In Situ Tracking of Composition and Morphology of a Diblock Copolymer Film with GISAXS during Exchange of Solvent Vapors at Elevated Temperatures
In Situ Tracking of Composition and Morphology of a Diblock Copolymer Film with GISAXS during Exchange of Solvent Vapors at Elevated Temperatures
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DOI：
10.1002/adfm.201706226
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发表时间：
2018-05-09
影响因子：
19
通讯作者：
Papadakis, Christine M.
中科院分区：
文献类型：
--
作者：
Berezkin, Anatoly V.;Jung, Florian;Papadakis, Christine M.
在高温下的溶剂热蒸气退火应用于由圆柱形聚苯乙烯-嵌段-聚（二甲基硅氧烷）（PS-b-PDMS）二嵌段共聚物形成的薄膜。此时，薄膜在正庚烷蒸气中膨胀（对PDMS具有高度选择性）。该蒸气逐步被甲苯蒸气替代（对PS的选择性弱）。使用原位，实时掠入射小角X射线散射（GISAXS）的形态进行了研究。最初的圆柱形形态转变为，除其他外，层状的。这种新型的实验允许探测PS-b-PDMS/正庚烷/甲苯混合物的状态图中的轨迹。为了证实的形态，它们产生的分子模拟，和2D GISAXS地图使用扭曲波玻恩近似计算。为了将形态与两种类型的纳米畴中的溶剂分布相关联，后者是从2D GISAXS图中的布拉格反射的强度与膜的溶胀比沿着来估计的。与在室温下进行的类似实验的结果进行比较，结果在相同的序列的形态，但是，在高温下，得到更有序的结构。这种新的方法被证明是有效的，以实现具有所需的形态和取向的嵌段共聚物薄膜。
Solvothermal vapor annealing at elevated temperature is applied to a thin film from a cylinder-forming polystyrene-block-poly(dimethyl siloxane) (PS-b-PDMS) diblock copolymer. At this, the film is swollen in the vapor of n-heptane (highly selective for PDMS). This vapor is stepwise replaced by the vapor of toluene (weakly selective for PS). The morphologies are investigated using in situ, real-time grazing-incidence small-angle X-ray scattering (GISAXS). The initial cylindrical morphology is transformed into, among others, the lamellar one. This novel type of experiments allows probing a trajectory in the state diagram of the PS-b-PDMS/n-heptane/toluene mixture. To corroborate the morphologies, they are generated by molecular simulations, and the 2D GISAXS maps are calculated using the distorted-wave Born approximation. To relate the morphologies to the solvent distribution in the two types of nanodomains, the latter is estimated from the intensities of the Bragg reflections in the 2D GISAXS maps along with the swelling ratio of the film. Comparison with the results from a similar experiment carried out at room temperature results in the same sequence of morphologies; however, at elevated temperature, more well-ordered structures are obtained. This new approach proves to be efficient to achieve a block copolymer thin film having a desired morphology and orientation.