Anisotropic phase separation of polymer blends induced by polarization-selective reactions: Morphology and emergence mechanism

Anisotropic phase separation of polystyrene/poly (vinyl methyl ether) (PS/P VME) blends was induced by taking advantages of polarization-selective reac tions. Two types of photochemical reactions were used: photodimerization of anthracene and photoisomerization of stilbene. Anthracene and stilbene wer e separately chemically labeled to polystyrene which was mixed with PVME at various compositions to obtain samples for experiments. It was found that the anisotropic phase separation of these blends is significant when the ex perimental temperatures are below the glass transition temperature of the l abeled polystyrenes. From the time-evolution of these anisotropic morpholog ies, the phase separation kinetics was discussed in conjunction with the re action kinetics under irradiation with linearly polarized light. The eviden ce for the interference of unstable modes growing with different rates alon g different orientations in the irradiated blend, was experimentally found for both cases. These results suggest that the couplings between anisotropi c reactions and fluctuations are responsible for the emergence of the aniso tropic morphology.