K. Saalwächter, Y. Thomann, A. Hasenhindl, H. Schneider.
Observation of Interphase Composition in Block Copolymers.
Macromolecues 41, 9187-9191 (2008). DOI 10.1021/ma802094h.
We demonstrate the fast, direct, and quantitative observation of temperature-
and comonomer-induced changes in the interfacial size and composition in
phase-separated styrene-butadiene-styrene block copolymers by
double-quantum-filtered proton spin-diffusion NMR experiments performed under
high-resolution magic-angle spinning conditions. The experiment is based on the
dipolar-mediated diffusion of spin magnetization from the (styrenic) rigid phase
through a more mobile interphase of variable size and composition into the soft
(polybutadiene) domain. The experiment spectroscopically distinguishes between
mobilized styrene segments located in the interphase and those mixed (dissolved)
in the bulk of the mobile domain. The results indicate that temperature-induced
softening due to mobilization of styrene units at the interface and the tendency
to become part of an extended interphase is stronger for systems with a lower
segregation strength, having statistically distributed styrene comonomers in the