So Jung Park, Tristan Myers, Vinson Liao and Arthi Jayaraman
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In this study, we investigate the phase behavior of symmetric A<small><sub><em>x</em></sub></small>B<small><sub><em>y</em></sub></small>A<small><sub><em>z</em></sub></small>B<small><sub><em>y</em></sub></small>A<small><sub><em>x</em></sub></small> and B<small><sub><em>x</em></sub></small>A<small><sub><em>y</em></sub></small>B<small><sub><em>z</em></sub></small>A<small><sub><em>y</em></sub></small>B<small><sub><em>x</em></sub></small> pentablock copolymers (pentaBCPs) where A and B monomers have the same statistical segment length. We use a combination of self-consistent field theory (SCFT) calculations and molecular dynamics (MD) simulations to link the polymer design parameters, namely the fraction of middle block volume to the volume of all blocks of same type, <em>τ</em>, overall volume fraction of A block, <em>f</em><small><sub>A</sub></small>, and segregation strength, <em>χN</em>, to the equilibrium morphologies and the distributions of chain conformations in these morphologies. In the phase diagrams calculated using SCFT, we observe broader double gyroid windows and the existence of lamellar morphologies even at small values <em>f</em><small><sub>A</sub></small> in contrast to what has been seen for diblock copolymers. We also see a reentrant phase sequence of double gyroid → cylinder → lamellae → cylinder → double gyroid with increasing <em>τ</em> at fixed <em>f</em><small><sub>A</sub></small>. The chain conformations adopted in these morphologies are sampled in coarse-grained MD simulations and quantified with distributions of the chain end-to-end distance and fractions of chains whose middle (A or B) and end (A or B) blocks remain within domains of same chemistry (A or B). These analyses show that the pentaBCP chains adopt “looping”, “bridging”, and “hybrid” (both looping and bridging) conformations, with a majority of the chains adopting the hybrid conformation. The spatial distributions for each of the blocks in the pentaBCPs show that blocks of the same type in a chain locally segregate within the same domains, with shorter blocks segregating towards the domain boundaries and longer blocks filling the domain interior. This combined SCFT-MD approach enables us to rapidly screen the extensive pentaBCP design space to identify design rules for transport-favorable morphologies as well as verify the chain conformations and spatial arrangements associated with the theory predicted reentrant phase behavior.</p>","PeriodicalId":91,"journal":{"name":"Molecular Systems Design & Engineering","volume":" 12","pages":" 1235-1253"},"PeriodicalIF":3.2000,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/me/d4me00138a?page=search","citationCount":"0","resultStr":"{\"title\":\"Self-consistent field theory and coarse-grained molecular dynamics simulations of pentablock copolymer melt phase behavior†\",\"authors\":\"So Jung Park, Tristan Myers, Vinson Liao and Arthi Jayaraman\",\"doi\":\"10.1039/D4ME00138A\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p >Block copolymer (BCP) self-assembly leads to nanostructured materials with diverse ordered morphologies, some of which are attractive for transport applications. 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We use a combination of self-consistent field theory (SCFT) calculations and molecular dynamics (MD) simulations to link the polymer design parameters, namely the fraction of middle block volume to the volume of all blocks of same type, <em>τ</em>, overall volume fraction of A block, <em>f</em><small><sub>A</sub></small>, and segregation strength, <em>χN</em>, to the equilibrium morphologies and the distributions of chain conformations in these morphologies. In the phase diagrams calculated using SCFT, we observe broader double gyroid windows and the existence of lamellar morphologies even at small values <em>f</em><small><sub>A</sub></small> in contrast to what has been seen for diblock copolymers. We also see a reentrant phase sequence of double gyroid → cylinder → lamellae → cylinder → double gyroid with increasing <em>τ</em> at fixed <em>f</em><small><sub>A</sub></small>. 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引用次数: 0
摘要
嵌段共聚物(BCP)的自组装可产生具有多种有序形态的纳米结构材料,其中一些对传输应用具有吸引力。与二嵌段共聚物相比,多嵌段 AB 共聚物具有更大的设计参数空间,允许研究人员定制自组装以实现目标形态,因此备受关注。在本研究中,我们研究了对称的 AxByAzByAx 和 BxAyBzAyBx 五嵌段共聚物(pentaBCPs)的相行为,其中 A 和 B 单体具有相同的统计段长度。我们采用自洽场理论(SCFT)计算和分子动力学(MD)模拟相结合的方法,将聚合物设计参数(即中间嵌段体积占同类所有嵌段体积的比例τ、A 嵌段的总体积分数 fA 和偏析强度 χN)与平衡形态以及这些形态中的链构象分布联系起来。在使用 SCFT 计算的相图中,我们观察到了更宽的双陀螺窗口,甚至在 fA 值较小时也存在片状形态,这与二嵌段共聚物的情况截然不同。我们还发现,在固定的 fA 值下,随着 τ 的增大,会出现双陀螺→圆柱→薄片→圆柱→双陀螺的重入相序列。在粗粒度 MD 模拟中对这些形态所采用的链构象进行了采样,并通过链端到端距离的分布以及中间(A 或 B)和末端(A 或 B)块保持在相同化学性质(A 或 B)域内的链的分数进行了量化。这些分析表明,pentaBCP 链采用了 "循环"、"桥接 "和 "混合"(循环和桥接)构象,其中大多数链采用了混合构象。pentaBCP 链中每个嵌段的空间分布显示,链中相同类型的嵌段会局部分离到相同的结构域中,较短的嵌段分离到结构域边界,较长的嵌段则填充到结构域内部。这种 SCFT-MD 组合方法使我们能够快速筛选广泛的 pentaBCP 设计空间,从而确定有利于传输的形态设计规则,并验证与理论预测的重入相行为相关的链构象和空间排列。
Self-consistent field theory and coarse-grained molecular dynamics simulations of pentablock copolymer melt phase behavior†
Block copolymer (BCP) self-assembly leads to nanostructured materials with diverse ordered morphologies, some of which are attractive for transport applications. Multiblock AB copolymers are of interest as they offer a larger design parameter space than diblock copolymers allowing researchers to tailor their self-assembly to achieve target morphologies. In this study, we investigate the phase behavior of symmetric AxByAzByAx and BxAyBzAyBx pentablock copolymers (pentaBCPs) where A and B monomers have the same statistical segment length. We use a combination of self-consistent field theory (SCFT) calculations and molecular dynamics (MD) simulations to link the polymer design parameters, namely the fraction of middle block volume to the volume of all blocks of same type, τ, overall volume fraction of A block, fA, and segregation strength, χN, to the equilibrium morphologies and the distributions of chain conformations in these morphologies. In the phase diagrams calculated using SCFT, we observe broader double gyroid windows and the existence of lamellar morphologies even at small values fA in contrast to what has been seen for diblock copolymers. We also see a reentrant phase sequence of double gyroid → cylinder → lamellae → cylinder → double gyroid with increasing τ at fixed fA. The chain conformations adopted in these morphologies are sampled in coarse-grained MD simulations and quantified with distributions of the chain end-to-end distance and fractions of chains whose middle (A or B) and end (A or B) blocks remain within domains of same chemistry (A or B). These analyses show that the pentaBCP chains adopt “looping”, “bridging”, and “hybrid” (both looping and bridging) conformations, with a majority of the chains adopting the hybrid conformation. The spatial distributions for each of the blocks in the pentaBCPs show that blocks of the same type in a chain locally segregate within the same domains, with shorter blocks segregating towards the domain boundaries and longer blocks filling the domain interior. This combined SCFT-MD approach enables us to rapidly screen the extensive pentaBCP design space to identify design rules for transport-favorable morphologies as well as verify the chain conformations and spatial arrangements associated with the theory predicted reentrant phase behavior.
期刊介绍:
Molecular Systems Design & Engineering provides a hub for cutting-edge research into how understanding of molecular properties, behaviour and interactions can be used to design and assemble better materials, systems, and processes to achieve specific functions. These may have applications of technological significance and help address global challenges.