Mobility, Structure, and Domain Size in Polyimide−Poly(dimethylsiloxane) Networks Studied by Solid-State NMR Spectroscopy

Dynamics, structure, and domain size in polyimide−poly(dimethylsiloxane) networks (PI−PSX) with various compositions were investigated by solid-state NMR spectroscopy. 29 Si and 13 C MAS NMR spectroscopy revealed the presence of PSX chains in two motional states, and their relative content was estimated. The overall mobility as well as local motions was studied by 1D and 2D 1 H wide-line spectroscopy. 2D WISE spectra proved large differences in molecular mobility of PSX and PI chains. High mobility of PSX is not imparted to rigid PI, and the interfacial region is located in the PSX phase. This region corresponds to the immobilized PSX chains at the surface of PSX domains, which link PI chains. The spherical morphology and domain sizes at the nanometer scale were determined from analysis of spin diffusion processes. Molecular mechanics and dynamics calculations were performed to design PSX domains at the atomic level. Correlation of the structure and morphology with mechanical and thermal properties is discussed.