Brush Gels: Where Theory, Simulations, and Experiments Meet
Brush Gels: Where Theory, Simulations, and Experiments Meet
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DOI：
10.1021/acs.macromol.2c01149
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发表时间：
2022-08-18
期刊：
影响因子：
5.5
通讯作者：
Dobrynin, Andrey V.
中科院分区：
文献类型：
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作者：
Jacobs, Michael;Vashahi, Foad;Dobrynin, Andrey V.
具有刷子状（梳状或瓶刷状）链的聚合物网络具有类似生物组织的机械特性，并且可以膨胀到比线性链更大的体积。我们结合了Flory-Rehner方法、尺度分析、分子动力学模拟和实验数据，研究了在甲苯中膨胀的聚丙烯酸正丁酯（PBA）网络，以阐明刷链结构对平衡膨胀比Q（eq）、膨胀凝胶的模量G(gel)（Q(eq)）的影响，以及它与干燥网络的非线性模量G（Q(eq)）的关系。PBA凝胶的模拟数据和实验结果分析表明，随着平衡溶胀比的增加，凝胶剪切模量单调降低，G(G)(el)（Q(eq)）与Q(eq)（-3）成正比，符合类theta-solvent的溶胀行为。聚合度n（sc）和侧链接枝密度1/ng对凝胶模量有显著影响，表现为具有相同溶剂含量的机械不同的凝胶。这种独特的行为是由凝胶状态下侧链的膨胀引起的刷股结构控制的硬化来解释的。在标度模型的框架下，膨胀链的有效库恩长度b K可以用干燥状态下的库恩长度b(K)（,s）和在Flory-Rehner方法框架下计算的剪切模量G(gel)(FR)(Q(eq)) = G(Q(eq))/Q(eq)（1/3）与凝胶模量G(gel)（Q(eq)）的比值来表示，使得b（K,s）近似于b(K)G(gel)(FR)(Q(eq))/G(gel)（Q(eq)）。从这一分析中得到的库恩长度突出了电刷刚度膨胀的不同机制。
Polymer networks with brush-like (comb or bottlebrush) strands can have mechanical properties similar to biological tissues and can swell to larger volumes than their linear chain counterparts. We use a combination of the Flory-Rehner approach, scaling analysis, molecular dynamics simulations, and experimental data for poly(n-butyl acrylate) (PBA) networks swollen in toluene to elucidate the effect of brush strand architecture on the equilibrium swelling ratio, Q(eq), the modulus of the swollen gel, G(gel)(Q(eq)), and its relationship with the nonlinear modulus of the dry network, G(Q(eq)). Analysis of simulation data and experimental results for PBA gels demonstrates that the gel shear modulus monotonically decreases with increasing equilibrium swelling ratio as G(g)(el)(Q(eq)) proportional to Q(eq)(-3), which is consistent with a theta-solvent-like swelling behavior. There is a significant effect of the degree of polymerization n(sc) and grafting density 1/ng of the side chains on the gel modulus that manifests as mechanically diverse gels with the same solvent content. This unique behavior is explained by the architecture-controlled stiffening of the brush strands due to the swelling of the side chains in the gel state. In the framework of a scaling model, the effective Kuhn length of the swollen strands, b K can be expressed in terms of the Kuhn length in the dry state, b(K)(,s), and the ratio of shear modulus calculated in the framework of the Flory-Rehner approach, G(gel)(FR)(Q(eq)) = G(Q(eq))/Q(eq)(1/3), to the gel modulus G(gel)(Q(eq)) such that b(K,s) approximate to b(K,s) approximate to b(K)G(gel)(FR)(Q(eq))/G(gel)(Q(eq)). The Kuhn length obtained from this analysis highlights different mechanisms of swollen brush rigidity.