Adsorption of poly(N-isopropylacrylamide-co-4-vinylpyridine) onto core–shell poly(styrene-co-methylacrylic acid) microspheres

Adsorption of the thermoresponsive copolymer of poly(N-isopropylacrylamide-co-4-vinylpyridine) (PNIPAM-co-P4VP) onto the core–shell microspheres of poly(styrene-co-methylacrylic acid) (PS-co-PMAA) is studied. The core–shell PS-co-PMAA microspheres are synthesized by one-stage soap-free polymerization in water. The copolymer of PNIPAM-co-P4VP is synthesized by free radical polymerization of N-isopropylacrylamide and 4-vinylpyridine in the mixture of DMF and water using K2S2O8 as initiator. Adsorption of PNIPAM-co-P4VP onto the core–shell PS-co-PMAA microspheres results in formation of the composite microspheres of PS/PMAA–P4VP/PNIPAM. The driven force to adsorb the copolymer of P4VP-co-PNIPAM onto the core–shell PS-co-PMAA microspheres is ascribed to hydrogen-bonding and electrostatic affinity between the P4VP and PMAA segments. The resultant composite microspheres of PS/PMAA–P4VP/PNIPAM with surface chains of PNIPAM are thermoresponsive in water and show a cloud-point temperature at about 33 °C.