Fluorinated Siloxane Polymers Formed by Cyclization of Trifluorovinyl Aryl Ethers with Tunable Properties

The [2π + 2π] thermal cyclization of trifluorovinyl aryl ethers (TFVAEs) provides an effective method for preparing special fluorinated polymers that contain perfluorocyclobutyl (PFCB) rings. TFVAE monomers containing siloxane segments with 2, 3, 4, and 8 functionalities were synthesized. A series of PFCB fluorosilicone polymers with high thermal stability are prepared by [2π + 2π] thermal cyclization-induced copolymerization of bifunctional monomers and multifunctional monomers. The thermal, mechanical, and dielectric properties of the PFCB polymers can be finely tuned in a wide range by changing the bifunctional monomer, multifunctional monomer, and the monomer ratio. The glass-transition temperature (Tg), initial modulus, ultimate strength, and ultimate elongation of the prepared PFCB copolymers are adjusted from −20 to 162 °C, 0.12 to 400 MPa, 0.1 to 30 MPa, and 8 to 230%, respectively. The Tgs of PFCB copolymers are correlated with their dielectric properties. The high Tg PFCB polymer shows a low dielectric constant and loss factor. The PFCB polymer with Tg of 162 °C exhibits a dielectric constant of 2.53 and a loss factor of 10–3 while that with Tg of −6 °C shows a dielectric constant of 2.86 and a loss factor of 10–2 at 106 Hz.