A ^(13)C-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 ...A ^(13)C-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 differentsites.展开更多
L-lactic acid (L-LA) based copolymer/hydroxylation vermiculites composites (PLLA-co-bis A/HVMTs) were prepared by in situ reaction among L-LA, adipic acid, and hydroxylation lamellar vermiculites (HVMTs) using bisphen...L-lactic acid (L-LA) based copolymer/hydroxylation vermiculites composites (PLLA-co-bis A/HVMTs) were prepared by in situ reaction among L-LA, adipic acid, and hydroxylation lamellar vermiculites (HVMTs) using bisphenol-A epoxy resin as chain extending agent. HVMTs were obtained by sulfuric acid-leaching of lamellar vermiculites (VMTs). The effects of sulfuric acid leaching on the VMTs structure were characterized by X-ray diffraction (XRD), 29Si magic-angle spinning nuclear magnetic resonance(29Si NMR), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). FTIR, FE-SEM, and TGA were used to characterize the reaction activity of HVMTs. The results indicated that VMTs with increased hydroxyl groups had been successfully obtained and could react with -COOH of the reaction system. The amount of L-LA based copolymer grafted on the surface of HVMTs was more than 22%. The onset decomposition temperature of L-LA based copolymer grafted on the surface of HVMTs was 30℃ higher than that of free L-LA based copolymer.展开更多
A new stable salen Schiff base cobalt and crown ether sodium complex （SalCo-NaB18C6） was prepared through copolymerization. This copolymer complex was applied to catalytic oxidation of hydrocarbon compound with mole...A new stable salen Schiff base cobalt and crown ether sodium complex （SalCo-NaB18C6） was prepared through copolymerization. This copolymer complex was applied to catalytic oxidation of hydrocarbon compound with molecular oxygen without reductant, which was shown the higher activity and selectivity for ketone, and reused effectively.展开更多
From the self-assembly of the typical Salen-type Schiff-base ligand H2L and Zn（OAc）2.2H20 in the molar ratio of 1：1 or 1：2, the mononuclear [Zn（L）（H2O）] （1） or binuclear [Zn2（L）（OAc）2（H2O）] （2） are o...From the self-assembly of the typical Salen-type Schiff-base ligand H2L and Zn（OAc）2.2H20 in the molar ratio of 1：1 or 1：2, the mononuclear [Zn（L）（H2O）] （1） or binuclear [Zn2（L）（OAc）2（H2O）] （2） are obtained, respectively. For both complexes 1 and 2, the unsaturated five-coordinate coordination environment to the catalytic active centers （Zn2＋ ions） permits the monomer insertion for the effective solution copolymerization of cyclohexene oxide and maleic anhydride. All the solution copolymerizations afford poly（ester-co-ether）s, while lower catalyst and co-catalyst concentrations are helpful for the formation of alternating polyester. Of the three co-catalysts, 4-（dimethylamino）pyridine is found to be the most efficient, while an excess thereof is detrimental for chain growth of the copolymers.展开更多
PVP, a synthetic polymer and chitosan, a natural polymer are biocompatible and have presented a great variety of interesting properties for cosmetic, biomedical, pharmaceutical and biotechnological applications, Many ...PVP, a synthetic polymer and chitosan, a natural polymer are biocompatible and have presented a great variety of interesting properties for cosmetic, biomedical, pharmaceutical and biotechnological applications, Many alternatives to improve the polymer propeties has been made as bleeding polymers, for example. In this work, two different techniques of hydrogel attainment were used: one from mixtures of acid aqueous cosolutions of chitosan and PVP, whose resultant films and solutions were irradiated, afterwards, by ultraviolet radiation (λ = 254 nm), another one from the reaction of poly (N-vinyl-2-pyrrolidone-co-acrolein)-a novel copolymer synthesized in our biomaterials laboratory-and chitosan. In the first one alternatives it was possible produce hydrogels directly from mixtures of aqueous acidic co-solutions of both polymers. In the second one, the attainment of hydrogels from Schiff base has proved to be an effective methodology for the production of hydrogels, showing good values of gel content and swelling.展开更多
基金This work was supported by the National Natural Science Foundation of China
文摘A ^(13)C-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 differentsites.
基金National High-Tech Research and Development Program of China ( 863 Program ) ( No. 2007AA03Z336) Program for New Century Excellent Talents in University,China ( No. NCET-07-0174) +1 种基金National Natural Science Foundations of China ( No. 21074021,No.50673018) The Fundamental Research Funds for the Central Universities ( No. 2011D10543)
文摘L-lactic acid (L-LA) based copolymer/hydroxylation vermiculites composites (PLLA-co-bis A/HVMTs) were prepared by in situ reaction among L-LA, adipic acid, and hydroxylation lamellar vermiculites (HVMTs) using bisphenol-A epoxy resin as chain extending agent. HVMTs were obtained by sulfuric acid-leaching of lamellar vermiculites (VMTs). The effects of sulfuric acid leaching on the VMTs structure were characterized by X-ray diffraction (XRD), 29Si magic-angle spinning nuclear magnetic resonance(29Si NMR), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). FTIR, FE-SEM, and TGA were used to characterize the reaction activity of HVMTs. The results indicated that VMTs with increased hydroxyl groups had been successfully obtained and could react with -COOH of the reaction system. The amount of L-LA based copolymer grafted on the surface of HVMTs was more than 22%. The onset decomposition temperature of L-LA based copolymer grafted on the surface of HVMTs was 30℃ higher than that of free L-LA based copolymer.
基金the National Natural Science Foundation of China （No.20274034）.
文摘A new stable salen Schiff base cobalt and crown ether sodium complex （SalCo-NaB18C6） was prepared through copolymerization. This copolymer complex was applied to catalytic oxidation of hydrocarbon compound with molecular oxygen without reductant, which was shown the higher activity and selectivity for ketone, and reused effectively.
基金financially supported by the National Natural Science Foundation of China(Nos.91222201,21173165 and 20871098)the Program for New Century Excellent Talents in Universities from the Ministry of Education of China(No.NCET-10-0936)+4 种基金the State Key Laboratory of Structure Chemistry(20100014)the Provincial Natural Foundation(2011JQ2011) of Shaanxithe Education Committee Foundation of Shaanxi Province(11JK0588,12JK0577)Graduate Innovation and Creativity Fund(YZZ12038) of Northwest UniversityHong Kong Research Grants Council(HKBU 202407 and FRG/06-07/II-16)
文摘From the self-assembly of the typical Salen-type Schiff-base ligand H2L and Zn（OAc）2.2H20 in the molar ratio of 1：1 or 1：2, the mononuclear [Zn（L）（H2O）] （1） or binuclear [Zn2（L）（OAc）2（H2O）] （2） are obtained, respectively. For both complexes 1 and 2, the unsaturated five-coordinate coordination environment to the catalytic active centers （Zn2＋ ions） permits the monomer insertion for the effective solution copolymerization of cyclohexene oxide and maleic anhydride. All the solution copolymerizations afford poly（ester-co-ether）s, while lower catalyst and co-catalyst concentrations are helpful for the formation of alternating polyester. Of the three co-catalysts, 4-（dimethylamino）pyridine is found to be the most efficient, while an excess thereof is detrimental for chain growth of the copolymers.
基金the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo e FAPESP and the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico e CNPq,for financial support
文摘PVP, a synthetic polymer and chitosan, a natural polymer are biocompatible and have presented a great variety of interesting properties for cosmetic, biomedical, pharmaceutical and biotechnological applications, Many alternatives to improve the polymer propeties has been made as bleeding polymers, for example. In this work, two different techniques of hydrogel attainment were used: one from mixtures of acid aqueous cosolutions of chitosan and PVP, whose resultant films and solutions were irradiated, afterwards, by ultraviolet radiation (λ = 254 nm), another one from the reaction of poly (N-vinyl-2-pyrrolidone-co-acrolein)-a novel copolymer synthesized in our biomaterials laboratory-and chitosan. In the first one alternatives it was possible produce hydrogels directly from mixtures of aqueous acidic co-solutions of both polymers. In the second one, the attainment of hydrogels from Schiff base has proved to be an effective methodology for the production of hydrogels, showing good values of gel content and swelling.
文摘采用先酯化后共聚的方法合成聚羧酸系减水剂,考察以甲基丙烯酸(MMA)和甲氧基聚乙二醇(MPEG)为原料酯化合成大单体甲氧基聚乙二醇甲基丙烯酸酯(MPEGMA)过程中阻聚剂对苯二酚用量、酸醇摩尔比、反应温度等对酯化率的影响.以大单体MPEGMA与马来酸酐、MMA和2-丙烯酰胺基-2-甲基丙烷磺酸共聚合成聚羧酸类减水剂,考察减水剂合成过程中MPEG相对分子质量和引发剂过硫酸铵用量以及减水剂掺量对减水剂性能的影响.结果表明:阻聚剂质量分数为0.4%、酸醇摩尔比为1.5∶1、反应温度为120℃时,酯化率可达到92.3%.当MPEG相对分子质量为1 000、引发剂的质量分数为5%,合成的减水剂掺量质量分数为0.3%时,水泥的净浆流动度可达281 mm.
