P. Bian, D.H. Flagg, T.J. McCarthy
University of Massachusetts,
United States
Keywords: silicones, MQ resins, MT resins
Summary:
Our research group is revisiting the classic (more than half century - old) silicone preparative methodologies with objectives of (1) preparing materials for applications that were not envisioned when the synthetic strategies were developed, (2) describing what are well-known as “silicone resins” instead as “silicone copolymers” with molecular structures that have not been considered, but are likely important perspectives for property control, and (3) putting silicone chemistry and technology into an academic framework that can be readily incorporated in chemistry and materials science curricula. The wonderful 4-letter “General Electric alphabet” (M D T Q), that forms self-defining words (e.g. M3QD2TM2) which can be understood with geometric precision and even dynamic understanding, is taught in few academic locations. Far more academics can pronounce “silsesquioxane” than know what an MQ resin is. Our research that was recently focused on preparing reactive MQ copolymers has moved to MT copolymers. Commercial silicones are dominated by D-based materials, but MQ, DT and T resins are also important. The academic literature is filled with the abbreviation “PDMS, -(D)n-, that is used without prejudice to label many different things, as well as “POSS” and silsesquioxane that generally connote T8 polycyclic oligomers. Absent from the academic literature and almost absent from commercial materials are MT resins/copolymers. This absence is surprising because of the availability of a broad range of both M (RMe2Si-X) and T (RSiX3) monomers. This should permit the preparation of a broad range of materials. Ongoing research programs will be discussed and the preparation of MQ 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.