Abstract

      The word, silicone, is familiar to most people and most are aware of at least a few silicone products. Silicone-free cosmetics are dwarfed by those that contain silicones. These ubiquitous polymers that fill so many roles are, for historical reasons, ignored in our chemistry and materials science curricula.^1-3 Most of these materials are composed of primarily dimethylsiloxane (D) groups. The General Electric Company (GE) developed a convenient shorthand⁴ to describe the structure of silicones (Figure 1).  Our ongoing research

Figure 1. The G.E. abbreviations for silicones.

on the preparation of MT (trialkylsilylmethylsilconate) and MQ (trialkylsilylsilicate) copolymers (containing no D) will be the focus of the presentation. The R groups in the monomers and the M:T and M:Q ratios are varied.

Ongoing research programs will be discussed and the preparation of MQ³ and MT copolymers by hydrolysis and condensation reactions will be a focus of the presentation. In particular, vinyl- and hydrido- functionalized samples and their curing to form transparent monolithic structures with controllable properties will be described. These materials are most often referred to as “resins” in the literature and their structures are not obvious and often aren’t even considered, although they are, in fact, molecules. Figure 2 shows the structure of an MT molecule using a drawing scheme in which the green spheres indicate tricoordinate T units and the red spheres M units. Also shown is an MQ molecule using a line drawing scheme in which the intersections indicate tetracoordinate Q units that contain attached M units (not shown) in remaining valence sites. The MT polymers are particularly versatile and the synthesis of materials based on a wide range of T precursors will be described.

Figure 2. MT and MQ molecules.