In this study, we investigated the mechanism by which the microphase structure of polyurethane (PU), manipulated by the chemical composition, determines its macroscopic mechanical properties. Increasing the hard segment content induced a microphase transition from globular to elongated to bicontinuous. This transition significantly altered the mechanical behavior of PU from hyperelastic to elasto-plastic. This enhancement in the mechanical properties was related to the load-transfer capacity of the hard domains in each microphase. In the globular phase, most of the strain energy was absorbed by the soft matrix, limiting the contribution of the hard phase to the mechanical properties. Conversely, elongated discontinuous structures facilitated a homogeneous strain distribution during tension, promoting an immediate load transfer to the hard domain. To quantitatively evaluate the load-transfer efficiency, a mechanical model in which one soft hyperelastic spring was coupled to two rigid elasto-plastic springs was considered. The effects of the microphase morphology and hard domain dissociation on the load-transfer capability were identified. This study contributes to a molecular-level understanding of the deformation behavior and mechanical response of microphase-separated PU.

中文翻译：

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聚氨酯微相依赖性载荷传递能力的分子尺度研究


在这项研究中，我们研究了聚氨酯 （PU） 的微相结构受化学成分操纵，决定其宏观机械性能的机制。增加硬链段含量诱导了从球状到细长再到双连续的微相转变。这种转变显着改变了 PU 的机械行为，从超弹性变为弹塑性。机械性能的这种增强与每个微相中硬畴的载荷传递能力有关。在球状相中，大部分应变能被软基体吸收，限制了硬相对机械性能的贡献。相反，细长的不连续结构促进了张力过程中的均匀应变分布，促进了载荷立即转移到硬域。为了定量评估载荷传递效率，考虑了一个机械模型，其中一个软超弹性弹簧耦合到两个刚性弹塑性弹簧。确定了微相形态和硬结构域解离对载荷传递能力的影响。这项研究有助于从分子水平上理解微相分离的 PU 的变形行为和机械响应。