Synthesis And Characterization Of The Liner Polysiloxanes Catalyzed With Solid Acid

As the most common category of silicone product,Polysiloxanes have widely been used in many area because of their excellent.This paper concentrates on the synthsis of high molecular weight liner polysiloxanes catalyzed by solid acid,focusing on the studies of the influence of various reaction factors,characterization of polymers,the detailed work are follows:The high viscosity polydimethylsiloxanes were synthsised by ring opening polymerizationofoctmethylcyclotetrasiloxane?D₄?end-cappedwith hexamethyldisiloxane?MM?catalyzed with strong acidic cation exchange resin?NKC-9?.The effects of polymerization temperature,polymerization time,catalyst dosage and end-capped reagent on the polymerization were studied and discussed.The preferable conditions for ring-opening polymerization by single-factor experiment were as follows:polymerization at 80°C for 3.5h,n?D₄?:n?MM?=75;catalyst dosage was 7wt%of the amount of monomer.The yield of the polydimethylsiloxanes obtained was 88.51%,and the viscosity was 2.35×10⁴mPa.s.The high molecular weight vinyl terminated fluorine-containing polysiloxanes were synthsised by ring opening copolymerization of octmethylcyclotetrasiloxane with1,3,5-trimethyl-1,3,5-tris?3,3,3,-trifluoropropyl?cyclotrisiloxane?D₃F?end-cappedwith1,1,3,3-Tetramethyl-1,3-divinyldisiloxane?V?catalyzed with strong acidic cation exchange resin.The effects of catalyst dosage,polymerization time,monomer feed ratio,polymerization temperature and end-capped reagent on the copolymerization were studied and discussed.The preferable conditions for ring-opening copolymerization by single-factor experiment were as follows:polymerization at 80°C for 8h;n?D₄?/n?D₃F?=7:3,n?D₄?/n?V?=75;catalyst dosage was 7wt%of the amount of monomers.The yield of the vinyl terminated fluorine-containing polysiloxanes obtained was 80.27%,and average molecular weight was 6.41×10⁴g/mol.The hydrogen-terminated polydimethylsiloxane?H-PDMS?and the vinyl-terminated polydimethylsiloxanes?V-PDMS?were obtained by ring opening polymerization of octamethylcyclotetrasiloxane catalyzed with strong acid cation exchange resin end-cappedwith1,1,3,3-Tetramethyl-1,3-divinyldisiloxaneand1,1,3,3,-Tetramethyldisiloxanerespectively.Thehighmolecularweightlinear polycarbosiloxanes were synthesized by Pt-catalyzed hydrosilylation copolymerization of H-PDMS and V-PDMS in dilute solutions.The effects of catalyst dosage,polymerization time,the mole ratio of Si-Vi to Si-H groups,polymerization temperature on hydrosilylation copolymerization were studied and discussed.The preferable conditions for hydrosilylation copolymerization by single-factor experiment were as follows:copolymerization at 50°C for 10h;n?Si-Vi?/n?Si-H?=1.2/1;Pt catalyst dosage was 4ppm weight of the prepolymers.The weight-average molecular weight?Mw?measured by viscosity method exceeded2.0×10⁴g/mol.A series of characterization tests were performed on the polymers.The molecular structures of the polymers were measured by FT-IR and ¹H-NMR spectroscopy.The molecular weight distributions and average molecular weight of the polymers were measured by GPC.The thermal properties of the polymers were measured by TGA.The glass transition temperature of the polymers were measured by diffenertial scanning calorimetry.The weight-average molecular weight?Mw?measured by viscosity method.