STRUCTURE-PROPERTY RELATIONSHIP OF POLYMER BLENDS WITH CO-CONTINUOUS STRUCTURES PREPARED BY PHOTO-CROSS-LINKING

Polymer blends with co-continuous structures in the micrometer scale w ere obtained by photo-cross-linking of poly(2-chlorostyrene)/poly(viny l methyl ether) (P2CS/PVME) mixtures undergoing the spinodal decomposi tion process. The reaction was carried out with UV light at 365 nm to induce the photodimerization of anthracenes labeled on the P2CS chains (P2CS-A). To obtain the blends with co-continuous structures of varyi ng length scales (lambda), P2CS-A/PVME blends having the same cross-li nk density were prepared by irradiation and subsequently annealed over different time intervals. The resulting morphology was observed by us ing phase-contrast optical microscopy and was analyzed by digital imag e analysis. It was found that the time evolution of these co-continuou s structures follows the power law lambda proportional to t(a), where alpha is close to 1/4. This value is smaller than 1/3, as predicted by the Lifshitz-Slyozov-Wagner law, indicating that the spinodal decompo sition was slowed down by the presence of cross-links. The physical pr operties of these photo-cross-linked blends were examined by dynamic m echanical measurements. For the same cross-link density, the storage m odulus E' of P2CS/PVME blends increases with lambda, whereas the loss peaks of these co-continuous structures shift to the high temperature side. These experimental results suggest that the combination of photo -cross-linking reactions and the phase separation kinetics of polymer blends has the potential of providing a new way to design multiphase p olymer materials with controllable co-continuous structures in the mic rometer range.