Preparation of Long-Chain-Alkyl Siloxanes Bridged by Carbon-Sulfur Bond via Thiol–Ene Reaction

Long-chain-alkyl siloxanes were commonly used as hydrophobic treatment agents in cotton fabrics. In this work, long-chain-alkyl siloxanes (S-Siloxanes) were prepared by thiol–ene reaction between polyvinylmethylsiloxanes (Si  CC) and 1-pentanethiol. Thermal behavior, glass transition temperature (Tg), crystallization property, and hydrophobic treatment performance were investigated and compared with those of commonly used long-chain-alkyl siloxanes (C-Siloxanes) prepared via hydrosilylation reaction with platinum as a catalyst. The results showed that S-Siloxanes were thermally stable up to 350°C and possessed similar Tg and crystallization performance as C-Siloxanes. Water contact angles of glasses and cotton fabrics treated by S-Siloxanes reached 87.67° and 96.33° respectively, which were significantly increased compared to untreated glasses and cotton fabrics of 36.27° and 0°. The results were similar for glasses and cotton fabrics treated by C-Siloxanes. This work provides a milder and greener method to synthesize long-chain-alkyl siloxanes.