Current commodity plastics, including PET, LDPE, HDPE, PS, PP, and PVC, are predominantly carbon-based. This seems quite sensible since carbon chemistry has been studied for centuries. However, carbon constitutes only 0.02% of the earth’s crust, and an even smaller percentage of the ocean. Regarding availability to humans, oxygen and silicon are the most abundantly available elements. Therefore, in the push to develop novel sustainable commodity plastics, it is important to also look to silica as an inexhaustible starting material. The most commonly produced silicon-containing polymer is polydimethylsiloxane, which is made from silica. In order to synthesize silicon-containing polymers, silica is subjected to carbothermal reduction at 1900 °C to reduce silicon (IV) to elemental silicon, which is then oxidized back to silicon (IV) while producing useful monomers. The carbothermal reduction process can be avoided by extracting the silicon from silica using alcohols. Thermodynamic data indicates silicon prefers diols over mono-alcohols, forming silaspirocycles. These silaspirocycles can then be polymerized through alkylorthosilicate metathesis polymerization to produce polyalkylorthosilicate networks. Herein we report the optimized depolymerization of silica using chelating diols and the polymerization of the resulting silaspirocycles. We screened trifluoracetic acid, acetic acid, phosphoric acid, malic acid, and <i>p</i>-toluenesulfonic acid at catalyst loadings ranging from one crystal or one drop to 10 mol % under nitrogen and vacuum conditions with temperatures of 100-200 °C. The networks formed were analyzed using thermogravimetric analysis, differential scanning calorimetry, and infrared spectroscopy.

From silica to polymers in two simple steps

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.