Synthesis Of Star-shaped Copolymers With Four Arms Based On PCL

Controlled-radical polymerization (CRP) is a major field in polymer science and engineering. CRP is also known as "pseudoliving" radical polymerization. A polymerization process is considered to be living if the growing chains do not experience permanent termination and/or transfer during the course of polymerization. The current most effective and versatile CRP processes are (1) stable free-radical polymerization (SFRP), best represented by nitroxide-mediated polymerization (NMP), (2) metal-catalyzed atom-transfer radical polymerization (ATRP), and (3) reversible additionfragmentation chain transfer (RAFT) polymerization. With the development of CRP, combining the ionic polymerization, amphiphilic copolymer with complex architecture was designed and synthesised in past decades. some comb-like, star, dendritic or hyperbranchcopolymers are synthesized.1. A novel four arms star-shaped amphiphilic diblock copolymer PCL4-b-PAA4 and triblock copolymer PCL4-b-PAA4-b-PNIPAM4 were prepared by a combination of coordination-insertion ring-opening polymerization, atom transfer radical polymerization (ATRP). Firstly, the four-arm star-shaped poly(s-caprolactone) (PCL4) was carried out by coordination-insertion ring-opening polymerizationusing stannous octoate (Sn(Oct)2) as catalyst. Then, the star-shaped polymer (PCL4) was esterified by reaction with 2-bromoisobutyryl bromide, and then used as ATRP macroinitiator to initiate polymerization of poly(tert-butyl acrylate) to prepare PCL4-b-PtBA4. After hydrolysis of PtBA blocks, amphiphilic multiblock copolymer PCL4-b-PAA4 was obtained. Moreover, the obtained diblock copolymer PCL4-b-PtBA4 was used as ATRP macroinitiator to initiate polymerization of poly(N-isopropylacrylamide) (PNIPAM) prepare triblock copolymer PCL4-b-PAA4-b-PNIPAM4. The desired diblock and triblock copolymer and its intermediates were characterized by 1H NMR, IR and GPC in details.2. A novel four arms star-shaped amphiphilic triblock copolymer PCL4-b-PS4-b-PEO4 were prepared by a combination of coordination-insertion ring-opening polymerization, ATRP and Atom Transfer Nitroxide Radical Coupling (ATNRC). Firstly, the four-arm star-shaped PCL4 was carried out and was esterified by reaction with 2-bromoisobutyryl bromide, and then used as ATRP macroinitiator to initiate polymerization of polystyrene. And TEMPO-PEO was synthesized by means of living anionic polymerization of using 4-hydroxyl-2,2,6,6-tetramethylpiperidinyl-1-oxy (HTEMPO) and diphenylm ethyl-potassium (DPMK) as initiator. The TEMPO-PEO with the pending TEMPO groups was used to monitor the star-shaped copolymer PCL4-b-PS4. Thus, star copolymers with four arms of poly(ε-caprolactone)-b-polystyrene-b-poly(ethylene oxide) was obtained. The desired diblock and triblock copolymer and its intermediates were characterized by 1H NMR, IR and GPC in details.