The impact of zinc neutralization on the structure and dynamics of precise polyethylene acrylic acid ionomers: A solid-state 13 C NMR study

Solid-state 13C NMR experiments were performed on a series of linear poly(ethylene-co-acrylic acid) (E-AA) copolymers with the carboxylic acid group spaced precisely or randomly along the polyethylene backbone in order to determine the impact that molar percent acid content and acid group spacing have on the structure and dynamics of these materials. The impact of Zn-neutralization is investigated in precise E-AA ionomers. 13C cross-polarization (CP) NMR experiments with 1H dipolar or 1H spin-lock filters were utilized to identify the amorphous or crystalline components in the materials. Constraints extracted from the filtering experiments were used to fit quantitative NMR data for samples that contained both crystalline and amorphous regions. All random copolymers contained crystalline phases, while only the precise sample with the longest polyethylene run between acid groups (twenty CH2 groups) contained a crystalline component. The crystalline phase in this precise copolymer decreased with increasing zinc content.