Surface and interfacial aggregation states in thin films of a polystyrene/polyrotaxane blend

Abstract

Polyrotaxane (PR) exhibits unique mechanical properties due to the ability of its cyclic molecules to move or slide along the axial chain. Thus, to design advanced polymer-based composite materials and organic devices, it is crucial to better understand the aggregation states at the surface and substrate interface in polymer films containing PR. Here, we report the depth profile of PR along the direction normal to the interface when it is mixed with polystyrene (PS). Neutron reflectivity and X-ray photoelectron spectroscopy revealed that PS and PR segregated at the surface and substrate interface, respectively, and that the extent of segregation depended on the length of PS. The surface enrichment of PS is driven by both energy and entropy, whereas the enrichment of PR at the substrate interface is energy driven. To design and fabricate advanced polymer-based multilayer devices and composite materials, it is crucial to gain a better understanding of the aggregation states at the surface and at interfaces with solid materials in polymer films. Here, we report the depth profile of polyrotaxane (PR) when mixed with polystyrene (PS), analyzed using X-ray photoelectron spectroscopy and neutron reflectivity. Our findings indicate that PS and PR segregated at the surface and the substrate interface, respectively, with the extent of segregation depending on the length of the PS chains.