A Solid-State NMR Investigation of MQ Silicone Copolymers

The structure of MQ copolymers of the general chemical formula [(CH3)(3)SiO0.5](m) [SiO2](n) was characterized by means of solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The MQ copolymers are highly branched polycyclic compounds (densely cross-linked nanosized networks). MQ copolymers were prepared by hydrolytic polycondensation in active medium. Si-29 NMR spectra were obtained by single pulse excitation (or direct polarization, DP) and cross-polarization (CP) Si-29{H-1} techniques in concert with MAS. It was shown that material consist of monofunctional M (a parts per thousand SiO Si (CH3)(3)) and two types of tetrafunctional Q units: Q(4) ((a parts per thousand SiO)(4) Si) and Q(3) ((a parts per thousand SiO)(3) SiOH). Spin-lattice relaxation times T (1) measurements of Si-29 nuclei and analysis of Si-29{H-1} variable contact time signal intensities allowed us to obtain quantitative data on the relative content of different sites in copolymers. These investigations indicate that MQ copolymers represent dense structure with core and shell.