HIGH-RESOLUTION SOLID-STATE C-13 NUCLEAR-MAGNETIC-RESONANCE STUDY OF A POLYMER COMPLEX - POLY(METHACRYLIC ACID) POLY(ETHYLENE OXIDE)

The inter-polymer interaction, morphology and molecular motion of the poly(ethylene oxide)/poly(methacrylic acid) (PEO/PMAA) complex were in vestigated by measuring various nuclear magnetic resonance parameters, such as C-13 chemical shift, (HT1)-H-1, (HT1p)-H-1, (HT2)-H-1 and (CT 2)-C-13. For the complex, we observed two peaks for the carboxyl carbo n of PMAA. We assigned the higher-field resonance to the carboxyl grou p that forms hydrogen bonds to PEO (the complex form), and the lower-f ield one to the group that forms hydrogen bonds among PMAA (the dimeri c form). It is shown that, for temperatures within 100 K below T-g, th e complex form easily breaks up and rearranges to the dimeric form. Fo r the complex, the (CT2)-C-13 and (HT2)-H-1 reveal that PEO is mobile, whereas PMAA is rigid. This different mobility between PEO and PMAA m ay facilitate breakage of the hydrogen bonding between PEO and PMAA. E xamination of H-1 spin diffusion in the complex reveals that the dista nce between PEO and PMAA in the complex is similar to that between PEO and PMAA in the dimeric form. These results show that the PMAA in the dimeric form does not aggregate to form a domain structure, and that the PEO/PMAA complex is miscible on a segmental scale. Furthermore, th e thermal degradation of PMAA in the complex was examined. Dehydration occurs in the dimeric form to produce anhydride, and the reaction tem perature is much lower than that of pure PMAA.