Test of a scaling hypothesis for the structure factor of disordered diblock copolymer melts
Test of a scaling hypothesis for the structure factor of disordered diblock copolymer melts
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DOI：
10.1039/c2sm26536b
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发表时间：
2012-01-01
期刊：
影响因子：
3.4
通讯作者：
Morse, David C.
中科院分区：
文献类型：
--
作者：
Glaser, Jens;Qin, Jian;Morse, David C.
稠密聚合物液体（如嵌段共聚物熔体）的粗粒理论预测平衡性质对几个无量纲参数的普遍依赖性。对于对称的二嵌段共聚物熔体，这样的理论预测仅对chi N和（N）over bar的普遍依赖性，其中chi是有效的相互作用参数，N是聚合度，并且（N）over bar是重叠的量度。我们测试是否从几个不同的模拟模型得到的结构因子S（q）的模拟结果是一致的，这两个参数的标度假设。我们比较了三种模型的结果：（1）晶格蒙特卡罗模型，键涨落模型，（2）珠弹簧模型与苛刻的排斥相互作用，类似于Kremer和Grest的，和（3）珠弹簧模型之间的非常软的排斥，强烈重叠珠。我们比较了不同模型的模拟结果，这些模型被设计为具有匹配的（N）值，在chi N和N的值范围内，并设计方法来测试缩放假设，而不依赖于任何预测的现象学相互作用参数chi如何依赖于更微观的参数。结果强烈支持缩放假设，即使是相当短的链，确认它确实是可能的，以给出一个准确的通用描述的模拟模型，不同的许多细节。
Coarse-grained theories of dense polymer liquids such as block copolymer melts predict a universal dependence of equilibrium properties on a few dimensionless parameters. For symmetric diblock copolymer melts, such theories predict a universal dependence on only chi N and (N) over bar, where chi is an effective interaction parameter, N is the degree of polymerization, and (N) over bar is a measure of overlap. We test whether simulation results for the structure factor S(q) obtained from several different simulation models are consistent with this two-parameter scaling hypothesis. We compare results from three models: (1) a lattice Monte Carlo model, the bond-fluctuation model, (2) a bead-spring model with harsh repulsive interactions, similar to that of Kremer and Grest, and (3) a bead-spring model with very soft repulsion between beads, and strongly overlapping beads. We compare results from pairs of simulations of different models that have been designed to have matched values of (N) over bar, over a range of values of chi N and N, and devise methods to test the scaling hypothesis without relying on any prediction for how the phenomenological interaction parameter chi depends on more microscopic parameters. The results strongly support the scaling hypothesis, even for rather short chains, confirming that it is indeed possible to give an accurate universal description of simulation models that differ in many details.