Design, synthesis and properties of trifluoromethyl polysiloxane oxetane monomers

The oxetane is widely used in cationic photopolymerization, while fluorosilicone polymers combine the advantages of organosilicone and organofluorine. In this study, a series of trifluoromethyl polysiloxane oxetane monomers with different chain length (XE-FSin, n = 3, 6, 9) was designed and synthesized by a simple two-step synthesis procedure, and low-cost and easily available raw materials. XE-FSin exhibited good photopolymerization property and ability to boost the photopolymerization of the alicyclic epoxy monomers, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (E4221) and 1,2-epoxy-4-vinylcyclohexane (VOH). The final conversions of the alicyclic epoxy group and the oxetane group of the systems with XE-FSi3 after 900 s of the irradiation reached up to 80.8 % and 75.2 %, respectively. The introduction of XE-FSin improved the thermal stability, glass transition temperature (Tg) and tensile property of the UV-cured film because of the presence of trifluoromethyl group and polysiloxane chain. The surface of the UV-cured film of XE-FSi9-0.5 % system had the highest water contact angle that was 108.4°. The tensile strength and elongation at break of the UV-cured film of XE-FSi3-0.5 % system were 0.85 MPa and 67.87 %, respectively, and three times more than those of XE-FSi3-0 % as the blank control. With the increase of the chain length of XE-FSin, the Tg, adhesion force and pencil hardness of the UV-cured film had no significant changes.