LAMELLAR DIBLOCK COPOLYMER GRAIN-BOUNDARY MORPHOLOGY .1. TWIST BOUNDARY CHARACTERIZATION
LAMELLAR DIBLOCK COPOLYMER GRAIN-BOUNDARY MORPHOLOGY .1. TWIST BOUNDARY CHARACTERIZATION
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DOI：
10.1021/ma00069a016
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发表时间：
1993-08-16
期刊：
影响因子：
5.5
通讯作者：
HOFFMAN, D
中科院分区：
文献类型：
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作者：
GIDO, SP;GUNTHER, J;HOFFMAN, D
用透射电子显微镜研究了聚丁苯-丁二烯层状嵌段共聚物的晶界形态。观察到了两种类型的扭曲晶界，在晶界区域，两个块体的微相分离通过材料间的分割面来保持，这些分割面近似于经典的最小表面。当实验图像和模拟图像中的投影方向发生系统变化时，通过比较实验图像和模型表面的光线跟踪计算机模拟，证明了这些界面的几何形状。观察到的两种形貌都有材料间的分割面，它们要么接近谢尔克的第一个(双周期)表面，要么接近右螺旋面的一部分。螺旋面边界在小于或等于15度左右的低扭转角度下观察到。在从0度到90度的整个扭转范围内，发现了由双周期鞍面阵列组成的谢克曲面族的边界形态。当扭转角度接近0度时，Scherk表面晶界形态转变为具有单一螺旋面几何形状的材料间分割面的单个螺型位错。给出了这种螺位错的详细核心结构的直接透射电子显微镜成像。这些图像表明，在层状两嵌段共聚物中，螺型位错核是非奇异的。这种非奇异的核心结构从根本上偏离了原子晶体中位错的经典研究中所观察到的奇异核心结构。
Grain boundary morphologies in poly(styrene-b-butadiene) lamellar diblock copolymers were characterized using transmission electron microscopy (TEM). Two types of twist grain boundaries were observed in which microphase separation of the two blocks was maintained in the grain boundary region by intermaterial dividing surfaces that approximate classically known minimal surfaces. The geometry of these interfaces was demonstrated by comparing experimental TEM images with ray tracing computer simulations of the model surfaces as the projection direction was systematically varied in both the experimental and simulated images. The two morphologies observed were found to have intermaterial dividing surfaces that approximate either Scherk's first (doubly periodic) surface or a section of the right helicoid. The helicoid section boundary was observed at low twist angles, less than or equal to about 15-degrees. The Scherk surface family of boundary morphologies, which consists of a doubly periodic array of saddle surfaces, was found over the entire twist range from 0 to 90-degrees. As the twist angle approaches 0-degrees the Scherk surface grain boundary morphology is transformed into a single screw dislocation that has an intermaterial dividing surface with the geometry of a single helicoid. Direct TEM imaging of the detailed core structure of this screw dislocation is presented. These images demonstrate that in the lamellar diblock copolymer the screw dislocation core is nonsingular. This nonsingular core structure represents a radical departure from the sigular core structures observed in classical studies of dislocations in atomic crystals.