Glaser Jens, Medapuram Pavani, Beardsley Thomas M, Matsen Mark W, Morse David C
Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455, USA.
School of Mathematical and Physical Sciences, University of Reading, Whiteknights, Reading RG6 6AX, United Kingdom.
Phys Rev Lett. 2014 Aug 8;113(6):068302. doi: 10.1103/PhysRevLett.113.068302.
Simulations of five different coarse-grained models of symmetric diblock copolymers are compared to demonstrate a universal (i.e., model-independent) dependence of the free energy and order-disorder transition (ODT) on the invariant degree of polymerization N̄. The actual values of χN at the ODT approach predictions of the Fredrickson-Helfand (FH) theory for N̄ ≳ 10(4) but significantly exceed FH predictions at lower values characteristic of most experiments. The FH theory fails for modest N̄ because the competing phases become strongly segregated near the ODT, violating an underlying assumption of weak segregation.
比较了对称二嵌段共聚物的五种不同粗粒化模型的模拟结果，以证明自由能和有序-无序转变（ODT）对不变聚合度N̄的普遍（即与模型无关）依赖性。在ODT时χN的实际值对于N̄≳10(4)接近弗雷德里克森-赫尔方德（FH）理论的预测，但在大多数实验的较低特征值时显著超过FH预测。对于适度的N̄，FH理论不适用，因为竞争相在ODT附近变得强烈分离，违反了弱分离的基本假设。
