A series of water-soluble multi-responsive miktoarm star polymers (MAS)

in which poly(oligo(ethylene oxide) acrylate-co-di(ethylene oxide) ethyl ether acrylate) P(OEGA-co-DEGA) and poly(2-dimethylaminoethyl acrylate) (PDMAEA) served as the thermoresponsive and pH-responsive building blocks

have been successively prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization using the arm-first approach.Firstly

P(OEGA-co-DEGA) and PDMAEA were prepared via RAFT technique to give well-dened linear trithiocarbonate terminated macro-RAFT agents.Then the two preformed linear macro-RAFT agents were cross-linked by a disulde crosslinker N

N'-double acryloyl cystamine (BAC) to give the desired multi-responsive (temperature

pH and redox) star polymers.The structure and composition of the resultant polymers were characterized by the FTIR and 1H-NMR

the molecule weight and molecular weight distribution of the polymers were obtained by GPC.Besides

DLS and UV-Vis were used to investigate the lower critical solution temperature (LCST) of the polymers in aqueous solutions.The results show that this method can obtain narrow polydispersity star polymers (PDI 1.3) and the polymers exhibit reversible thermal-induced volume phase transition and pH responsibility.The LCST of the star polymers in aqueous solutions could be tuned by changing the feed ratio of the arms or the pH values.For example

the LCST of the star polymer as determined to be 38.2 ℃ when the molar feed ratio of P(OEGA-co-DEGA) and PDMAEA was 5 :5 and the polymer concentration was 1 mg/mL.