The soluble poly(vinyl alcohol)-g-poly(ethylene glycol) monomethyl ether(PVA-g-MPEG) graft copolymer was prepared by two-step synthesis. The structure of the PVA-g-MPEG was characterized by 1H NMR. The phase change an...The soluble poly(vinyl alcohol)-g-poly(ethylene glycol) monomethyl ether(PVA-g-MPEG) graft copolymer was prepared by two-step synthesis. The structure of the PVA-g-MPEG was characterized by 1H NMR. The phase change and crystallization behavior were analyzed by DSC and POM. The phase change behavior presented solid-to-solid state; the phase transition process was reversible. Compared with pure MPEG, the phase change temperature and enthalpy of graft copolymer declined because of the addition of PVA. Due to the intermolecular interaction and chemical bond, the crystalline shape of the graft copolymer was changed.展开更多
Novel physically cross-linked hydrogels, composed of PVA and hydroxy-terminated polyamidoamine(PAMAM) dendrimer G6-OH, were prepared by cyclic freezing/thawing treatment of aqueous solutions containing PVA and G6-OH. ...Novel physically cross-linked hydrogels, composed of PVA and hydroxy-terminated polyamidoamine(PAMAM) dendrimer G6-OH, were prepared by cyclic freezing/thawing treatment of aqueous solutions containing PVA and G6-OH. FTIR analysis indicates that PAMAM dendrimer G6-OH was successfully introduced into PVA hydrogels. Higher contents of G6-OH in PVA/G6-OH hydrogels resulted in higher swelling ratios, and faster reswelling rates. With the increase of freezing/thawing cyclic times, the swelling ratios and reswelling rates of PVA/G6-OH hydrogels decreased, which is similar to that of physically cross-linked PVA hydrogel.展开更多
To obtain a novel support with practical value for metallocene catalyst(\%η\%\|C\-5H\-5)TiCl\-3(CpTiCl\-3), poly(styrene\|co\|4\|vinylpyridine)/SiO\-2 nanoscale hybrid material(SrP/SiO\-2) was firstly produced as sup...To obtain a novel support with practical value for metallocene catalyst(\%η\%\|C\-5H\-5)TiCl\-3(CpTiCl\-3), poly(styrene\|co\|4\|vinylpyridine)/SiO\-2 nanoscale hybrid material(SrP/SiO\-2) was firstly produced as support. After pretreatment by methylaluminoxane(MAO), the hybrid materials reacted with CpTiCl\-3. The results from SAXS, SEM and TEM indicated the morphology and structure of organic/inorganic hybrid materials, and the size of inorganic particle in hybrid was nanoscale. The results from IR and XPS showed that there were two possible cationic active species in the hybrid\|supported catalyst, the polymerization results of styrene proved this possibility.展开更多
文摘The soluble poly(vinyl alcohol)-g-poly(ethylene glycol) monomethyl ether(PVA-g-MPEG) graft copolymer was prepared by two-step synthesis. The structure of the PVA-g-MPEG was characterized by 1H NMR. The phase change and crystallization behavior were analyzed by DSC and POM. The phase change behavior presented solid-to-solid state; the phase transition process was reversible. Compared with pure MPEG, the phase change temperature and enthalpy of graft copolymer declined because of the addition of PVA. Due to the intermolecular interaction and chemical bond, the crystalline shape of the graft copolymer was changed.
文摘Novel physically cross-linked hydrogels, composed of PVA and hydroxy-terminated polyamidoamine(PAMAM) dendrimer G6-OH, were prepared by cyclic freezing/thawing treatment of aqueous solutions containing PVA and G6-OH. FTIR analysis indicates that PAMAM dendrimer G6-OH was successfully introduced into PVA hydrogels. Higher contents of G6-OH in PVA/G6-OH hydrogels resulted in higher swelling ratios, and faster reswelling rates. With the increase of freezing/thawing cyclic times, the swelling ratios and reswelling rates of PVA/G6-OH hydrogels decreased, which is similar to that of physically cross-linked PVA hydrogel.
文摘To obtain a novel support with practical value for metallocene catalyst(\%η\%\|C\-5H\-5)TiCl\-3(CpTiCl\-3), poly(styrene\|co\|4\|vinylpyridine)/SiO\-2 nanoscale hybrid material(SrP/SiO\-2) was firstly produced as support. After pretreatment by methylaluminoxane(MAO), the hybrid materials reacted with CpTiCl\-3. The results from SAXS, SEM and TEM indicated the morphology and structure of organic/inorganic hybrid materials, and the size of inorganic particle in hybrid was nanoscale. The results from IR and XPS showed that there were two possible cationic active species in the hybrid\|supported catalyst, the polymerization results of styrene proved this possibility.
