A MODEL OF MICELLIZATION FOR BLOCK-COPOLYMERS IN SOLUTIONS
A MODEL OF MICELLIZATION FOR BLOCK-COPOLYMERS IN SOLUTIONS
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DOI：
10.1021/ma00078a035
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发表时间：
1993-12-20
期刊：
影响因子：
5.5
通讯作者：
EISENBERG, A
中科院分区：
文献类型：
--
作者：
GAO, ZS;EISENBERG, A
嵌段共聚物一般是多分散的，嵌段共聚物的分子量分布对其在溶液中的胶束化行为有着深远的影响。当嵌段共聚物浓度低于混合临界胶束浓度[CMC(Mix)]时，不溶嵌段呈球形塌陷构象。这就提出了塌缩球体的缔合能可以用Hamaker方程来描述，即相互作用能与球体半径成正比。从该模型可以得到各组分的临界胶束浓度与不溶块长度之间的关系。将此关系式与混合胶束化处理相结合，解释了CMC(Mix)与不溶链长及其多分散性的关系，并对聚(苯乙烯-b-异戊二烯)/正十六烷和聚(苯乙烯-b-丙烯酸钠)/水体系获得了满意的结果。根据这个模型，可以计算出嵌段共聚物的单链分数作为嵌段共聚物总浓度的函数。还可以得到单链和胶束部分的相对分子质量分布。CMC(Mix)随多分散指数的增加而减小。单链和胶束组分的单链分数和分子量分布受各组分的CMC对不溶性链长的依赖关系的影响。
Block copolymers are generally polydisperse, and the molecular weight distribution of a block copolymer has a profound effect on its micellization behavior in solution. When the block copolymer concentration is lower than the mixed critical micelle concentration [cmc(mix)], the insoluble block is assumed to adopt a spherical collapsed conformation. This leads to the proposal that the association energy of the collapsed spheres can be described by the Hamaker equation, i.e., that the interaction energy is proportional to the radius of the spheres. From this model, a relationship between the cmc of each component and the length of the insoluble block can be obtained. This relationship is used in combination with a treatment of mixed micellization to account for the dependence of the cmc(mix) on the insoluble chain length and on its polydispersity, and satisfactory results are obtained for the poly(styrene-b-isoprene)/n-hexadecane and poly(styrene-b-sodium acrylate)/water systems. From this model, the single chain fraction of the block copolymer can be calculated as a function of the total block copolymer concentration. The molecular weight distributions of the single chain and the micellar fractions can also be obtained. The cmc(mix) was found to decrease as the polydispersity index increases. The single chain fraction and molecular weight distributions of the single chain and the micellar fractions are found to be influenced by the dependence of the cmc of each component on the insoluble chain length.