A mesoscale model for the micromechanical study of gels
A mesoscale model for the micromechanical study of gels
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DOI：
10.1016/j.jmps.2022.104982
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发表时间：
2022-06
影响因子：
5.3
通讯作者：
Robert J. Wagner;J. Dai;Xinfu Su;F. Vernerey
中科院分区：
文献类型：
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作者：
Robert J. Wagner;J. Dai;Xinfu Su;F. Vernerey
凝胶由被一些间隙溶剂溶胀的聚合物网络组成。由于它们在从粘合剂到组织工程等领域的广泛适用性，材料科学家和工程师正在对其进行广泛的研究。凝胶的机械性能极大地影响其在此类应用中的功效，并且很大程度上取决于其底层微观结构和成分尺度性能。然而，预测性地绘制凝胶的局部到整体特性函数仍然很困难，部分原因是溶质-溶剂相互作用引入的复杂性。我们在此介绍一种新颖的离散介观建模方法，该方法通过 Flory-Huggins 混合参数 χ 保留渗透压中局部溶质浓度相关的梯度。这里使用的模型的迭代复制了由遥爪交联星形聚合物制成的凝胶，并输入 χ、大分子单体分子量 (M w)、交联官能度 (f) 和制备的溶质浓度 (phi*) 作为其输入，所有这些都类似于实验人员的控制参数。在这里，我们演示了该方法如何在不存在唯象成对势的情况下捕获聚合物悬浮液的溶剂依赖性均质化 (χ≤ 0.5) 或相分离 (χ> 0.5)。然后，我们展示了其对 10k tetra-PEG 凝胶的凝胶拓扑、各向同性膨胀力学和单轴拉伸应力的准确从头开始预测。最后，我们使用该模型来预测多功能 PEG 凝胶在一定 M w 和 f 范围内的机械响应和失效趋势，同时调查所述趋势的微机械起源。该模型预测，对于相同基础链长度的凝胶，交联功能的增加会导致更高的初始链拉伸（在平衡溶胀状态下测量），这提高了模量和失效应力，但降低了失效应变和韧性。
Gels are comprised of polymer networks swelled by some interstitial solvent. They are under wide investigation by material scientists and engineers for their broad applicability in fields ranging from adhesives to tissue engineering. Gels’ mechanical properties greatly influence their efficacy in such applications and are largely dictated by their underlying microstructures and constituent-scale properties. Yet predictively mapping the local-to-global property functions of gels remains difficult due-in part-to the complexity introduced by solute-solvent interactions. We here introduce a novel, discrete mesoscale modeling method that preserves local solute concentration-dependent gradients in osmotic pressure through the Flory-Huggins mixing parameter, χ. The iteration of the model used here replicates gels fabricated from telechelically crosslinked star-shaped polymers and intakes χ, macromer molecular weight (M w), crosslink functionality (f), and as-prepared solute concentration (ϕ*) as its inputs, all of which are analogues to the control parameters of experimentalists. Here we demonstrate how this method captures solvent-dependent homogenization (χ≤ 0.5) or phase separation (χ> 0.5) of polymer suspensions in the absence of phenomenological pairwise potentials. We then demonstrate its accurate, ab initio prediction of gel topology, isotropic swelling mechanics, and uniaxial tensile stress for a 10k tetra-PEG gel. Finally, we use the model to predict trends in the mechanical response and failure of multi-functional PEG-based gels over a range of M w and f, while investigating said trends’ micromechanical origins. The model predicts that increased crosslink functionality results in higher initial chain stretch (as measured at the equilibrated swollen state) for gels of the same underlying chain length, which improves modulus and failure stress but decreases failure strain and toughness.