3-巯基己醇在苯乙烯聚合体系中的链转移反应行为

Study of the Chain Transfer Reaction of 3-Mercaptohexanol in the Styrene Polymerization

以偶氮二异丁腈(AIBN)为引发剂,甲苯为内标,3-巯基己醇为链转移剂进行苯乙烯(St)聚合。根据Mayo等式,求出了60℃,70℃和80℃下的链转移常数,分别为3.99,3.58和2.24,表明链转移常数随着温度的升高而减小。采用制备色谱分离得到了聚合初期的产物,并且由核磁共振(1 H NMR)和液-质联用(LC-MS)确证了生成的小分子产物的结构。定量分析结果表明:在相同的巯基醇转化率下,相对分子质量低的产物的生成量随反应温度的升高而显著增加,以聚合物相对分子质量为基础计算得到的表观链转移常数则变小。

The polymerization of styrene was carried out in the presence of 3-mercaptohexanol at different temperature with AIBN as the initiator and toluene as the internal standard.The chain transfer constant of 3-mercaptohexanol under the experimental condition was obtained by the Mayo equation.It is 3.99,3.58 and 2.24 at the polymerization temperature of 60 ℃,70 ℃ and 80 ℃ respectively.As the temperature increased,the chain transfer constant of 3-mercaptohexanol decreased.Further research showed that： under the polymerization condition,the products with very low molecular weight were formed from the 3-mercaptohexanol transferring to styrene radical.The dimer and trimer of these products were obtained by high performance liquid chromatography and confirmed by proton nuclear magnetic resonance（1H NMR） and liquid chromatography-mass spectrometry（LC-MS）.The productivity of these products increased significantly as the reaction temperature increased.Therefore,the obtained chain transfer constant is only the apparent value because of the formation of the molecules with very low molecular weight.