Hennessy Matthew G, Münch Andreas, Wagner Barbara
Mathematical Institute, University of Oxford, Andrew Wiles Building, Woodstock Road, Oxford OX2 6GG, United Kingdom.
Weierstrass Institute, Mohrenstrasse 39, 10117 Berlin, Germany.
Phys Rev E. 2020 Mar;101(3-1):032501. doi: 10.1103/PhysRevE.101.032501.
We present a full kinetic model of a hydrogel that undergoes phase separation during swelling and deswelling. The model accounts for the interfacial energy of coexisting phases, finite strain of the polymer network, and solvent transport across free boundaries. For the geometry of an initially dry layer bonded to a rigid substrate, the model predicts that forcing solvent into the gel at a fixed rate can induce a volume phase transition, which gives rise to coexisting phases with different degrees of swelling, in systems where this cannot occur in the free-swelling case. While a nonzero shear modulus assists in the propagation of the transition front separating these phases in the driven-swelling case, increasing it beyond a critical threshold suppresses its formation. Quenching a swollen hydrogel induces spinodal decomposition, which produces several highly localized, highly swollen phases which coarsen and are then ejected from free boundary. The wealth of dynamic scenarios of this system is discussed using phase-plane analysis and numerical solutions in a one-dimensional setting.
我们提出了一种水凝胶的完整动力学模型，该水凝胶在溶胀和脱溶胀过程中会发生相分离。该模型考虑了共存相的界面能、聚合物网络的有限应变以及溶剂在自由边界上的传输。对于初始干燥层粘结到刚性基底的几何形状，该模型预测，在自由溶胀情况下不会发生这种情况的系统中，以固定速率向凝胶中强制注入溶剂会引发体积相变，从而产生具有不同溶胀程度的共存相。虽然非零剪切模量有助于在驱动溶胀情况下分离这些相的转变前沿的传播，但将其增加到超过临界阈值会抑制其形成。对溶胀的水凝胶进行淬火会引发旋节线分解，产生几个高度局部化、高度溶胀的相，这些相粗化然后从自由边界喷出。使用一维设置中的相平面分析和数值解讨论了该系统丰富的动态情况。
