Unravelling the thermo-responsive evolution from single-chain to multiple-chain nanoparticles by thermal field-flow fractionation

Abstract

The amphiphilic block copolymer polystyrene–polyethylene oxide (PS–PEO) is shown for the first time to exhibit unique thermo-responsive transformation into single-chain nanoparticles (SCNPs), as characterized by thermal field-flow fractionation (ThFFF) with multiple detectors. In toluene, the PEO blocks are shown to fold and collapse into spheres that are stabilized by PS shells (SCNP-shells), and solvophobic interactions are prescribed as the critical determinant of the overall dynamics of formation as a function of temperature. Contrary to the typically expected random coil conformation, PS–PEO is shown to formulate SCNP–shell nanostructures. Below a critical temperature threshold of 20 °C, the SCNP–shell nanostructures are shown to collate into much larger, multiple-chain nanoparticles (MCNPs) with multiple morphologies. The associated conformational evolutions in microstructure from SCNP–shell nanostructures to MCNPs are characterized in-depth with respect to their size, shape, morphology, molar mass, and their respective distributions.