Poly(N-isopropylacrylamide) branched polymer nanoparticles

A series of thermally responsive branched copolymers based on N-isopropylacrylamide (NIPAAm) and poly(ethylene glycol) methacrylate (PEGMA) are synthesized using a direct, single step modified free radical polymerization strategy. The aqueous solution behaviour and nanoparticle formation of these copolymers are studied and correlated to the NIPAAm : PEGMA molar ratio and PEGMA chain length. All copolymers are water-soluble as discrete polymer chains at low temperature. On raising the solution temperature, inter-polymer interactions-that is, aggregation of polymers-are inhibited at higher PEGMA molar ratios and at long PEGMA chain lengths. The statistical incorporation of monomer residues and the short primary chain lengths within these branched copolymer structures result in the effective dampening out of NIPAAm thermo-responsivity and provides new insight into the architecture and composition of these complex copolymer structures.