C_(60)-polysulfone nanocomposite membranes: Entropic and enthalpic determinants of C_(60) aggregation and its effects on membrane properties

摘要

The study focuses on the effects of C_(60) filler on the phase inversion process and related changes in the morphology and separation properties of cast C_(60)-polysulfone nanocomposite membranes. The effects of C_(60) on the rejection and permeability of the cast membranes are correlated to rheological and demixing properties of the corresponding casting mixtures. The observed differences between C_(60)-free and nanocomposite membranes are interpreted as resulting from enthalpic and entropic C_(60)-polysulfone interactions that drive and are mediated by the aggregation of C_(60) Only 30 nm and smaller C_(60) aggregates are observed in membranes with the smallest (1 C_(60)/polysulfone by mass) C_(60) loading. In contrast, only aggregates larger than 30 nm are found in composites with 5 and 10 C_(60) loadings. A correlation between the demixing rate and permeability and a counter-correlation between permeability and rejection are observed for nanocomposite membranes for the entire C_(60) loadings range studied. The observed accumulation of the filler at the surface of internal membrane pores is attributed to the expulsion of C_(60) aggregates to the free surface for an entropic gain. The findings have implications for the design of polymer nanocomposite membranes as well as for the lifecycle analysis of nanomaterial-enabled products.