Symmetry breaking of concentration fluctuations was found in a binary polymer mixture with one component photo-cross-linked by linearly polarized light. As the reaction proceeds, the mixture undergoes phase separation, exhibiting lamellar morphologies with the direction closely perpendicular to the polarization $\mathrm{}\left(E\right)\mathrm{}$ of the exciting light. It was also found that the phase separation is suppressed in the parallel direction and its kinetics strongly depends on the relative orientation with respect to the exciting polarization. Thus, these reacting mixtures provide a model system to study the directional phase separation driven by chemical reactions.

• Received 30 October 1997

DOI:https://doi.org/10.1103/PhysRevE.57.R1243