Miscibility of poly(butyl acrylate)-poly(butyl methacrylate) sequential interpenetrating polymer networks

The aim of this work is to study by means of dielectric and dynamic-mechani cal techniques the miscibility and molecular mobility of sequential interpe netrating polymer networks (IPNs). Sequential poly(butyl acrylate)/poly(but yl methaerylate) interpenetrating networks with different cross-linking den sities were prepared using ethylene glycol dimethacrylate as cross-linking agent. Loosely cross-linked IPNs undergo phase separation, as detected by t he occurrence of two clearly differentiated main dielectric and dynamic-mec hanical relaxation processes corresponding to the two components. Forced co mpatibilization phenomenon appears in the highly cross-linked IPNs. The IPN cross-linked with 10% EGDMA shows a single main dynamic-mechanical relaxat ion process. Only the a main relaxation process appears in the PBA networks within the temperature range of the experiments conducted in this work. Th e dielectric relaxation spectrum of PBMA, networks shows the well-known bet a and a relaxation processes, which coalesce in a single alpha beta relaxat ion in the merging region. In the compatibilized IPNs, both the a and the b eta relaxation shift toward lower temperatures as the amount of PBA segment s in the IPN increases. The merging region shifts toward lower temperatures as well. In addition to these relaxation processes originated by the homog eneous mixture of PBA and PBMA segments, the IPNs containing more than 50% PBA also show the main PBA's dielectric relaxation process slightly shifted toward higher temperatures. This fact implies that an important part of th e PBMA segments is mixed with PBA at the molecular level.