Compatibility of semicrystalline/amorphous ionomeric blends

Two semicrystalline/amorphous ionomeric blend systems, the blend of poly(ethyl acrylate-co-4-vinylpyridine) with metal neutralized sulfonated poly(ethylene terephthalate) (EAVP/PET-SO$\sb3$M) and the blend of nylon 4 with lithium neutralized sulfonated polystyrene (N4/SPS-Li), were investigated. The motivation of this work was to use specific interactions between the polymer pair to form miscible or compatible blends for property enhancement. Additionally, particular effort was made to address the competing phenomena between the phase mixing by virtue of the specific interactions and the phase separation possibly induced by the crystallization of the semicrystalline component. For the EAVP/PET-SO$\sb3$M blend, an extensive study was undertaken to investigate the various factors affecting the compatibility behavior and hence the ultimate mechanical properties of the system which include: (1) the effects of stoichiometry of the interacting groups upon the amorphous phase; (2) the effects of stoichiometry of the interacting groups upon the crystalline phase; (3) the effects of functionalization level of the constituent polymers; and (4) the effects of counterions of the ionomer component. Results showed that compatibilization of EAVP/PET-SO$\sb3$M was achieved by virtue of the formation of a metal-pyridine-sulfonate group coordination complex between the polymer pair. However, complete miscibilization was not obtained even at the highest level of functionalization, 10 mol %. The crystallization of the PET-SO$\sb3$M component was found to induce some phase separation, but the system remained compatibilized via specific interactions. On the other hand, the crystallization behavior was affected by the phase mixing, the level of sulfonation and the counterions of the ionomer. Dramatic improvement of the ultimate mechanical properties was accomplished as a result of the favorable interfacial adhesion across the phase boundaries as compared to the immiscible counterparts. For the N4/SPS-Li blend, the composition dependence of the compatibilization was investigated in relation to the effects of crystallinity level of the N4 component and the water content of the system. Results showed that compatibilization was achieved by virtue of the specific interactions between the amide groups and the lithium sulfonate groups. Samples with a high level of crystallinity exhibit consistently higher glass transition temperature (T$\rm \sb{g}$) than those with low crystallinity. Wet samples were found to have a lower T$\rm \sb{g}$ than the dry counterparts due to the plasticization effect