Spontak R J, Smith S D, Ashraf A
Corporate Research Division, Miami Valley Laboratories, Procter & Gamble Company, Cincinnati, Ohio 45239-8707.
Microsc Res Tech. 1994 Apr 1;27(5):412-9. doi: 10.1002/jemt.1070270507.
Block copolymers undergo self-organization when the blocks are sufficiently incompatible, and generate a variety of periodic morphologies in the limit of strong segregation. An equilibrium morphology only recently added to the diblock copolymer phase diagram is the ordered bicontinuous double-diamond (OBDD) morphology, which possess a Pn3m space group. It has been observed over a very narrow composition range (ca. 4 vol%), thereby making it difficult to obtain in pure copolymers. This obstacle can, however, be surmounted by blending a copolymer with one of the parent homopolymers. In the present study, several symmetric poly(styrene-b-isoprene) diblock copolymers varying in molecular weight (M) have been blended with homopolystyrene to produce the OBDD morphology. Transmission electron microscopy is employed here to identify the morphologies in cryosections of each blend and reveals that, at intermediate molecular weights, the OBDD morphology is indeed observed. At low M, near the order-disorder transition, however, a lamellar catenoid or disordered morphology is preferred. At the other extreme, high-M blends are frustrated by molecular entanglements and adopt a cylindrical morphology.
当嵌段之间的不相容性足够大时，嵌段共聚物会发生自组装，并在强相分离的极限情况下产生各种周期性形态。最近在二嵌段共聚物相图中新增的一种平衡形态是有序双连续双菱形（OBDD）形态，它具有Pn3m空间群。这种形态仅在非常窄的组成范围内（约4体积%）被观察到，因此在纯共聚物中很难获得。然而，通过将共聚物与其中一种母体均聚物共混，可以克服这一障碍。在本研究中，将几种分子量（M）不同的对称聚（苯乙烯-嵌段-异戊二烯）二嵌段共聚物与均聚苯乙烯共混，以产生OBDD形态。这里采用透射电子显微镜来识别每种共混物冷冻切片中的形态，结果表明，在中等分子量下，确实观察到了OBDD形态。然而，在低分子量时，接近有序-无序转变时，更倾向于层状链状或无序形态。在另一个极端情况下，高分子量共混物会受到分子缠结的阻碍，而呈现出圆柱形形态。
