Applying Silicon Biotechnology to the Synthesis of Structured Materials

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The 12 Principles of Green Chemistry, first proposed in 1998 by Anastas and Warner, provide chemists with guidelines for lessening the environmental impact of chemical processes. Biotechnology represents one route that can be utilized to develop green methodologies in silicon chemistry. We propose to continue our exploration of silicon biotechnology through the synthesis and study of silicon-based structured materials. Silicon biotechnology will be applied to the synthesis of two principle classes of compounds: (i) siloxane-containing phospholipids, and (ii) self-healing, recyclable silicone polymers. ******Our preliminary work has demonstrated that biocatalysis can be utilized in the synthesis of siloxane analogues of phospholipid structures. Whereas biologically relevant phospholipids typically require multiple extrusion cycles through a membrane in order to achieve unilamellar vesicles with a 100 nm diameter, siloxane phospholipids spontaneously form unilamellar liposomes with a diameter of 100-150 nm. Silicon biotechnology will be used to synthesize a library of silicon-containing lipid structures. This library of lipids will include modifications to the lipids tails and the head group, which will allow us to better understand how these siloxane-lipid molecules interact and why they spontaneously self-assemble. Modification of the lipid tails with a fluorescent tracer will make it possible to study the fluidity of these membrane systems.******Silicone polymers are ubiquitous in our world, found in applications such as lubricants, adhesives, insulators, personal care products, etc. However, one of the fundamental limitations of silicone elastomers used in such applications is that they are subject to mechanical damage, which can impinge upon the material's useful lifetime, and these materials are often difficult to recycle. In keeping with the Principles of Green Chemistry, we propose to apply silicon biotechnology to the synthesis of self-healing, recyclable silicones. Building upon our existing expertise, silicone polymers cross-linked via a Diels-Alder adduct will be explored. Linear, cyclic, and dendritic silicone will be synthesized using a chemoenzymatic approach. The capacity for these materials to heal from mechanical damage as well as their physicomechanical properties will be studied. ******Silicon biotechnology will play an integral role in the synthesis of structured materials such as silicon-containing phosphlipids and self-healing, recyclable silicone polymers. This programme will permit us to further develop our understanding of biocatalytic reactions in silicon chemistry, while concomitantly exploring interesting polymeric and biologically related silicon-containing materials.