Lamellar microdomain orientation and phase transition of polystyrene-b-poly (methyl methacrylate) films by controlled interfacial interactions
Lamellar microdomain orientation and phase transition of polystyrene-b-poly (methyl methacrylate) films by controlled interfacial interactions
复制标题
DOI：
10.1039/c2sm07297a
复制
发表时间：
2012-01-01
期刊：
影响因子：
3.4
通讯作者：
Russell, Thomas P.
中科院分区：
文献类型：
--
作者：
Choi, Seunghoon;Kim, Eunhye;Russell, Thomas P.
利用透射电子显微镜（TEM）和掠射小角x射线散射（GISAXS）研究了对称聚苯乙烯-b-聚甲基丙烯酸甲酯（PS-b-PMMA）薄膜在无规共聚物接枝基底上的层状微畴取向和相变。通过控制P（S-r-MMA）无规共聚物中苯乙烯摩尔分数（X-S），将底物上的界面相互作用从ps选择性调整为pmma选择性。除了X-S = 0.55的中性衬底外，所有薄膜都表现出平行的层状微畴取向，并通过TEM图像验证了这一点。然而，PS-b-PMMA薄膜的GISAXS分析表明，面外散射与面内散射的强度比可以作为评价片层微畴取向程度或衬底表面中性程度的敏感指标。PS-b-PMMA的膜厚和分子量影响了中性衬底上片层微畴的取向，这主要是由于链端效应和向列项竞争对自由能的熵贡献。有趣的是，PS-b-PMMA薄膜在一系列衬底上的有序-无序温度（ODT）在X-S = 0.55时达到最低点。ODT测量是一种评估衬底界面相互作用的新方法，证实了中性衬底诱导了衬底上PS和PMMA块之间的表面相容性。
The orientation of lamellar microdomains and phase transition for the thin films of a symmetric polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) on random copolymer-grafted substrates were investigated by transmission electron microscopy (TEM) and grazing-incidence small-angle X-ray scattering (GISAXS). The styrene mole fraction (X-S) in random copolymers of P(S-r-MMA) was controlled to tune the interfacial interactions at the substrates from PS-selective to PMMA-selective. Except in the case of a neutral substrate with X-S = 0.55, all the films showed the parallel orientations of lamellar microdomains, which were validated by the TEM images. However, the GISAXS analysis of PS-b-PMMA films indicated that the intensity ratio of the out-of-plane scattering to the in-plane scattering can be a sensitive indicator for evaluating the degree of orientation of lamellar microdomains or surface neutrality at the substrates. The orientation of lamellar microdomains on a neutral substrate was influenced by the film thickness and molecular weight of PS-b-PMMA, which results from predominantly the entropic contribution to the free energy in competition between the chain-end effect and nematic term. Intriguingly, the order-to-disorder temperature (ODT) of PS-b-PMMA films on a series of the substrates shows a minimum at X-S = 0.55. The ODT measurements, a new approach to evaluating the interfacial interactions at substrates, confirm that a neutral substrate induces surface compatibility between the PS and PMMA blocks at the substrate.