Effects of branches on the crystallization kinetics of polypropylene-g-polystyrene （PP-g-PS） and polypropylene-g- poly（n-butyl acrylate） （PP-g-PnBA） graft copolymers with well-defined molecular structures were s...Effects of branches on the crystallization kinetics of polypropylene-g-polystyrene （PP-g-PS） and polypropylene-g- poly（n-butyl acrylate） （PP-g-PnBA） graft copolymers with well-defined molecular structures were systematically investigated by DSC. The Avrami equation was used to analyze the isothermal crystallization process, while the analysis of nonisothermal crystallization process was based on the Jeziorny-modified Avrami model and Mo model. The kinetics results of isothermal and nonisothermal crystallization verified the peculiar effects of branches on the crystallization process of PP backbones in PP-g-PS and PP-g-PnBA graft copolymers： on one hand, the interaction between branches （n-n interaction between PS branches, or dipole-dipole interaction between PnBA branches） restrained the mobility and reptation ability of the PP backbones, which hindered the crystallization process; on the other hand, the heterogeneous nucleation effect resulting from the branched structure and fluctuation-assisted nucleation mechanism （caused by microphase separation between the PS or PnBA rich phase and the PP rich phase） became more pronounced with increasing branch length, which facilitated the crystallization process.展开更多
Supercritical carbon dioxide （scCO2） was used as a reaction medium in synthesizing amphiphilic graft copolymers composed of poly（styrene-co-maleic anhydride） （SMA） backbones and methoxyl poly（ethylene glycol） ...Supercritical carbon dioxide （scCO2） was used as a reaction medium in synthesizing amphiphilic graft copolymers composed of poly（styrene-co-maleic anhydride） （SMA） backbones and methoxyl poly（ethylene glycol） （MPEG） side chains via esterification. The synthesized copolymers were characterized by Fourier transform infrared spectroscopy （FTIR）, gel permeation chromatography （GPC）, IH-NMR, thermo-gravimetric analysis （TGA） and differential scanning calorimetric analysis （DSC）. The gelation phenomenon was suppressed effectively by tuning reaction conditions. The influences of scCO2 temperature and pressure on the conversion of anhydride were investigated. It was found that the highest conversion ratio occurred at 80~C under a constant pressure of 14 MPa or 26 MPa. With the increase of scCO2 pressure, the conversion ratio increased first, and then leveled off. The conversion ratio of anhydride could be controlled by regulating the reaction conditions. It was also revealed that using low molecular weight MPEG brought a high conversion ratio of anhydride.展开更多
基金financially supported by the National Natural Science Foundation of China for the projects(Nos.51233005 and 51073149)
文摘Effects of branches on the crystallization kinetics of polypropylene-g-polystyrene （PP-g-PS） and polypropylene-g- poly（n-butyl acrylate） （PP-g-PnBA） graft copolymers with well-defined molecular structures were systematically investigated by DSC. The Avrami equation was used to analyze the isothermal crystallization process, while the analysis of nonisothermal crystallization process was based on the Jeziorny-modified Avrami model and Mo model. The kinetics results of isothermal and nonisothermal crystallization verified the peculiar effects of branches on the crystallization process of PP backbones in PP-g-PS and PP-g-PnBA graft copolymers： on one hand, the interaction between branches （n-n interaction between PS branches, or dipole-dipole interaction between PnBA branches） restrained the mobility and reptation ability of the PP backbones, which hindered the crystallization process; on the other hand, the heterogeneous nucleation effect resulting from the branched structure and fluctuation-assisted nucleation mechanism （caused by microphase separation between the PS or PnBA rich phase and the PP rich phase） became more pronounced with increasing branch length, which facilitated the crystallization process.
基金financially supported by the 973 Program of China(No.2009CB623402)the Fundamental Research Funds for the Central Universities(MOE Engineering Research Center of Membrane and Water Treatment Technology, Grant no.KYJD09011)+1 种基金the 863 Program of China(No.2009AA062902)Zhejiang Provincial Sci & Tech Plan of China(No.2010C31028)
文摘Supercritical carbon dioxide （scCO2） was used as a reaction medium in synthesizing amphiphilic graft copolymers composed of poly（styrene-co-maleic anhydride） （SMA） backbones and methoxyl poly（ethylene glycol） （MPEG） side chains via esterification. The synthesized copolymers were characterized by Fourier transform infrared spectroscopy （FTIR）, gel permeation chromatography （GPC）, IH-NMR, thermo-gravimetric analysis （TGA） and differential scanning calorimetric analysis （DSC）. The gelation phenomenon was suppressed effectively by tuning reaction conditions. The influences of scCO2 temperature and pressure on the conversion of anhydride were investigated. It was found that the highest conversion ratio occurred at 80~C under a constant pressure of 14 MPa or 26 MPa. With the increase of scCO2 pressure, the conversion ratio increased first, and then leveled off. The conversion ratio of anhydride could be controlled by regulating the reaction conditions. It was also revealed that using low molecular weight MPEG brought a high conversion ratio of anhydride.
