Chemistry Seminar - Combining sulfur with silicone: a route to recyclable silicone vitrimers

Title: Combining sulfur with silicone: a route to recyclable silicone vitrimers

Speaker: A/Prof Erin Leitao, The School of Chemistry, The University of Auckland, New Zealand

Abstract: Sulfur, a waste by-product of petroleum and gas refining, accumulates at a rate of tens of millions of tons annually. In 2013, Pyun and coworkers discovered that sulfur could be used as a feedstock to make polymeric materials. Polysulfide, formed via thermal ring opening polymerisation of elemental sulfur, is stabilised when copolymerised with a variety of diene crosslinkers and has shown promise in a number of applications. In our group, we are exploiting this same chemistry to combine sulfur with silicone. Inspired by the fact that the properties exhibited by polysulfides and silicones are similar (e.g. hydrophobicity, flexibility, thermal and chemical resistance), we have incorporated both small molecule silicones into polysulfides and sulfides into silicone via crosslinking. When sulfur is combined with commercial grade silicone, the hydrosilylation crosslinking reaction is intentionally halted as sulfur poisons the Pt catalyst and sulfide crosslinks are installed in their place. This results in the production of a silicone vitrimer. The presence of the dynamic sulfur-sulfur bonds provide the ability for the silicone to be healed after being damaged. Our current work is focused on transferring this chemistry to other silicone formulations, and tuning the functionality towards developing a completely reconfigurable material that is commercially applicable.

Bio: Erin Leitao joined the University of Auckland in late 2015 after a Marie Skłodowska-Curie Postdoctoral Research Fellowship at the University of Bristol (UK). Her research group is interested in efficiently synthesizing safe-by-design functional inorganic molecules and polymers, ideally using catalysis. Where possible, renewable feedstocks are used, green chemistry principles are applied, and the degradation and fate of the materials are considered. Erin’s research projects include understanding catalytic mechanisms to improve the selectivity of forming of main-group/main-group bonds, polymer recycling (plastics, silicone), and the synthesis of replacements for PFAS, flame-retardants, pesticides as well as new materials to be used as sorbents.