Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, United States.
J Phys Chem B. 2011 Oct 13;115(40):11575-80. doi: 10.1021/jp204682x. Epub 2011 Sep 22.
In this work, molecular dynamics simulations were performed to study a carboxybetaine methacrylate (CBMA) hydrogel under various swelling states. The water content in this study ranged from 28% to 91% of the total weight of the hydrogel. Three transitions of the CBMA hydrogel were observed as the water content increased. The first transition occurs when the water content increases from 33% to 37%. The observed kink in the self-diffusion coefficient of water indicates that the hydration of the polymer network of the hydrogel is saturated; the further added water is in a less confined state. The second transition was found to be related to the physical cross-links of the polymer network. As the water content rises to above 62%, the lifetime of the physical cross-links decreases significantly. This abrupt change in the lifetime indicates that the transition represents the equilibrium swelling state of the hydrogel. Finally, the third transition was observed when the water content goes above 81%. The significant increases in the bond and angle energies of the polymer network indicate that the hydrogel reaches its upper limit swelling state at this transition. These results are comparable to previously published experimental studies of similar zwitterionic hydrogels.
在这项工作中，进行了分子动力学模拟，以研究各种溶胀状态下的羧基甜菜碱甲基丙烯酸酯（CBMA）水凝胶。在这项研究中，水的含量占水凝胶总重量的 28%到 91%。随着水含量的增加，观察到 CBMA 水凝胶的三个转变。第一个转变发生在水含量从 33%增加到 37%时。观察到水的自扩散系数的拐点表明水凝胶的聚合物网络的水合作用达到饱和；进一步添加的水处于不太受限的状态。第二个转变与聚合物网络的物理交联有关。当水含量上升到 62%以上时，物理交联的寿命显著下降。这种寿命的突然变化表明，这种转变代表了水凝胶的平衡溶胀状态。最后，当水含量超过 81%时，观察到第三个转变。聚合物网络的键和角能的显著增加表明，在该转变处水凝胶达到其最大溶胀状态。这些结果与先前发表的类似两性离子水凝胶的实验研究相当。
