蚕丝的接枝共聚反应动力学及其接枝结构

在真丝与DMAAm（N,N’-二甲基丙烯酰胺）的接枝共聚合反应中，分别加入两种RAFT（可逆加成-断裂-转移）试剂，RAFT试剂与源自引发剂分解的自由基进行链转移反应，生成新的齐聚物自由基。研究发现，RAFT-ST3试剂断裂生成的PAA-PST*（聚丙烯酸-聚苯乙烯）自由基提高了接枝共聚合反应速率，真丝接枝率和单体接枝效率；RAFT-AA30试剂断裂生成的PST-PAA*自由基对接枝共聚合反应动力学无影响。FT-IR（傅里叶红外光谱）分析表明，RAFT试剂及其衍生物并未与真丝共价键链接，接枝率仍由PDMAAm接枝链贡献。SEM（扫描电镜）显示，与常规接枝真丝相比，RAFT反应提高了纤维表面接枝聚合物分布的均匀性。

Graft copolymerization dinetics of silk and its grafting structure

Two kinds of RAFT (Reversible addition-fragmentation chain transfer) agents were introduced to mediate graft copolymerizations of silk fibers with DMAAm (N, N'-dimethyl acrylamide). New oligomer radicals generated from the chain transfer reactions between RAFT agents and propagation radicals. The RAFT-ST3 released an oligomer radical of PAA-PST* (polyacrylic acid-b-polystyrene), which accelerated graft copolymerization and caused increased silk grafting yield and monomer grafting efficiency. However, the kinetic was little influenced by the oligomer radical originated from RAFT-AA30 agent and had a chain structure of PST-PAA*. FT-IR (Fourier transform infrared spectroscopy) spectra showed that, RAFT agents and their derivatives did not covalently bond with silk fibers. The grafting yield was still contributed by the grafted PDMAAm chains. SEM (scanning electron microscope) analysis showed that, compared with conventional silk graft copolymerization (without RAFT agent), RAFT agents mediated reaction produced silk fibers with grafted PDMAAm chains distributing much more evenly on the outer surface.