Modification Of SEBS Rubber Via Living Radical Polymerization

In this thesis, iron-mediated atom-transfer radical polymerization using activators generated by electron transfer (AGET ATRP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization were used to modify commerically available polystyrene-b-poly(ethylene-co-1-butene)-b-polystyrene triblock copolymer (SEBS) rubber. The results are summarized as follows:(1) System I:Modification of SEBS rubber via iron-mediated AGET ATRP in the presence of limitied amounts of air. Chloromethylated SEBS (SEBS@CH2Cl) used as the macro ATRP initiator was obtained through Blanc chlormethylation reaction. Different kinds of grafted SEBSs were obtained using methyl methacrylate (MMA), styrene (St) and tert-butyl acrylate (tBA) as the monomers, FeCl3·6H2O as the catalyst, tris(3,6-dioxaheptyl)amine or triphenylphosphine as the ligand, and vitamin C as the reducing agent and tetrahydrofuran or toluene as the solvent. The grafting density could be adjusted by degree of chloromethylation of SEBS. The grafting kinetics of MMA was studied in detail. The composition and structures of the grafted copolymers were characterized by Fourier transform infrared (FT-IR) spectroscopy and 1H nuclear magnetic resonance (1H NMR). Thermogravimetric analysis (TGA) was used to inversigate the thermal property of the obtained triblock-graft copolymers.(2) System II:Modification of SEBS rubber via RAFT polymerization and electron-spun study of the modified SEBS. Macro-RAFT agent SEBS@BCBD with SEBS as R group and BCBD as Z group was synthesized by the reaction between SEBS@CH2Cl synthesized in system I and carbazole as well as carbon sulfide. Then RAFT polymerization of N-isopropylacrylamide (NIPAM) was carried out to synthesize the triblock-graft copolymer SEBS-g-PNIPAM with hydrophilic PNIPAM grafted chains. Fourier transform infrared (FT-IR) spectroscopy and 1H nuclear magnetic resonance (1H NMR) were used to confirm the successful synthesis of the SEBS@BCBD and SEBS-g-PNIPAM. At last, electro-spun fibers of SEBS obtained from an electrospinning unit were studied by scanning electron microscope (SEM).