原子转移自由基聚合法合成大豆分离蛋白-g-聚甲基丙烯酸2-羟乙酯

GRAFT POLYMERIZATION OF 2-HYDROXYETHYL METHACRYLATE ON SOY PROTEIN ISOLATE via ATOM TRANSFER RADICAL POLYMERIZATION

通过酰胺化反应在大豆分离蛋白(SPI)表面引入溴原子,合成了大分子引发剂SPI-Br,以CuCl和bpy为催化体系,通过原子转移自由基聚合法(ATRP)合成了大豆分离蛋白-g-聚甲基丙烯酸2-羟乙酯(SPI-g-PHEMA).用FTIR1、3C-NMR、GPC对大分子引发剂、接枝产物和接枝物降解链进行结构表征.结果表明,得到了表面接枝聚甲基丙烯酸2-羟乙酯长链的大豆分离蛋白接枝聚合物,用紫外分光光度计(UV)、荧光分光光度计z、eta电位和透射电镜(TEM)表征了接枝产物的溶液性质和微观形态.

The synthesis of poly（2-hydroxylthyl methacrylate） grafted soy protein isolates （SPI-g-PHEMA） using atom transfer radical polymerization （ATRP） was described. Poly（2-hydroxyethyl methacrylate） （PHEMA） is one of most extensively studied biocompatible polymer, which has been used for applications such as contact lenses. The scheme of the work was that the soy protein isolate macroinitiator （SPI-Br） was synthesized first by condensation reaction of the active amino groups and 2-bromoisobutyryl bromide, and the resulting secondary bromide could be used as initiator for HEMA monomer in atom transfer radical polymerization to propare SPI-g-PHEMA. FTIR and 13 C-NMR spectra confirmed the conversion from SPI sequence to SPI-Br. Atom transfer radical polymerization of 2-hydroxyethyl methacrylate （HEMA） on SPI was carried out in aqueous solutions using SPI-Br as initiator, copper chloride/bipyridine （CuCl/bpy） as catalyst. FTIR spectrum was used to characterize the successful polymerization of HEMA onto SPI globulin. The graft chain was cleaved from SPI-g- PHEMA by degradation of hydrochloric acid for purpose of the measurement of molecular weight of graft chain by GPC. The changes in the spectra of SPI, SPI-Br,SPI-g-PHEMA and grafted chain confirmed successive steps in the synthesis of SPI-g-PHEMA hybrids. A series of comparative experiments were taken with different reaction mediums （H2 O, H2 O/n-propanol, n-propanol）, and higher molecular weight result was gained in aqueous solutions by ATRP. The number average molecular weight was about 1.16 × 10^4, and a polydispersity was about 1.12, so the water medium system was chosen for further study. The molecule weight and the polydispersity of graft chain cleaved from SPI-g-PHEMA prepared via ATRP initiated by soy protein isolate macroinitiator were similar to those of PHEMA prepared by normal ATRP using 2-bromoisobutyryl bromide without SPI in solution under similar reaction conditions. The solution properties of SPI-g-PHEMA were characterized by UV and fluorescent spectrophotometer. The results indicated that with increasing of pH value, the solubility of SP1 and SPI-g-PHEMA increased, and the hydrophobicity decreased. The zeta-potential of SPI and SPI-g-PHEMA solutions were also studied by zetapotentiometer. The static charges on the surface of SPI molecules increased clearly after graft modification, and the values of the zeta potential of SPI and SPI-g-PHEMA solutions decreased with the increase of pH values. The TEM images showed that the diameter of SPI-g-PHEMA was beyond that of SPI, and the morphologies of SPI and SPI-g- PHEMA were different.