyl)zinc, di(i-butyl)zinc, di(s-butyl)zinc, respectively. The Y(CCl3COO)3-ZnR2-glycerin catalysts displayed the highest catalytic activity at the molar ratio of Y(CCl3COO)3:ZnR2:glycerin = 1:20:10. In the same copolymerization condition, catalysts containing dialkylzincs with branched alkyl group showed lower catalytic activity than that with primary alkyl group. For those catalysts including dialkylzincs with primary alkyl group, their catalytic activity decreases with increasing number of carbon atom in the alkyl group with the following sequence: Y(CCl3COO)3-ZnEt2-glycerin > Y(CCl3COO)3-Zn(n-Pr)2-glycerin>Y(CCl3COO)3-Zn(n-Bu)2-glycerin. However, the alkyl group in the dialkylzinc does not influence the insertion of PO into the propagation chain end.
Rare-earth ternary catalysts Y(CCl3COO)3-ZnR2-glycerin were prepared for the copolymerization of carbon dioxide and propylene oxide (PO), where dialkylzincs (ZnR2) were diethylzinc, di(n-propyl)zinc, di(n-butyl)zinc, di(i-propyl)zinc, di(i-butyl)zinc, di(s-butyl)zinc, respectively. The Y(CCl3COO)3-ZnR2-glycerin catalysts displayed the highest catalytic activity at the molar ratio of Y(CCl3COO)3:ZnR2:glycerin = 1:20:10. In the same copolymerization condition, catalysts containing dialkylzincs with branched alkyl group showed lower catalytic activity than that with primary alkyl group. For those catalysts including dialkylzincs with primary alkyl group, their catalytic activity decreases with increasing number of carbon atom in the alkyl group with the following sequence: Y(CCl3COO)3-ZnEt2-glycerin > Y(CCl3COO)3-Zn(n-Pr)2-glycerin>Y(CCl3COO)3-Zn(n-Bu)2-glycerin. However, the alkyl group in the dialkylzinc does not influence the insertion of PO into the propagation chain end.
2005, 23(6): 675-679
Abstract:
The photoconductivities of a series of novel polyacetylene derivatives (PAs) serving as charge generation materials in the single-layered photoreceptors were investigated using photoinduced xerographic discharge technique. It was found that the substitution can improve the photosensitivity of PAs by increasing the conjugation of electrons. When the substituent is itself photoconductive, the photoconductivity becomes even higher. It can be concluded from cyclic voltammetry that when the HOMO level of the polymer is closer to that of the charge transport material, the photoconduction performance will be better.
The photoconductivities of a series of novel polyacetylene derivatives (PAs) serving as charge generation materials in the single-layered photoreceptors were investigated using photoinduced xerographic discharge technique. It was found that the substitution can improve the photosensitivity of PAs by increasing the conjugation of electrons. When the substituent is itself photoconductive, the photoconductivity becomes even higher. It can be concluded from cyclic voltammetry that when the HOMO level of the polymer is closer to that of the charge transport material, the photoconduction performance will be better.
2005, 23(6): 681-685
Abstract:
Poly(p-phenylene) (PPP) films have been electrochemically deposited on mirrorlike stainless steel (SS) electrode surfaces by direct oxidation of benzene in boron trifluoride diethyl etherate (BFEE) solutions at a constant applied potential of 1.7 V (versus Ag/AgCl). The chain conformations of as-grown PPP films have been studied by Raman spectroscopy. The results demonstrated that high synthesis temperature favors the formation of planar PPP, and the conformation of planar PPP can be changed into torsional PPP by cooling treatment.
Poly(p-phenylene) (PPP) films have been electrochemically deposited on mirrorlike stainless steel (SS) electrode surfaces by direct oxidation of benzene in boron trifluoride diethyl etherate (BFEE) solutions at a constant applied potential of 1.7 V (versus Ag/AgCl). The chain conformations of as-grown PPP films have been studied by Raman spectroscopy. The results demonstrated that high synthesis temperature favors the formation of planar PPP, and the conformation of planar PPP can be changed into torsional PPP by cooling treatment.
