Towards the control of surface properties via nanostructured polymeric materials

该研究项目侧重于研究末端接枝的带电聚合物在水介质中的动态表面力(摩擦力、粘附力、表面力的时间和距离相关性)。表面力仪器(SFA)将直接测量表面性质，这是直接测量表面之间作用力的最可靠的仪器之一。虽然过去已经对不同类型的聚合物轴承表面进行了一些使用SFA的研究，但其润滑和粘着机理还没有被清楚地阐明。缺乏系统地研究聚合物性质和环境条件对表面相互作用的影响，部分原因是难以控制聚合物在云母上的接枝密度和接枝层的稳定性，云母是SFA测量最可靠的衬底。我们最近开发了不同的方法，允许聚合物通过控制接枝密度直接共价连接到等离子激活的云母表面。我们建议使用两嵌段共聚物(疏水/可电离嵌段)共价连接到云母衬底上，最内层的疏水层直接连接到云母上，而可电离聚合物作为最外层悬挂在水介质中。疏水嵌段将在聚合物/云母界面作为防止水解反应的保护层，这可能是聚合物解离或滑移的位置。通过这些方法，我们的目标是在端接枝聚合物层的物理和化学性质(厚度、接枝密度、电离度、弹性、表面粗糙度、化学官能度)、环境条件(离子强度、pH、温度、溶剂条件、压缩、剪切)和含聚合物表面之间的表面相互作用(摩擦、粘合和力的距离依赖关系)之间建立可靠的关联。

The research program focuses on the investigation of dynamic surface forces (friction, adhesion, time- and distance-dependence of the surface forces) of end-grafted charged polymers in aqueous media. The surface properties will be directly measured using a Surface Forces Apparatus (SFA), being one of the most reliable instruments for the direct measurement of molecular forces acting between surfaces. Although several studies using SFA have been carried out in the past for different classes of polymer-bearing surfaces, the lubrication and adhesion mechanisms are not clearly elucidated. The lack of systematic studies examining the influence of polymer properties and environmental conditions on the surface interactions is in part a result of the difficulty in controlling the polymer grafting density and the stability of grafted layers on mica, which is the most reliable substrate for SFA measurements. We have recently developed different approaches allowing direct covalent attachment of polymers onto plasma activated mica surfaces with a control in the grafting density. We propose to use diblock copolymers (hydrophobic/ionizable block) covalently attached to mica substrates with an innermost hydrophobic layer directly bond to mica and the ionizable polymers as the outermost layer dangling in aqueous media. The hydropbobic block will act as a protective layer against hydrolysis reactions at the polymer/mica interface, a likely location for polymer cleavage or slip. With these approaches, we aim to establish reliable correlations between physical and chemical properties of the end-grafted polymer layers (thickness, grafting density, degree of ionization, elasticity, surface roughness, chemical functionality), environmental conditions (ionic strength, pH, temperature, solvent condition, compression, shear) and surface interactions (friction, adhesion and distance-dependence of the forces) between polymer-bearing surfaces.