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

Abstract

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

Synthesis and Star/Linear Topology Transformation of a Mechanically Linked ABC Terpolymer

“…Polymer topology has been recognized as a critical factor significantly influencing polymer properties in bulk and in solution among other factors including composition and molecular weight. − In fact, a variety of cyclic, star, dendritic, and interlocked polymers have been synthesized. In light of dynamic polymer structure control, the development of topology-transformable polymers which can change their topology in response to a particular stimulus, is attractive from the viewpoints of controlling polymer structure and properties, development of stimuli-responsive polymers, and so on. − …”

Synthesis of ABC Miktoarm Star Copolymers via Organocatalyzed Living Radical Polymerization

“…They are advanced branching architectures in polymer science and offer unique assembly structures that are useful for drug/gene delivery, for example 1–4. The synthetic approaches of ABC miktoarm stars include “core‐first,”5–8 “coupling‐onto,”9–13 “combinatorial,”14–26 and “iterative”27–29 approaches.…”

Synthesis and characterization of poly(styrene-b-methyl methacrylate) block copolymers via ATRP and RAFT

“…This is because linearity, low polydispersity and active polymer chain ends of the monomer increase the polymer conversion and molecular weight. (Liu, Tang et al 2015). The prediction of the structure in the synthesis of block copolymers is one of the important aspects of macromolecular chemistry.…”

“…This is because linearity, low polydispersity and active polymer chain ends of the monomer increase the polymer conversion and molecular weight. (Liu, Tang et al 2015).…”