Chapter 12: Chain Proximity of Polystyrene in Bulk Polymer, Polymer Blend and Nanocomposites

Chain proximity in polymer glasses was investigated by a new strategy combining preparation of a ²H enriched polymer blend with analysis by ¹H dipolar filtered solid-state NMR under fast magic angle spinning (MAS). Fast MAS at 25 kHz induces crucial changes in spin dynamics and selectively isolates the proton signals of hydrogenous polymer chains in which protons are sufficiently close to the ²H nuclei of deuterated polymer chains. The present NMR method is robust for characterizing the chain interpenetration in bulk polymer glasses, e.g., hydrogenated polystyrene (PS-H)/deuterated polystyrene (PS-D) blends, and chain compatibility in polymer blends, e.g., PS-D/hydrogenated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), even though the chemical shifts are completely undistinguishable for the two components, which is extremely challenging for traditional NMR techniques. In polymer/inorganic nanoparticle nanocomposites, the chain proximity could be explored by ¹H dipolar filtered solid-state NMR under fast MAS, on the basis of the dynamics difference generated by the inorganic interface. The understanding of chain proximity at a short length scale of 0.5 nm provides us better insights into achieving better performance of polymer materials.