Synthesis of polysiloxanes containing trifluoroethylene aryl ether groups: The effect of promoters

Abstract

Polysiloxanes with high molecular weight (M n > 100 000, M w /M n < 2.2) containing various quantity of trifluoroethylene aryl ether groups were prepared by anion ring opening polymerization (AROP) in the presence of promoters including N,Ndimethylformamide (DMF) and N-methyl pyrrolidone (NMP). The structures of monomers and polymers were characterized by FTIR and NMR. It was found that the addition of promoter could significantly increase the polymerization rate, decrease the polymerization temperature, and increase the molecular weight of the polymer.When DMF as the promoter, the optimal conditions for polymerization were as follows: The polymerization temperature is 100 C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 160:1. The optimal conditions for polymerization using NMP as the promoter were as follows: The polymerization temperature is 75 C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 70:1, which indicated that NMP is more effective on AROP than DMF. Thermogravimetric analysis (TGA) showed that the polymer has good heat temperature resistance. Differential scanning calorimetry (DSC) showed that the introduction of NMP in bulk polymerization could improve the randomness of polymer structure, which leads to the disappearance of crystal peak and improve the low temperature resistance of polymer. K E Y W O R D S alkali catalytic system, anion ring opening polymerization, polysiloxane, promoter, trifluorovinyl aryl ether group 1 | INTRODUCTION Perfluorocyclobutyl (PFCB) polymer is a novel class of semifluorinated polymers first reported by Babb et al 1 in 1993. PFCB polymers are mainly prepared by the [2π + 2π] thermocyclization of trifluoroethylene aryl ether (TFVE) monomer. 2 Recently, PFCB polymers have attracted extensive attention of researchers in various fields including electronics industry, 3-7 aerospace, 8 fuel cells, 9-13 optical waveguide materials, 14-16 and coatings 17 because of the unique properties such as low dielectric property, low hygroscopicity, high thermal stability, chemical solvent resistance, and low birefringence. However, most of the research interests are focused on the functionality of PFCB group. There are few researches about the thermocyclization of TFVE monomer.Silicone rubber is one of the largest and most widely used organosilicon products. The traditional vulcanization methods of silicone rubber mainly include the following three categories: peroxide vulcanization, hydrosiloxane vulcanization, and functional group condensation vulcanization. Peroxide vulcanization is described that vinyl polysiloxane is cured by radical reaction using peroxides as the initiators to form a cross-linked network. However, the residues of peroxide decomposition have negative effects on the properties of silicone

Preparation of fluorosilicone rubber containing perfluorocyclobutyl aryl ether

“…In our previous work, polysiloxanes with different content of trifluorovinyl aryl ether (Si‐TFVE) in the side chain were successfully synthesized. The cyclization temperature was above 160°C 25 . In the new curing system, Si‐TFVE is used as the base gum and the vulcanization reaction is the cyclization of TFVE.…”

“…The cyclization temperature of TFVE group is in the range of 160°C‐255°C 25 . In view of the thermal stability of rubber during the curing process and the safety and economy in practical application, the curing temperature should below 200°C.…”

“…In our previous work, 25 polysiloxanes containing trifluorovinyl aryl ether (Si‐TFVE) with high molecular weight were successfully synthesized. And the polymerization process and the structure and properties of Si‐TFVE were introduced in detail.…”

Preparation of High Temperature Vulcanized Fluorosilicone Rubber by Hydrosilylation Addition Reaction

“…In our previous work [13][14][15] , we reported two kinds of uorosilicone rubber containing per uorocyclobutyl aryl ether (PFCBAE) group. Fluorosilicone rubber containing PFCBAE was rst vulcanized by the thermal cyclization reaction of tri uoroethylene aryl ether (TFVE) which was also a new vulcanization method.…”