A Solid-State NMR Investigation of MQ Silicone Copolymers

Abstract

The structure of MQ copolymers of the general chemical formula [(CH3)3SiO0.5]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. 29Si NMR spectra were obtained by single pulse excitation (or direct polarization, DP) and cross-polarization (CP) 29Si{1H} techniques in concert with MAS. It was shown that material consist of monofunctional M (≡SiO Si (CH3)3) and two types of tetrafunctional Q units: Q4 ((≡SiO)4Si) and Q3 ((≡SiO)3SiOH). Spin–lattice relaxation times T1 measurements of 29Si nuclei and analysis of 29Si{1H} 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.

Improved processibility of silicone composites by MQ silicone resins

“…Dispersion state of silica particles is closely related to their reinforcement. As reported, better dispersion of SiO 2 powders to silicone composites increased both modulus and elasticity . The mechanical properties of silicone composites with and without MQ resins are presented in Figure .…”

“…Figure presents the 29 Si NMR spectra of MQ1.0, MQ1.1, and MQ1.2. All spectra give two resonances at 10 and −110 ppm, corresponding to Si atoms for mono‐ and quarter‐ units, respectively . Integral area of resonances are 1.02 × 10 6 (10 ppm) and 1.01 × 10 7 (–110 ppm) for MQ1.0, 1.…”

Synthesis and Properties of MQ Copolymers: Current State of Knowledge

“…In order to obtain MQ copolymers, reducing differences in reactivity of monomers M and Q is essential, which leads to obtaining a product with a ratio of M and Q units corresponding completely to the initial amounts introduced and maintained this ratio in all fractions of the copolymer [59]. …”

Alternating Copolymer of Double Four Ring Silicate and Dimethyl Silicone Monomer–PSS‐1

“…Related MQ copolymers, which are networks of Q 4 Si speciest ypically end-capped by trimethylsiloxy groups (M 1 species), have shown as imilar increaseo ft he thermals tability of the organic groups by increasing the Q 4 content of the copolymer. [58][59][60] Materialw ith high Q 4 content shows elimination of methyl groups below 700 8Ci ns imilar conditions where PSS-1 withstands at least 750 8C. [58] Other D4R containing polymers with organic groups seldom demonstrate at hermals tabilityo f these groups above 700 8C.…”