The morphology and chain packing structures in block copolymers strongly impact their mechanical response; therefore, to design and develop high performance materials that utilize block copolymers, it is imperative to have an understanding of their self-assembly behavior. In this research, we utilize coarse-grained (CG) molecular dynamics to study the effects of peptidic volume fraction and secondary structure on the morphological development and chain assembly of the triblocks poly(γ-benzyl-l-glutamate)-b-poly(dimethylsiloxane)-b-poly(γ-benzyl-l-glutamate) (GSG) and poly(dimethylsiloxane)-b-poly(γ-benzyl-l-glutamate)-b-poly(dimethylsiloxane) (SGS). This necessitated developing a complete coarse-grained parameter set for poly(dimethylsiloxane) that closely captures the radial pair distribution of a united atom model and the experimental density at 300 K. These parameters are combined with the MARTINI amino acid CG force field and validated against prior reported values of domain spacing and peptide chain packing for GSG. The combined CG parameter set is then used to model SGS, a triblock currently in development for nature-inspired mechanically enhanced hybrid materials. The results reveal that the peptide side chain strongly influences the final morphology. For instance, lamellar or hexagonally packed cylindrical domain formation can result from the variation in side-chain interactions, namely, side-chain sterics preventing curved interface formation by increasing interfacial free volume. Ultimately, this research lays the foundation for future studies involving systems with dispersity, mixtures of secondary structures, and larger multiblock copolymers, such as polyurethanes and polyureas.

中文翻译：

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肽/ PDMS三嵌段形态的粗粒度建模

嵌段共聚物的形态和链堆积结构强烈影响其机械响应。因此，要设计和开发利用嵌段共聚物的高性能材料，必须了解其自组装行为。在这项研究中，我们利用粗粒（CG）分子动力学研究肽的体积分数和二级结构对三嵌段聚（γ-苄基-1-谷氨酸）-b-聚（二甲基硅氧烷）-b-聚（γ-苄基-1-谷氨酸）（GSG）和聚（二甲基硅氧烷）-b-聚（γ-苄基-1-谷氨酸）-b-聚（二甲基硅氧烷）（SGS）。这就需要为聚二甲基硅氧烷开发一个完整的粗粒度参数集，该参数集应紧密捕获一个统一原子模型的径向对分布以及在300 K时的实验密度。这些参数与MARTINI氨基酸CG力场结合在一起并进行了验证先前报道的GSG的域间距和肽链堆积值。然后，将组合的CG参数集用于建模SGS，SGS是目前正在开发的，受自然启发的机械增强混合材料的三嵌段共聚物。结果表明，肽侧链强烈影响最终的形态。例如，层状或六角形堆积的圆柱状结构域的形成可能是由于侧链相互作用的变化所致，即 侧链空间通过增加界面自由体积来防止弯曲界面的形成。最终，这项研究为涉及具有分散性，二级结构混合物和较大的多嵌段共聚物（例如聚氨酯和聚脲）的体系的未来研究奠定了基础。