乙酸乙酯在D3F阴离子开环聚合中的促进作用

Promoting Effect of Ethyl Acetate on Anionic Ring-opening Polymerization of l,3,5-Trimethyl-l,3,5-tris(3,3,3-trifluoropropyl) cyclotrisiloxane(D_3F)

以硅醇钠为引发剂,乙酸乙酯(EA)为极性调节剂,在HAAKE转矩流变仪中合成了聚三氟丙基甲基硅氧烷(PMTFPS),探讨了三氟丙基甲基环三硅氧烷(D3F)聚合过程中EA的促进作用.结果表明,在120℃下,引发剂质量分数为2.74%,EA极性调节剂浓度为0.30 mol/L,反应4 min时,PMTFPS的数均分子量(M-n)达到最大(2.45×105),产率为89.2%.通过激光解析电离飞行时间质谱(MALDI-TOF-MS)分析可知,此反应条件下环状硅氧烷副产物含量较低,仅为0.74%,说明此条件下链反咬副反应得到很好的抑制.差示扫描量热法(DSC)和热失重分析(TGA)结果表明,PMTFPS可以在较宽的温度范围内使用.

Poly[methyl（trifluoropropyl）siloxane]（PMTFPS） was prepared in the mixing chamber of a HAAKE torque rheometer using sodium silanolate as the initiator,and ethyl acetate（EA） as the promoter.The promoting effect of EA in the anionic bulk polymerization of D3F was investigated.The results show that the maximum of number average molecular weight（_n=2.45×105） of PMTFPS was obtained with high yield（89.2%） when the polymerization was carried out in the presence of 2.74%initiator and 0.30 mol/L EA at 120 ℃ for 4.0 min.The backbiting reactions were almost suppressed and 0.74% cyclic by-products were obtained by matrix-assisted laser desorption ionization time-of-flight mass spectrometry（MALDI-TOF-MS） for EA promoter system.Investigations of differential scanning calorimetry（DSC） and thermogravimetic analysis（TGA） show that PMTFPS can be used in a wide range of operational temperatures.