Nonlinear Vibrational Probes of Structure at Charged Polymer-Aqueous Interfaces

聚合物被用来生产我们日常生活中遇到的许多物品，从汽车保险杠到洗发水瓶再到牙科填充物。虽然这些材料的主体属性进行了调整，使其变得坚硬或柔韧、透明或不透明，但同样关注的是调整它们的表面属性，以最好地与其预期的环境交互。例如，丙烯酸等材料因其坚固和轻便而被广泛用于制造医疗植入物，但它们的表面并不自然地具有生物兼容性。 将聚合物表面暴露在一种称为等离子体的电离气体中，是科学家改善丙烯酸和体内蛋白质之间相互作用的一种方法。但聚合物表面的性质并不是调节环境相互作用的唯一因素：与任何材料接触的水分子具有与主体水明显不同的性质。因此，水包围蛋白质的方式与聚合物表面几纳米、几十纳米到数百纳米远以及在主体水相中的方式有很大的不同。因此，了解聚合物表面如何与水相互作用对于开发表面结构和附着过程的整体视图至关重要。 在提出的方案中，我们使用高功率可见光和红外激光来探测高压等离子体处理后聚合物表面发生的微观变化。然后，我们跟踪水分子在处理前后与表面相互作用的变化，以更好地了解聚合物的润湿特性是如何改变的。以后的项目将引入氨基酸、多肽和蛋白质等生物分子来表征它们的吸附结构，并巩固我们对这些复杂但基本的分子相互作用的理解。这一领域继续受到泛化的阻碍，例如期望球形蛋白质在疏水表面变性。过去50年提供了许多不是这样的例子，表明需要从分子层面详细了解表面相互作用，从底物和溶剂开始。 这一领域的研究对生物医学工程师来说很重要，因为它为下一代医疗植入涂层和表面处理提供了指导，或者为改进现有的涂层和表面处理提供了想法。聚合物表面电荷改性在纺织加工中非常重要，因为经过等离子体处理的纤维可以增加对染料的粘附性，从而大大减少或消除对工人和环境有害的溶剂的需求。研究带电聚合物表面还有助于更好地理解轻质绝缘子如何经受风化，以便向加拿大城镇可靠地进行架空电力分配。一路走来，我们在这方面的工作为下一代科学家和工程师提供了许多培训机会。

Polymers are used to produce many of the objects we encounter in our daily life, from car bumpers to shampoo bottles to dental fillings. While the bulk properties of these materials are tuned to make them stiff or pliable, transparent or opaque, an equal amount of attention goes into tailoring their surface properties to best interact with their intended surroundings. For example, materials such as acrylic are widely used in creating medical implants as they are strong and lightweight, but their surfaces are not naturally biocompatible. Exposing the polymer surface to an ionized gas called a plasma is one method by which scientists improve the interaction between acrylic and proteins in the body. But the nature of the polymer surface is not the sole contributor to mediating environmental interactions: water molecules in contact with any material have markedly different properties from bulk water. As a result, the way in which water surrounds proteins is vastly different a few nanometers from the polymer surface, tens to hundreds of nanometers away, and in the bulk water phase. Understanding how the polymer surface interacts with water is therefore critical to developing a holistic view of surface structure and adhesion processes. In the proposed program, we use high power visible and infrared lasers to probe microscopic changes that occur on the polymer surface in response to high-voltage plasma treatment. We then follow the change in how water molecules interact with the surface before and after treatment to better understand how the wetting characteristics of the polymer have been altered. Later projects will introduce biological molecules such as amino acids, peptides and proteins to characterize their adsorbed structure, and solidify our understanding of these complex but fundamental molecular interactions. The field continues to be hindered by generalizations such as the expectation for globular proteins to denature on hydrophobic surfaces. The past five decades have provided many examples where this is not true, pointing to the need for a detailed molecular-level understanding of surface interactions, starting with the substrate and the solvent. Research in this area is important to biomedical engineers as it provides guidance for the next generation of medical implant coatings and surface treatments, or ideas for improving existing ones. Polymer surface charge modification is important in textile processing, as plasma-treated fibres have increased adhesion to dyes, dramatically reducing or eliminating the need for solvents that are harmful for workers and the environment. Studying charged polymer surfaces also leads to improved understanding of how lightweight insulators withstand weathering for reliable overhead power distribution to Canadian towns and cities. Along the way, our work in this area provides many training opportunities for the next generation of scientists and engineers.