AMERIPOL SN - A CIS-1,4-POLYISOPRENE
AMERIPOL SN - A CIS-1,4-POLYISOPRENE
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DOI：
10.1021/ie50556a033
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发表时间：
1956-01-01
影响因子：
--
通讯作者：
WILLSON, EA
中科院分区：
文献类型：
--
作者：
HORNE, SE;KIEHL, JP;WILLSON, EA
卡茨（Katz）在1925年使用X射线衍射技术进行的重要观察表明，仅仅拉伸天然橡胶或软硫化橡胶，就会导致至少一部分聚合物发生结晶。霍克（4）的这一实验和随后的实验强调了一点，即成功合成类似于橡胶树橡胶的聚合物的尝试必须考虑到规则性。异戊二烯聚合物中的情况很复杂，因为单体可以以多种方式进入增长的聚合物链。聚异戊二烯的四种异构形式如图1所示。由于异戊二烯分子的不对称性，必须考虑头到尾的取向，因此聚合异戊二烯中可能出现的单元有八种可能的排列。钠聚异戊二烯、钾聚异戊二烯、乳液聚异戊二烯和烯烃聚异戊二烯已被证明含有所有四种形式的重复单元（8）。所有这些未固化的聚合物具有差的粘性，并且它们的纯橡胶硫化胶显示差的物理性能。它们在拉伸或冷却时不结晶。人们早就认识到，共轭烃二烯的聚合物在其性质接近橡胶树橡胶之前必须在结构上非常规则。回顾过去的15至20年，催化剂体系的发展缓慢，起初几乎察觉不到，该催化剂体系生产的聚合物在某种程度上显示出取向结构。如果在聚合的增长阶段，单体相对于增长的链保持在一个确定的位置上，就可能产生这种取向，如通过在单体的熔点引发聚合的机械力，或通过单体吸附到固体表面上--可能是催化剂本身的表面上。本文所报道的工作主要是关于定向聚合法制造的橡胶的性质.
THE important observation, made by Katz (ß) in 1925 using x-ray diffraction technique, showed that the mere stretching of crude or soft vulcanized Hevea rubber caused at least a portion of the polymer to undergo crystallization. This and the subsequent experiments ofHock (4) emphasized the point that successful attempts to synthesize a polymer resembling Hevea rubber would have to take regularity into account. The situation is complicated in isoprene polymers by the variety of ways the monomer can enter the growingpolymer chain. The four isomeric forms of polyisoprene are shown in Figure 1. Since head-to-tail orientations must be considered because of the asymmetry of the isoprene molecule, there are eight possible arrangements of the units that can occur in polymerized isoprene. Sodium, potassium, emulsion, and alfin polyisoprenes have been shown to containall four forms of the repeating units (8). All of these uncured polymers have poor tack and their pure gum vulcanizates show poor physical properties. They do not crystallize when stretched or cooled. It has long been recognized that polymers of conjugated hydrocarbon dienes would have to be very regular in structure before their properties would approach those of Hevea rubber. Looking back over the last 15 to 20 years, there has been a slow development, almost imperceptible at first, of catalyst systems which produce polymers that in some degree show an oriented structure. This orientation could result if the monomer, during the propagation phase ofthe polymerization, is held in a definite position with respectto the growing chain, as by cybotactic forces where polymerization is initiated at themelting point of the monomer or as by adsorption of the monomer onto a solid surface—perhaps to the surface of the catalyst itself. The work reported heredeals primarily with the properties of a rubber made by directed polymerization.