Colloidal Polymer Chains: Construction, Statics and Dynamics

胶体聚合物链：结构、静力学和动力学

• 批准号: 0730780
• 负责人: Ralph Colby
• 金额: --
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0730780&HistoricalAwards=false
• 关键词: Colloidal; Polymer; Chains; Construction; Statics

PROPOSAL NO.: CBET - 0730780PRINCIPAL INVESTIGATOR: COLBY, RALPH HINSTITUTION: PENNSYLVANIA STATE UNIV UNIVERSITY PARKCOLLOIDAL POLYMER CHAINS: CONSTRUCTION, STATICS AND DYNAMICSFreely moving mammalian joints are lubricated by synovial fluid, consisting of 3 mg/mL hyaluronic acid (a high molar mass polyelectrolyte) and 20 mg/mL globular proteins. Natural synovial fluid has a typical friction coefficient of 0.002 to 0.010, compared with 0.010 to 0.050 for motor oil or physiological water without proteins. Recently, the PI's group has identified self-assembly of the globular proteins into chain-like aggregates as the source of considerable viscoelastic character in synovial fluid, which may account for the superb lubrication properties. The PIs plan to study such self-assembly in detail with biomimetic lubricating fluids made from self-assembled colloids with tunable interactions. In this way we seek to develop superior lubricants and other pragmatic fluids, while systematically studying the connections between interparticle interactions, aggregate structure and viscoelasticity. We plan to develop an 'artificial synovial fluid' (ASF) based on flexible string-like assemblies of 'colloidal atoms'. Atomic processes such as crystallization have been studied rigorously in the literature using colloidal particles, with the advantage of slower time scales and easier experimental observation. Fractal aggregates of colloids have also been studied in detail. However, because there has been no bottom-up assembly method to form long, flexible chains of colloids having rotatable 'bonds' between them, macromolecular systems have not been studied with 'colloidal polymers'. These are easily visualized and characterized chains of colloidal particles and will be constructed for studying macromolecular properties. In the depletion assembly method, depletion forces are used to hold colloids (e.g., polystyrene, PMMA) together. However, the key to the PIs technique is that two small flat regions are formed onto spherical colloids, at some specified angle. Since the region of depletant exclusion is much larger in the flat region than near the curved regions of the particles, the depletion force can be 10-100 times stronger when the flat regions face each other. The interaction strength along the polymer colloid chain (intra-'polymer' interactions) are thus mostly controlled in situ by changing the depletant concentration and flat region size, while the inter-polymer interactions are primarily controlled by only the depletant concentration. Thus, colloidal particles will be formed into chains with easily-tunable intra- and inter-polymer interactions. Moreover, depletion bonds are rotatable like true carbon-carbon bonds and reversible by changing solution depletant concentration. The fabrication of 'colloidal polymers' requires development of depletion assembly methods, and will enable us to examine many problems in polymer science with the assumptions made quite explicit. This research has three objectives. First, the PIs will construct ?colloidal polymers?. Spherical colloids with two flat regions will be prepared in the Penn State Nanofabrication Facility, and depletion assembly will be used to form flexible chains of colloidal particles, with controlled intra and inter-polymer interactions. They will, secondly, examine static properties. Chain size and conformation will be measured with video and confocal microscopy, and compared with predictions from classical polymer theory. Finally, they will examine dynamic properties. Rheology of the colloidal polymer chains will be studied as a function of chain length, concentration, intra- and inter-polymer interactions. Broader impact: The ability to have experimentally observable 'polymers' will expose assumptions in the study of polymer systems, and open new classes of observable phenomena. In addition, we will host a web site that shows photos and video of static and dynamic properties of colloidal polymers, for instructional purposes at both the collegiate and high school levels. Seeing the properties by eye will facilitate learning. The PhD student on this project will learn techniques from both polymer and colloid science, and assist with disseminating the information in conferences, in journals, and with pictures and movies on the website.

提案编号：CBET - 0730780 首席研究员：COLBY，RALPH HINSTUTION：宾夕法尼亚州立大学公园胶体聚合物链：结构、静态和动力学自由移动的哺乳动物关节由滑液润滑，滑液由 3 mg/mL 透明质酸（高摩尔质量聚电解质）和 20 mg/mL 球状蛋白。天然滑液的典型摩擦系数为 0.002 至 0.010，而不含蛋白质的机油或生理水的摩擦系数为 0.010 至 0.050。最近，PI 的研究小组发现，球状蛋白自组装成链状聚集体是滑液中相当大的粘弹性特征的来源，这可能是其卓越润滑性能的原因。 PI 计划利用由具有可调节相互作用的自组装胶体制成的仿生润滑液来详细研究这种自组装。通过这种方式，我们寻求开发优质的润滑剂和其他实用流体，同时系统地研究颗粒间相互作用、聚集结构和粘弹性之间的联系。我们计划开发一种基于“胶体原子”灵活的线状组件的“人造滑液”（ASF）。文献中已经使用胶体粒子对结晶等原子过程进行了严格研究，其优点是时间尺度较慢且实验观察更容易。胶体的分形聚集体也得到了详细研究。然而，由于还没有自下而上的组装方法来形成胶体之间具有可旋转“键”的长而柔性的链，因此尚未用“胶体聚合物”研究大分子系统。这些是易于可视化和表征的胶体颗粒链，可用于研究大分子特性。在消耗组装方法中，消耗力用于将胶体（例如聚苯乙烯、PMMA）固定在一起。然而，PI 技术的关键在于，以某个特定的角度在球形胶体上形成两个小的平坦区域。由于平坦区域中的耗尽排除区域比粒子的弯曲区域附近大得多，因此当平坦区域彼此面对时，耗尽力可以强10-100倍。因此，沿聚合物胶体链的相互作用强度（“聚合物”内相互作用）主要通过改变耗尽剂浓度和平坦区域尺寸来原位控制，而聚合物间相互作用主要仅由耗尽剂浓度控制。因此，胶体颗粒将形成具有易于调节的聚合物内和聚合物间相互作用的链。此外，耗尽键像真正的碳-碳键一样可旋转，并且通过改变溶液耗尽剂浓度可逆。 “胶体聚合物”的制造需要开发耗尽组装方法，并使我们能够通过非常明确的假设来研究聚合物科学中的许多问题。这项研究有三个目标。首先，PI 将构建“胶体聚合物”。具有两个平坦区域的球形胶体将在宾夕法尼亚州立大学纳米加工设施中制备，并且耗尽组装将用于形成胶体颗粒的柔性链，并具有受控的聚合物内和聚合物间相互作用。其次，他们将检查静态属性。链的大小和构象将通过视频和共焦显微镜进行测量，并与经典聚合物理论的预测进行比较。最后，他们将检查动态特性。将研究胶体聚合物链的流变性作为链长度、浓度、聚合物内和聚合物间相互作用的函数。更广泛的影响：通过实验观察“聚合物”的能力将揭示聚合物系统研究中的假设，并开辟新的可观察现象类别。此外，我们将主办一个网站，展示胶体聚合物静态和动态特性的照片和视频，用于大学和高中的教学目的。亲眼看到这些特性将有助于学习。该项目的博士生将学习聚合物和胶体科学的技术，并协助在会议、期刊以及网站上的图片和电影中传播信息。