Strong physical gels derived from thermoplastic elastomeric ABA triblock copolymers solvated with a midblock-selective oil continue to find use in increasingly diverse applications requiring highly elastic and mechanically robust soft materials with tunable properties. In this study, we first investigate the morphological characteristics of thermoplastic elastomer gels (TPEGs) derived from a homologous series of linear A(BA)_n multiblock copolymers composed of styrene and hydrogenated isoprene repeat units and possessing comparable molecular weight but varying in the number of B-blocks: 1 (triblock), 2 (pentablock), and 3 (heptablock). Small-angle X-ray scattering performed at ambient temperature confirms that (i) increasing hydrogenation reduces the microdomain periodicity of the neat copolymers and (ii) increasing the oil concentration of the TPEGs tends to swell the nanostructure (increasing the periodicity), but concurrently decreases the size of the styrenic micelles, to different extents depending on the molecular architecture. Complementary dissipative particle dynamics simulations reveal the level to which midblock bridging, which is primarily responsible for the elasticity in this class of materials, is influenced by both oil concentration and molecular architecture. Since constrained topological complexity increases with increasing block number, we introduce a midblock conformation index that facilitates systematic classification of the different topologies involved in nearest-micelle bridge formation. Those possessing at least one bridged and one looped midblock with no dangling ends are found to be the most predominant topologies in the pentablock and heptablock networks.

中文翻译：

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多嵌段共聚物凝胶中的微相分离形态和分子网络拓扑

由热塑性弹性体ABA三嵌段共聚物与中嵌段选择性油溶剂化而成的坚固的物理凝胶继续用于越来越多的应用中，这些应用需要具有可调性的高弹性和机械坚固的软质材料。在这项研究中，我们首先研究源自线性A（BA）_n同源序列的热塑性弹性体凝胶（TPEG）的形态特征由苯乙烯和氢化异戊二烯重复单元组成的多嵌段共聚物，具有相当的分子量，但B嵌段的数量不同：1（三嵌段），2（五嵌段）和3（七嵌段）。在环境温度下进行的小角度X射线散射证实（i）增加氢化作用会降低纯共聚物的微区周期性，并且（ii）增加TPEGs的油浓度会使纳​​米结构膨胀（增加周期性），但同时取决于分子结构，在不同程度上减小了苯乙烯胶束的尺寸。互补的耗散粒子动力学模拟揭示了中间嵌段桥接的水平，中间嵌段桥接主要负责此类材料的弹性，受油浓度和分子结构的影响。由于受约束的拓扑复杂性会随着块数的增加而增加，因此我们引入了中块构象索引，该索引有助于对最近胶束桥形成中涉及的不同拓扑进行系统的分类。在五嵌段和七嵌段网络中，那些具有至少一个桥接的和一个环状的中间嵌段且没有悬空末端的化合物被认为是最主要的拓扑。