Degree of Association of Polystyryl-, Polyisoprenyl-, and Polybutadienyllithium in Hydrocarbon Solvents
Degree of Association of Polystyryl-, Polyisoprenyl-, and Polybutadienyllithium in Hydrocarbon Solvents
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烃类溶剂中聚苯乙烯基、聚异戊二烯基和聚丁二烯基锂的缔合度
DOI：
10.1021/ma60028a012
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发表时间：
1972
期刊：
影响因子：
5.5
通讯作者：
S. Bywater
中科院分区：
文献类型：
--
作者：
D. Worsfold;S. Bywater
苯乙烯、丁二烯和异戊二烯（Li逆离子）的活性聚合物的结合度主要是通过环己烷中的光散射测量来评估的。用浓溶液粘度进行了一些测定。确定了苯乙烯化合物的缔合数为2，丁二烯和异戊二烯聚合物的缔合数为4。后一种聚合物在低浓度下表现出部分解离成二聚体。描述了在这些系统中解释浓溶液粘度测量时遇到的困难。本文认为，这些困难是导致文献中发现的关联数不一致的原因。烃类单体与烷基锂反应形成的聚合物的活性链端在烃类溶液中缔合。然而，在关联程度上存在分歧。一些报告表明，在所有情况下，它都是双重的，但另一些报告则指出，它因所涉及的单体而异。在过去，对于这些聚合反应中增殖反应的动力学顺序也存在类似的分歧。在所有的情况下，活性链末端的顺序都是半序，但其他研究发现，这种顺序因所涉及的单体而异。2-s， T-9通过改进技术的应用
The degrees of association of living polymers of styrene, butadiene, and isoprene (Li counterion) havebeen evaluated principally by means of light-scattering measurements in cyclohexane. Some determinations were made using con-centrated solution viscosities. It was confirmed that the association number was two for thestyrene compound and four for the butadiene and isoprene polymers. The latter polymer shows partial dissociation to dimers at low concentrations. The difficulties encountered in interpretation of concentrated solution viscosity measurements in these systems are described. It is suggested that these difficulties are responsible for the discordant values of association number found in the literature. he active chain ends of polymers formed by the action of lithium alkyls on hydrocarbon monomers are associated in hydrocarbon solution. 1-6 There has, however, been disagreement concerning the degree of association. Some reports suggest that it is twofold in all cases, 1 23456 789but others state that it varies with the monomer involved. 7-10 Similar disagreements existed in thepast about the kinetic order of the propagation reaction in these polymerizations. A half-order with respect to the active chain ends in all cases11 has been suggested, but other studies found that the order varied with the monomer involved. 2-s, T-9 By the application of improved techniques