Study Of The Activity Of Polysiloxanolate Anion And Preparation Of Fluorine-containing Polysiloxanes

Ring-opening polymerization of cyclosiloxanes initiated by polysilonalate anion is one of the important methods for synthesizing polysiloxane polymers.In this work,the factors,such as solvents,temperature,molecular structure,cations,concentration,which affect the activity of polysilonalate anion were studied by measuring electrical conductivity of alkali-metal polysilonalate.The mechanism of polymerization of cyclosiloxanes catalyzed by polysilonalate anion was explored.Polydimethylsiloxane-co-poly(trifluoropropylmethyl)siloxane copolymers(PDMS-co-PMTFPS)were synthesized by co-polymerization of(3,3,3-trifluoropropyl)methylcyclotrisiloxane(D3F)and octamethylcyclotetrasiloxane(D4)using polysilonalate anion as catalyst in the presence of promoter.The properties of PDMS-co-PMTFPS were studied in detail.Lithium poly(trifluoropropylmethyl)silanolate(PMFSiOLi),sodium poly(trifluoropropylmethyl)silanolate(PMFSiONa),potassium poly(trifluoropropyl-methyl)silanolate(PMFSiOK),potassium polydimethylsilonalate and potassium polymethylvinysilonalate were prepared.Elthy acetate(EA),tetrahydrofuran(THF),N,N-dimethylformamide(DMF),1-methyl-2-pyrrolidone(NMP)and dimethyl sulfoxide(DMSO)were used as solvents for measuring the activity of polysilonalate anion.The factors of alkali-metal cations,polysiloxane chains,chemical structure of polysilonalate,temperature and concentration of alkali-metal polysilanolate that affect the activity of polysilonalate anion were investigated by measuring electrical conductivity of alkali-metal polysilonalate solutions.The results showed that the electrical conductivities of PMFSiOLi,PMFSiONa and PMFSiOK in EA and THF were slightly different.For EA solutions,the electrical conductivities of PMFSiOLi,PMFSiONa and PMFSiOK were 0.21?S/cm,2.1?S/cm and 3.01?S/cm,respectively.For THF solutions,the electrical conductivities of PMFSiOLi,PMFSiONa and PMFSiOK were 1.68?S/cm,5.78?S/cm and 7.55?S/cm,respectively.However,for DMF solutions of PMFSiOLi,PMFSiONa and PMFSiOK,their electrical conductivities were 29.88?/cm,172.08?S/cm and 192.98?S/cm,respectively.Obviously,strong polar solvents showed a large effect on the activity of polysilonalate anion.The electrical conductivities of PMFSiOLi in THF with number average degree of polymerization of 55,69 and 83 were 7.55?S/cm,7.38?S/cm and 7.46?S/cm,respectively.The polysiloxane chains had a little effect on the activity of polysilonalate anion in the system.The electrical conductivities of potassium polymethyvinysilonalate and PMFSiOK were larger than that of potassium polydimethylsilanolate in the same solvents.In the temperature range of 20? to 40?,the electrical conductivity of PMFSiOLi solutions increased with temperature increasing.The electrical conductivity of PMFSiOLi in DMF was 22.34?S/cm at 20?.However,it was 36.98 ?S/cm at 40?.A series of fluorine-containing polydimethylsiloxane-co-poly(trifluoropropyl-methyl)siloxane copolymers were synthesized from D3F and D4 using lithium silanolate as initiator in the presence of promoter.The structure and molecular weights of PDMS-co-PMTFPS were characterized by FTIR,1H NMR,and GPC.The glass transition,crystallization behavior and thermal properties of PDMS-co-PMTFPS were further studied.The TGA results showed that the thermal stability of PDMS-co-PMTFPS copolymers gradually reduced with contents of CH2CH2CF3(CH3)SiO unit in PDMS-co-PMTFPS copolymers increasing.The TGA curve showed only one degradation stage of PDMS-co-PMTFPS when the content of CH2CH2CF3(CH3)SiO unit was less than 50%(mol%).Two degradation stages of PDMS-co-PMTFPS with more content of CH2CH2CF3(CH3)SiO unit in the copolymer chains was found.The DSC results showed that PDMS-co-PMTFPS copolymers exhibited one glass transition temperature and no crystallization phenomenon.The glass transition temperature of prepared PDMS-co-PMTFPS copolymers was in the range of-117 ? to-75 ?.