tBCPMA: a new trifunctional acrylic monomer for convenient synthesis of a well-defined amphiphilic graft copolymer by successive RDRP

Abstract

A series of well-defined amphiphilic graft copolymers, consisting of a hydrophobic poly(tert-butyl acrylate) backbone and hydrophilic poly(N-isopropylacrylamide) side chains, were synthesized by successive reversible addition–fragmentation chain transfer (RAFT) polymerization and supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) in the presence of Cu(0). A new Cl-containing acrylate monomer, tert-butyl 2-((2-chloropropanoyloxy)methyl)acrylate, was first RAFT homopolymerized in a controlled way to give a well-defined homopolymer with a narrow molecular weight distribution (M_w/M_n = 1.10). This homopolymer directly initiated SARA ATRP of N-isopropylacrylamide to afford well-defined poly(tert-butyl acrylate)-g-poly(N-isopropylacrylamide) (PtBA-g-PNIPAM) graft copolymers (M_w/M_n ≤ 1.30) via the grafting—from a strategy without polymeric functionality transformation to introduce the initiating group. Finally, the hydrophobic PtBA backbone was selectively hydrolyzed in an acidic environment without affecting PNIPAM side chains to provide poly(acrylic acid)-g-poly(N-isopropylacrylamide) (PAA-g-PNIPAM) graft copolymers. The influences of the length of PNIPAM side chains and the salinity on the critical micelle concentration of the PtBA-g-PNIPAM amphiphilic graft copolymer were examined by fluorescence spectroscopy. Furthermore, thermo-responsive behaviors of the copolymers were investigated by UV-vis spectroscopy, dynamic light scattering, and transmission electron microscopy.