Parameswar Ashray V, Dikshit Karan V, Movafaghi Sanli, Bruns Carson J, Goodwin Andrew P
ACS Appl Mater Interfaces. 2021 Jan 13;13(1):1486-1492. doi: 10.1021/acsami.0c18432. Epub 2020 Dec 28.
This work reports the development of a mechanochemistry activated covalent conjugation (MACC) reaction that shows areas of interfacial failure in soft hydrogels. Hydrogels are prone to delamination from rigid substrates due to the competition between swelling and adhesion, which can lead to bonding failure in a mechanism similar to crack propagation in harder materials. In this work, reductive amination was shown to occur when a ketone-bearing fluorescein derivative was bonded to an amine-functionalized hydrogel, as both of these moieties were found to be necessary for covalent conjugation into the gel network. For thin, circular polyacrylamide hydrogels, wrinkle patterns and regions of subsequent delamination at the edge of the gel were found to be selectively tagged by the dye. This reaction was then used to explore the effect of gel properties on patterns of interfacial failure. As cross-linker loading increased, the propagation of the delamination front and the area fraction of delamination were both found to increase, as shown by fluorescence images of gels. Increasing the thickness of the gel increased the fraction of delaminated area but did not change its propagation toward the center of the gel. This MACC reaction shows how mechanochemical reactions can be used for fluorescence tagging without incorporating mechanophores into the polymer gel matrix.
这项工作报道了一种机械化学活化共价共轭（MACC）反应的进展，该反应显示了软质水凝胶中的界面失效区域。由于溶胀和粘附之间的竞争，水凝胶容易从刚性基材上分层，这可能导致类似于硬质材料中裂纹扩展的机制中的粘结失效。在这项工作中，当含酮的荧光素衍生物与胺官能化水凝胶结合时，还原胺化反应发生，因为发现这两个部分对于共价共轭到凝胶网络中都是必需的。对于薄的圆形聚丙烯酰胺水凝胶，发现凝胶边缘的皱纹图案和随后分层的区域被染料选择性标记。然后利用该反应来探索凝胶性质对界面失效模式的影响。如凝胶的荧光图像所示，随着交联剂负载量的增加，分层前沿的扩展和分层的面积分数均增加。增加凝胶的厚度会增加分层面积的比例，但不会改变其向凝胶中心的扩展。这种MACC反应展示了机械化学反应如何用于荧光标记，而无需将机械发色团掺入聚合物凝胶基质中。
