过程控制对反应挤出苯乙烯/丁二烯共聚物微观结构的影响

在有机锂引发体系下,以双螺杆挤出机为反应器,苯乙烯(St)、丁二烯(Bd)混和物作为单体,四氢呋喃(THF)为极性调节剂,本体法一步合成了苯乙烯/丁二烯(S/B)共聚物.采用过氧化氢在四氧化锇作用下对聚合物分子链中Bd双键进行了深度氧化降解,通过精制除去降解的低分子产物.利用18角度小角激光光散射仪联用GPC对降解前后的样品进行分析.结果表明与通常规律相左,THF的加入使共聚物的分子量分布加宽,同时使降解后的聚苯乙烯(PS)第一嵌段分子量降低.由1H-NMR谱图计算得知,THF使1,2-聚丁二烯(PBd)比例明显增加,但THF/引发剂摩尔比值超过一定量后,1,2-PBd含量增加趋势减缓.TEM分析结果表明THF的加入导致PBd相尺寸变小而且分布趋向均匀,再次表现出过程控制分子结构的特色.

THE EFFECT OF PROCESS CONTROL ON THE MICROSTRUCTURE OF STYRENE/BUTADIENE COPOLYMERS IN REACTION EXTRUSTION

By means of a closely intermeshing twin-screw extruder as the reactor,the mixture of styrene(S) and butadiene(B) as the monomer and THF as the polar catalyst,a copolymer(S/B) was synthesized by bulk polymerization with the organic lithium initiator.The PB chain of copolymers was cleaved by reaction with hydrogen peroxide in the presence of osmium tetraoxide,then the small molecules were removed out of the system by purification.The copolymers and the segments after oxidization were characterized by GPC cooperating with a multiangle laser light scattering instrument(MALLS).It was found that the molecular weight distributions of the S/B copolymers were broadened,on the other hand,the molecular weights of the segments after oxidization decreased by addition of THF.The content of 1,2-PB was derived from~1H-NMR.It was confirmed that the content of 1,2-PB increased obviously as THF was stepped up,but to a great extent the trend of increasing was slow down.Cooperated with the survey of TEM photographs,it was confirmed that the phase of polybutadiene was minished by THF,and its distribution was more uniform.So it could be concluded that the basic mechanism of anionic polymerization during reactive extrusion was consistent with that in anionic solution polymerization,the difference only resulted from process factors during the reactive extrusion.