Synthesis of Silphenylene-Containing Siloxane Resins Exhibiting Strong Hydrophobicity and High Water Vapor Barriers

Abstract

The novel phenylenedisilane, 1,4-bis(dimethoxyphenylsilyl)benzene (BDMPD), was successfully synthesized via the reaction between trimethoxyphenylsilane (TMPS) and a Grignard reagent originating from 1,4-dibromobenzene. In comparison to common Grignard reactions, this process was a facile one-pot method. 1H NMR spectroscopy, FT-IR measurements, and elemental analysis confirmed the predicted structure of BDMPD. In addition, vinyl-terminated polysiloxanes containing silphenylene units (VPSSP), which were hydrolytically copolymerized from BDMPD, TMPS, and divinyltetramethyldisiloxane, exhibited excellent thermal stabilities (T10%: 502 °C, Rw%: 76.86 beyond 700 °C) and suitable refractive indices (1.542). Furthermore, water contact angle and water vapor permeability tests confirmed that the fully cured siloxane resins containing VPSSP-based silphenylene units exhibited strong hydrophobicity (water contact angle: 119°) and superior water vapor barrier properties, thereby indicating their potential to serve as strong waterproof coatings for moisture-proof applications or as adhesives for use in immersed equipment.