Synthesis Of Graft Copolymers By The Combination Of Living Anionic Polymerization And Ring Opening Polymerization Mechanism

Graft copolymers have great applications in the field of materials because of their tunable backbone and side chains. With the development of polymerization methodologies, chemists have synthesized various graft copolymers with specific structures by combining different polymerization mechanisms, such as atom transfer radical polymerization (ATRP), reversible addition fragmentation transfer polymerization (RAFT), living anionic polymerization (LAP), ring opening polymerization (ROP) or ring opening metathesis polymerization (ROMP). Generally, the design and synthesis of main chain is the key step in the process to graft copolymers. In this work, the graft copolymers with Poly(ethylene oxide) (PEO) or Poly(isoprene) (PI) backbone were realized by combination of LAP and ROP, and the "grafting onto" and "grafting from" strategies were also adopted. Detailed work is shown as following:1. For the graft polymers with PEO as main chain, firstly, taking ethylene glycol as initiator, diphenylmethylpotassium (DPMK) as deprotonated agent and triisobutylaluminum (i-Bu3Al) as catalyst, ring opening copolymerization of ethylene oxide and epichlorohydrin were operated to get Poly(epichlorohydrin-co-ethylene oxide) (Poly(ECH-co-EO)) with relatively high molecular weight and narrow dispersity. Then, the macroanions of Poly(isoprene) lithium (PI"Li+)、Poly(styrene) lithium (PS"Li+)、PI-b-PS-Li+ and PS-b-PI-Li+ were synthesized by LAP and capped with DPE agent, and the DPE-capped macroanions were further coupled with methyl chloride groups on Poly(ECH-co-EO) to get graft copolymers. In order to evaluate the effect of DPE on grafting efficiency(G.E.), the model polymers of Poly(ECH-co-EO)-Bu and Poly(ECH-co-EO)-DPE-Bu were designed and synthesized. The results showed that DPE could significantly improve the G.E. of graft copolymer at room temperature. Finally, all the intermediates and target products were characterized by GPC, NMR, FTIR. The thermal behaviors of graft copolymers were determined by DSC instruments, and the results showed that the glass transition temperature could be regularly tuned by changing the composition and molecular weight of side chains2. For the graft polymers with PI as main chain, firstly, the PI was obtained by LAP mechanism and peroxided into epoxide PI (EPI) with in situ peroxide system H2O2/HCOOH. Then, the epoxy groups on EPI were attacked by macroanions and graft copolymers PI-g-PI, PI-g-PS, PI-g-(PI-b-PS) and PI-g-(PS-b-PI) with one hydroxyl group at each grafting site were synthesized. Subsequently, using PI-g-PS as macroinitiator, DPMK as deprotonated agent, the ring opening polymerization of EO was realized to get graft polymer PI-g-PS/PEO. Finally, all the intermediates and target products were analyzed by GPC, NMR and FTIR. The thermal behaviors of graft polymers were observed by DSC instrument, and the results showed that both the melting and crystalline temperature would be higher with the increase of PEO content of graft polymersAlso, the self-assembly behavior of PI-g-PS/PEO in selective solvent were investigated by AFM and TEM instruments, and the "clover"-like and core-corona morphologies were observed from AFM images.