Surface and Bulk Phase Separation in Block Copolymers and their Blends. Polysulfone/Polysiloxane.

摘要

The relationship between bulk phase separation and surface segregation was elucidated in a series of polysulfone/polysiloxane alternating block copolymers and their blends with polysulfone. X-ray photoelectron spectroscopy (XPS) with angular dependence was used to obtain the compositional information from the top 6 nm of the surfaces, and transmission electron microscopy (TEM) was used to characterize the bulk morphologies. In general, solvent-cast neat block copolymers had a layer (>6 nm) at the surface enriched in siloxane and the bulk had 10-50-nm microphase-separated domain structures. In the case of blends, siloxane surface enrichment was relatively high, even at bulk concentrations as low as 0.05% w/w siloxane. The surface siloxane concentration showed a rapid increase between 1 and 10% w/w bulk siloxane concentration, corresponding to the appearance of 0.1-10-micron diameter macrophases of block copolymer in the bulk. The blend surfaces attained surface compositions equivalent to pure copolymer at bulk concentrations above 10% siloxane, where phase inversion occurred in the bulk. (jes)