活性正离子聚合及原位制备聚醋酸乙烯酯-g-聚四氢呋喃共聚物/纳米银复合材料

通过将烯丙基溴/高氯酸银引发体系引发四氢呋喃活性正离子开环聚合与"grafting onto"合成方法相结合,原位制备了不同接枝密度和接枝链长度的新型聚醋酸乙烯酯-g-聚四氢呋喃接枝共聚物(PVAc-g-PTHF)及其与纳米银(Ag)的复合材料.采用傅里叶变换红外光谱(FTIR)、核磁共振波谱(1H-NMR)和多角度激光光散射-黏度-凝胶渗透色谱仪(MALLS-VIS-GPC)分别表征了该接枝共聚物的化学结构、共聚组成、分子量、分子量分布、接枝支链数目及支化度,采用原子力显微镜(AFM)、示差扫描量热分析(DSC)、偏光显微镜(POM)研究了接枝共聚物中接枝支链数目及支链长度对其微观形态、单端受限链段结晶行为的影响,并探讨了该纳米复合材料的抗菌性能.结果表明:所制备的不同支链数目和支链长度的PVAc-g-PTHF/Ag纳米复合材料,均表现出良好的抗菌性能;接枝共聚物PVAc-g-PTHF的重均分子量可达4.52×10~5,分子分子量较窄(M_w/M_n~1.8),支化因子可达0.19.接枝共聚物PVAc-g-PTHF可形成明显的相分离结构,其微观形态与接枝支链数目有关;相比相同分子量的双端不受限的PTHF链,PVAc-g-PTHF接枝共聚物中单端受限PTHF支链的结晶速率明显降低;在确定接枝支链数目的情况下,随着支链中PTHF链段长度增加,其结晶逐渐增强,结晶熔融温度及熔融焓均稍有增加.

Synthesis and Characterization of Poly(vinyl acetate)-g-polytetrahydrofuran Graft Copolymer with Silver Nanoparticles via Combination of Living Cationic Polymerization and Grafting-onto Approach

Poly(vinyl acetate)-g-polytetrahydrofuran graft copolymer with silver (Ag) nanoparticles,PVAc-g-PTHF/Ag,could be in situ prepared via combination of living cationic opening polymerization of tetrahydrofuran (THF) with allylBr/AgClO4 initiating system at 0 ℃ with "grafting onto" synthetic approach.Fourier transform infrared spectroscopy (FTIR),nuclear magnetic resonance (1H-NMR) and multi-angle laser light scattering-gel permeation chromatography (MALLS-GPC) were used to characterize the chemical structure,absolute weight-average molecular weight (Mw),molecular weight distribution (Mw/Mn) and branching degree (g') of the resulting PVAc-g-PTHF graft copolymers.The micromorphology and crystallization behavior of the branched PTHF segments were investigated by atomic force microscope (AFM),differential scanning calorimetry (DSC) and polarization microscopy (POM).The effect of the number of PTHF branches (Nb,PTHF) and number-average molecular weight (Mn,PTHF) of the PTHF branches on the micromorphology and crystallization rate of the resulting PVAc-g-PTHF graft copolymers was also investigated.The PVAc-g-PTHF graft copolymer with very high Mw of 4.52 × 105,relatively narrow molecular weight distribution (Mw/Mn ～ 1.8) and high branching degree of 0.19 was achieved.The Mw of the PVAc-g-PTHF graft copolymers increased remarkably with increases in both Nb,PTHF and Mn,PTHF of the PTHF branches.The glass transition temperature of PVAc backbone (Tg,PVAc) in the PVAc-g-PTHF graft copolymers increased with increasing Mn,PTHF of the PTHF branches by keeping the grafting density constant.The obvious phase separation was formed from the PVAc-g-PTHF graft copolymers and the micromorphology was dependent on the copolymer composition and Nb,PTHF of the PTHF branches by keeping Mn,PTHF of the PTHF branches or branching chain length unchanged.Compared to the unconfined free PTHF macromolecules,the crystallization rate of PTHF branches in the PVAc-g-PTHF graft copolymer was sharply decreased by setting the molecular weights of PTHF segments at the same.The crystallization rate of PTHF segments was increased by increasing the molecular weights of PTHF segments.However,the molecular weight of PTHF presented less effect on its crystallization rate of PTHF branches in PVAc-g-PTHF graft copolymers than that in the unconfined free PTHF homopolymers.Both the melting point of crystalline from PTHF segments and the melting enthalpy of PTHF crystalline increased slightly with increasing Mn,PTHF of the PTHF branches.Moreover,All the resulting PVAc-g-PTHF graft copolymer with different numbers of PTHF branches and different branching lengths or molecular weights of PTHF branches with silver (Ag) nanoparticles show good antibacterial property,suggesting their potential applications in biological and medical fields.