Thermoresponsive aggregation of PS–PNIPAM–PS triblock copolymer: A combined study of light scattering and small angle neutron scattering

Abstract

The aggregate structure of a thermoresponsive polystyrene–b-poly(N-isopropylacrylamide)–b-polystyrene (PS–PNIPAM–PS) triblock copolymer was investigated as a function of temperature in aqueous solutions by the combination of small angle neutron scattering (SANS) and dynamic/static light scattering (LS). SANS shows that the system consists of spherical intermicellar aggregates which self-assemble into larger clusters either at temperatures below or above the lower critical solution temperature (LCST). Upon the solubility transition of PNIPAM the mass of the clusters increases significantly, whereas their size remains constant and the size of the intermicellar aggregates decreases. This picture is consistent with the LS data where the signature of the two entities in solution is observed. The combination of LS and SANS studies has presented a clearer scenario on the thermoresponsive aggregation behavior of the investigated PS–PNIPAM–PS triblock copolymer.