Vertical vs Lateral Macrophase Separation in Thin Films of Block Copolymer Mixtures: Computer Simulations and GISAXS Experiments.
Vertical vs Lateral Macrophase Separation in Thin Films of Block Copolymer Mixtures: Computer Simulations and GISAXS Experiments.
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DOI：
10.1021/acsami.6b16563
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发表时间：
2017-03
影响因子：
9.5
通讯作者：
A. V. Berezkin;Florian A. Jung;D. Posselt;Detlef-Matthias Smilgies;C. Papadakis
中科院分区：
文献类型：
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作者：
A. V. Berezkin;Florian A. Jung;D. Posselt;Detlef-Matthias Smilgies;C. Papadakis
两种长度非常不同的二嵌段共聚物的混合物可能具有宏观和微观相分离的特征;然而，关于二嵌段共聚物薄膜中的分离机制知之甚少。在目前的工作中，我们研究薄膜的混合物的两个组成对称的嵌段共聚物，无论是在单相和两相状态，结合粗粒分子模拟（耗散粒子动力学，DPD）与散射实验（掠入射小角度X射线散射，GISAXS）。我们发现，膜的厚度和选择性吸附的不同块的基板控制膜内的宏观相的分布，以及在其中的laminates的取向。在厚膜中，混合物在垂直方向上分成三层：两层富含短链共聚物的层形成在膜界面附近，而一层富含长链共聚物的层位于膜芯中。在富含短链共聚物的层中的层状取向由表面选择性决定，并且这种取向仅微弱地影响膜芯中层状结构的垂直取向。这提供了通过将嵌段共聚物与低分子添加剂混合来控制共聚物膜中的域取向的机会，而不是依赖于基底的更复杂的化学改性。在较薄的薄膜中，出现横向相分离。
Mixtures of two diblock copolymers of very different lengths may feature both macro- and microphase separation; however, not much is known about the mechanisms of separation in diblock copolymer thin films. In the present work, we study thin films of mixtures of two compositionally symmetric block copolymers, both in the one-phase and in the two-phase state, combining coarse-grained molecular simulations (dissipative particle dynamics, DPD) with scattering experiments (grazing-incidence small-angle X-ray scattering, GISAXS). We reveal that the film thickness and selective adsorption of different blocks to the substrate control the distribution of macrophases within the film as well as the orientation of the lamellae therein. In thick films, the mixtures separate in the vertical direction into three layers: Two layers being rich in short copolymers are formed near the film interfaces, whereas a layer being rich in long copolymers is located in the film core. The lamellar orientation in the layers rich in short copolymers is dictated by the surface selectivity, and this orientation only weakly affects the vertical orientation of lamellae in the film core. This provides the opportunity to control the domain orientation in the copolymer films by mixing block copolymers with low-molecular additives instead of relying on a more complicated chemical modification of the substrate. In thinner films, a lateral phase separation appears.