Preparation And Properties Of Silicone Resin Containing Perfluorocyclobutyl Aryl Ether Group

Silicone resins are widely used as aerospace materials,electronic packaging materials and waterproof coatings because of their outstanding high and low temperature resistance,weatherability,electrical insulation and dielectric properties.Polymers containing perfluorocyclobutyl(PFCB)aryl ether group exhibit excellent low dielectric properties and thermal stability.The introduction of PFCB group into silicone resin is expected to obtain modified fluorosilicone resins with high thermal stabilty and low dielectric constant.In this paper,a new method of preparing fluorosilicone resins by introducing PFCB structure was explored.Firstly,two alkoxysilanes with PFCB group(PFCB-QRS)were synthesized.PFCB fluorosilicone resins was prepared by two kinds of silanes.The performance test of fluorosilicone resin shows that the fluorosilicone resins exhibit good thermal stability and low dielectric property.Details are as follows:(1)Silicone resins with different PFCB content were prepared by hydrolysis and polycondensation with PFCB-QRS and multi-functional alkoxysilanes.The viscosity-average molecular weight and crosslinking density of the resins were measured,and the refractive index,thermal stability,transmittance and dielectric constant of the resins were tested.The results showed that the PFCB silicone resins displayed increased refractive index,higher thermal stability,better light transmittance and lower dielectric constant It can be used as heat-resistant optical materials or low dielectric materials.(2)The thermal resistance of fluorosilicone resin is lower than that of the silicone resin due to the introduction of trifluoropropyl.Hexafluorocyclobutyl(PFCB)formed by trifluorovinyl releases bond tension in unsaturated double bonds,leading the more stable structure.Here,PFCB is used to modify fluorosilicone resin to improve its heat resistance.Modified fluorosilicone resins with different PFCB contents were prepared by co-hydrolysis and polycondensation of oligomethyltrifluoropropylsiloxane(OMFS),PFCB-QRS and alkoxysilanes.The structure and properties of the synthesized silicone resins were tested.The results indicate that the PFCB modified fluorosilicone resin has good thermal stability and transmittance,and its dielectric constant decreases with the increase of PFCB content.(3)The organic silicone resin prepared by hydrolysis and polycondensation method contains a large number of hydroxyl groups,which makes the silicone resin have a great tendency of self-condensation,poor storage stability and easily premature crosslinking.A new method for the preparation of hydroxyl-free PFCB silicone resin by Piers-Rubinsztajn reaction was explored using a SiH-containing PFCB compound and SiOR-containing monomers as raw materials.The preparation conditions of PFCB silicone resin by Piers-Rubinsztajn reaction between PFCB compound and TEOS were explored.FT-IR showed that there was no hydroxyl group exist in the structure of fluorosilicone resin,and its storage stability was much better than that of the silicone resin prepared by hydrolysis and polycondensation.