三检测体积排除色谱表征聚合物支化结构

Use of Triple Detection Size Exclusion Chromatography to Characterize Polymer Branching Structures

以α-溴代异丁酸叔丁酯(t-BBiB)为引发剂,CuBr/联二吡啶为催化体系,二乙烯苯(DVB)为支化单体,采用原子转移自由基聚合反应(ATRP)经过一步加料方法和先臂后核方法分别合成不同支化结构类型的支化聚合物,同时以四官能度引发剂经ATRP合成臂数确定的星形聚合物为参照。采用三检测体积排除色谱(TD-SEC)得到Zimm相对支化因子g′与g和表征聚合物支化结构类型的指数因子ε(g′=gε)。结果表明:随支化结构类型的不同,支化结构指数因子ε表现出不同的分子量依赖特性。星状支化聚合物的ε平均值<1,而且随分子量的变化保持相对恒定;无规支化聚合物的ε平均值>1,而且其值随分子量的增加不断减小。因此,可以由三检测体积排除色谱进行分析确证聚合物的支化结构类型。

The branched polymers with different branching structures were synthesized through atom transfer radical polymerization （ATRP） via controlling the adding method of divinylbenzene （DVB）. The four-arm star polymers with different arm length were also prepared by ATRP as the reference for branching structure characterization. Triple detection size exclusion chromatography （TD-SEC） analysis showed that the exponential factor ε had a strong molecular weight dependence, here, ε （g＇=g＊） is the branching structure parameter expressed by Zimm branching factors g＇= [Intrinsic Viscosity]branched/[Intrinsic Viscosity]inear and g = [Mean Square Radii of gyration]branchia/[Mean Square Radii of gyration]linear at the same molecular weight. The average ε value of star-like branched polymers was less than unity, and remained relatively constant with the change of molecular weight; while the average ε value of randomly branched polymers was larger than unity, and decreased gradually with increased molecular weight. Therefore, the polymer branching structure can be characterized using TD-SEC.