Preparation and properties of amphiphilic AB2 Y-shaped poly(styrene)-poly(N-isopropylacrylamide)2 copolymers through selective amidation and Michael additions reactions

Amphiphilic AB2 Y-shaped poly(styrene)-poly(N-isopropylacryamide)2 block copolymer (PS-(PNIPAAm)2) is prepared through selective amidation and Michael additions reactions, using ω-amino PS and ω-amino PNIPAAm chains as arms and 5-maleimidoisophthalic acid (MIPA) as a core. The first step is end-capping PS chains with MIPA via the Michael addition reaction between the amino groups of ω-amino PS and the maleimide group of MIPA. Incorporation of two PNIPAAm chains to PS-MIPA chain ends via amidation reaction between the amino groups of ω-amino PNIPAAm and the carboxylic acid groups of PS-MIPA result in amphiphilic AB2 Y-shaped PS-(PNIPAAm)2 block copolymer. The amphiphilic PS-(PNIPAAm)2 block copolymer forms nanoparticles in aqueous solution, which exhibit a temperature-responsive characteristic due to the presence of PNIPAAm chains. The applications of the polymeric nanoparticles as fluorophore carriers and fluorescent sensors are also studied.