Goodson Amy D, Rick Maxwell S, Troxler Jessie E, Ashbaugh Henry S, Albert Julie N L
Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States.
ACS Appl Polym Mater. 2022 Jan 14;4(1):327-337. doi: 10.1021/acsapm.1c01313. Epub 2021 Dec 15.
Block copolymers (BCPs) consist of two or more covalently bound chemically distinct homopolymer blocks. These macromolecules have emerging applications in photonics, membrane separations, and nanolithography stemming from their self-assembly into regular nanoscale structures. Theory suggests that cyclic BCPs should form features up to 40% smaller than their linear analogs while also exhibiting superior thin-film stability and assembly dynamics. However, the complex syntheses required to produce cyclic polymers mean that a need for pure cyclic BCPs would present a challenge to large-scale manufacturing. Here, we employ dissipative particle dynamics simulations to probe the self-assembly behavior of cyclic/linear BCP blends, focusing on nanofeature size and interfacial width as these qualities are critical to nanopatterning applications. We find that for mixtures of symmetric cyclic and linear polymers with equivalent lengths, up to 10% synthetic impurity has a minimal impact on cyclic BCP feature dimensions and interfacial roughness. On the other hand, blending with cyclic BCPs provides a route to "fine-tune" linear BCP feature sizes. We analyze simulated blend domain spacings within the context of strong segregation theory and find significant deviations between simulation and theory that arise from molecular-level packing motifs not included in theory. These insights into blend self-assembly will assist experimentalists in rationally designing BCP materials for advanced nanolithography applications.
嵌段共聚物（BCP）由两个或更多个通过共价键结合的化学性质不同的均聚物嵌段组成。这些大分子因其自组装成规则的纳米级结构而在光子学、膜分离和纳米光刻领域有着新兴的应用。理论表明，环状BCP形成的特征尺寸应比其线性类似物小40%，同时还表现出优异的薄膜稳定性和组装动力学。然而，生产环状聚合物所需的复杂合成方法意味着，对纯环状BCP的需求将给大规模制造带来挑战。在此，我们采用耗散粒子动力学模拟来探究环状/线性BCP共混物的自组装行为，重点关注纳米特征尺寸和界面宽度，因为这些性质对纳米图案化应用至关重要。我们发现，对于具有相同长度的对称环状和线性聚合物的混合物，高达10%的合成杂质对环状BCP的特征尺寸和界面粗糙度影响极小。另一方面，与环状BCP共混为“微调”线性BCP的特征尺寸提供了一条途径。我们在强分离理论的背景下分析了模拟的共混物域间距，发现模拟结果与理论之间存在显著偏差，这是由理论中未包含的分子水平堆积模式引起的。这些对共混物自组装的见解将有助于实验人员合理设计用于先进纳米光刻应用的BCP材料。
