Synthesis of multifunctional ABC stars with a reduction-labile arm by consecutive ROP, RAFT and ATRP processes

摘要: This study aims at versatile synthesis of 3-arm ABC-type (A=poly( e -caprolactone), PCL; B=poly( N -isopropylacrylamide), PNIPAM; C=poly( tert -butyl acrylate), P t BA, or poly(acrylic acid), PAA) miktoarm star copolymers with a reducible disulfide linkage. Using 2-((2-((2-hydroxymethyl-2-((2-bromo-2-methyl)propionyloxy)methyl)propionyloxy)ethyl)disulfanyl)ethyl 4-cyano-4-(phenylcarbonothioylthio)pentanoate (HBCP) as heterotrifunctional initiator, consecutive ring-opening polymerization (ROP) -caprolactone (CL), reversible addition-fragmentation chain transfer (RAFT) -isopropy-lacrylamide (NIPAM) and atom radical (ATRP) acrylate ( BA) afforded ABC1 star, followed by subsequent hydrolysis to give ABC2 star. 1H nuclear magnetic resonance (1H NMR) gel permeation chromatography (GPC) analyses revealed the desired stars their precursors had well-controlled molecular weight relatively low polydispersity (PDI￡1.12). As confirmed GPC analysis, linkage in could be efficiently cleaved upon reductive stimulus, during which topology was converted from terpolymer mixtures homopolymer (B) diblock copolymer (AC1). In addition acting nanocarriers for stimuli-triggered drug delivery systems, ABC terminal bromide, dithiobenzoate hydroxyl functionalities are expected form other reduction-cleavable multicomponent such (BC- graft -A) m dendritic via postpolymerization modification. Our research affords straightforward “core-first” method construct multifunctional terpolymers stimuli-responsive arms reduction-labile