Hexagonal phase induced by a reversible photo-cross-link reaction in a polymer mixture.

A hexagonal phase was found during the synthesis of interpenetrating polymer networks composed of polystyrene (PS) and poly(methyl methacrylate) (PMMA). By using confocal microscopy, it was found that the regularity of this hexagonal phase further increases upon de-cross-linking of the PS networks in the matrix phase by irradiation with shorter uv wavelengths. We conclude that the cooperation between the cross-link-induced suppression of phase separation and the elastic repulsion between the dispersed PMMA-rich domains is responsible for the emergence of this hexagonal phase.