PEO temporary network in PEO/PMMA blends: NMR approach

Transverse magnetic relaxation properties of protons attached to PEO chains were investigated in compatible blends of hydrogenated PEO and deuterated PMMA by varying the PEO concentration and the temperature. The onset of segmental fluctuations is observed for samples that do not crystallize (phi less than or equal to 0.31); it occurs above T-g(PEO) but below the blend glass transition temperature, T-g(phi). At higher temperatures, for all concentrations, relaxation curves exhibit a solid-like behavior typical of a residual dipolar interaction due to the presence of a temporary network. The associated relaxation time obeys a linear temperature dependence with a reference at T-g(phi) + T-0 and a linear variation with the mean segmental spacing between two consecutive entanglements along PEO chains, as calculated from the model proposed by Tsenoglou. This study extends the relationship between NMR properties and the network mesh size already observed in permanent gels and entangled homopolymers to miscible heteropolymers.