Autophobic dewetting of homopolymer on a brush and entropic attraction between opposing brushes in a homopolymer matrix

The wetting behavior of homopolymer on a chemically identical polymer brush is mathematically equivalent to the interaction between a pair of opposing brushes in a matrix of parent homopolymer. We examine both systems using s elf-consistent field theory (SCFT) with a new highly efficient and accurate algorithm. Our calculations provide compelling evidence that the global mi nimum in the free energy curve remains at a finite film thickness, implying that the brush/homopolymer interfacial tension, gamma (b/h), is always pos itive favoring dewetting, or equivalently that an attraction always exists between opposing brushes. Nevertheless, we identify a region at low homopol ymer molecular weights where gamma (b/h) is negligible, in which case compl ete wetting is highly metastable and the attraction between opposing brushe s is extraordinarily weak. Furthermore, we demonstrate that SCFT is in good quantitative agreement with experiment. In contrast, we find that earlier predictions based on strong-stretching theory are terribly inaccurate. (C) 2001 American Institute of Physics.