报告时间：2019年1月14日 上午10:00

报告地点：航天航空学院教一楼第二会议室

报告题目：Marangoni-effect-assisted spreading of ultrathin hydrogel films

个人介绍：

洪伟博士，现任南方科技大学力学与航空航天工程系教授，博士生导师。洪伟本科和硕士毕业于清华大学，获工程力学和计算机科学与工程学士学位、固体力学硕士学位，2006年在美国哈佛大学获工程科学博士学位；2008年在哈佛大学做博士后研究结束后在美国爱荷华州立大学航空航天工程系执教，历任助理教授、副教授（终身教职）、教授。2015年在起日本北海道大学国际软物质中心兼职，历任副教授、教授。洪伟的研究领域包括固体力学、断裂力学、材料的微结构演化、和多物理场建模，近年来致力于软物质物理（特别是聚合物凝胶、超强超韧凝胶和柔性复合材料的理论模型构筑）、介电材料的力电耦合损伤、电活性和磁活性材料与智能结构、固体表面失稳和形貌演化等方向的研究。

报告内容：

After dripping onto a water surface, a drop of ethanol solution of poly(stearyl acrylate-co-acrylic acid) [P(SA-co-AAc)] spreads quickly to form a thin film due to the differential surface tension, i.e. the Marangoni effect. The solvent exchange from ethanol to water leads to the gelation of polymer solution which then turns into a hydrogel film. The spreading and formation of the gel films are influenced by both the molar fraction of SA f, and the polymer concentration of ethanol solution, C_P. The spreading is blocked at a high C_P, whereas the film iss fragmented when C_P is too low. At an intermediate C_P, the solution spreads at a constant speed, resulting in an ultrathin hydrogel film with uniform thickness. Here, we investigate the governing kinetics through a continuum model of the spreading and gelation process. It is found that both C_P and f influence the spreading process by tuning the surface tension of the ethanol solution and the viscoelasticity of the film, as suggested by our theoretical model. This work provided kinetic insights into the Marangoni phenomena of viscous polymer solutions. The strategy and principle should be applicable to other similar systems on the preparation of thin supramolecular gel films.