Click chemistry of PMHS for fabrication of robust, transparent and hydrophobic silicone resin coating on wood substrate at room temperature

Based on click chemistry of poly(methylhydrogen)siloxane (PMHS), an environment-friendly method was proposed for in-situ fabrication of robust, transparent, UV-resistant and hydrophobic silicone resin coating (SRC) at room temperature by simply brushing a mixture of PMHS, tetramethyltetravinyl cyclotetrasiloxane (V4), and Karstedt catalyst on wood surface. The mechanism for click chemistry of PMHS and the continuous curing characteristic of SRC was discussed based on the characterization of SRC by FTIR and XPS. The effects of the mass ratio of PMHS to V4 and curing time on the properties of SRC and the modified wood were investigated. Results showed that SRC with the mass ratio of PMHS to V4 of 5:1 possessed the best mechanical stability, and the mechanical stability increased with curing time and temperature. SRC improved significantly the hydrophobicity and water-repellency of wood by increasing the water contact angle from 27.2 degrees to 123.1 degrees and decreasing the water absorption rate from 103 % to 16 %. SRCs showed excellent transparency with an average transmittance of 92.3 % at 400-1100 nm. The UV resistance of SRC was 6 times higher than that of varnish coating. The click chemistry of PMHS will find great application in rapid fabrication of functional coatings on wood surface by using PMHS and any vinylated reagent or micro-/nano-particles.