Backbiting-minimized synthesis of fluorosilicone copolymers with promoter by anionic ring-opening polymerization

Abstract

A back-biting reaction in fluorosilicone synthesis can compromise its precision–manufactured mechanical properties and deteriorate its molecular properties. This phenomenon can potentially disrupt the intricate structure of fluorosilicone, diminishing its durability and altering its properties over time. Cyclosiloxane with methyl and vinyl groups was added to overcome the limited properties of poly[methyl(trifluoropropyl)siloxane] and conventional rubber for harnessing versatile materials, such as vehicles and spacecraft. In this study, dimethyl carbonate, diethyl carbonate, and allyl methyl carbonate were used as promoters to suppress back-biting reactions, and an improved fluoro-vinyl-methyl silicone (FVMQ) was synthesized. 29Si nuclear magnetic resonance (NMR) spectroscopy showed that the cyclic by-products from the back-biting reaction were inhibited by adding carbonate materials. Moreover, the conversion of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane also increased as the amount of promoter increased. The roles of varying carbonate promoters in altering the properties of FVMQs were studied using 1H NMR spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. Furthermore, the intermediate of FVMQs was prepared and analyzed using Fourier transform infrared spectroscopy, 1H NMR spectroscopy, and gel permeation chromatography to determine the mechanism of suppressing back-biting. The results showed that controlled synthesis of FVMQs by inhibiting the production of cyclic by-products with promoters will improve silicone polymer synthesis and the vehicle industry requiring high yields of fluorosilicone copolymers.