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.

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球状蛋白。天然滑液的典型摩擦系数为0.002至0.010，而没有蛋白质的机油或生理水为0.010至0.050。最近，PI组已将球状蛋白的自组装确定为链状聚集体是滑液中相当大的粘弹性特征的来源，这可能是造成精湛的润滑性能的。 PIS计划通过与可调相互作用的自组装胶体制成的仿生润滑流体进行详细研究这种自组装。通过这种方式，我们试图开发出色的润滑剂和其他务实的液体，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连接。我们计划基于“胶体原子”的柔性弦样组件来开发“人工滑液”（ASF）。在文献中，使用胶体颗粒对原子过程（例如结晶）进行了严格的研究，具有较慢的时间尺度和更容易的实验观察。还详细研究了胶体的分形聚集体。但是，由于没有自下而上的组装方法可以形成长时间的胶体链链，它们之间具有可旋转的“键”，因此尚未使用“胶体聚合物”研究大分子系统。这些易于可视化和表征胶体颗粒的链，并将用于研究大分子特性。在耗尽的组装方法中，耗尽力用于将胶体（例如聚苯乙烯，PMMA）固定在一起。但是，PIS技术的关键是将两个小的扁平区域以某个指定角度形成到球形胶体上。由于在平坦区域的消耗排除区域比粒子弯曲区域附近要大得多，因此当平坦区域彼此面对时，耗尽力的耗尽力可能会更强。因此，沿聚合物胶体链（内聚合物'相互作用）沿线的相互作用强度主要通过改变消耗浓度和扁平区域大小而在原位控制，而聚合物间相互作用仅由消耗剂浓度控制。因此，胶体颗粒将形成具有易于调节的链内和聚合物间相互作用的链。此外，耗尽键像真实的碳碳键一样旋转，并且可以通过改变溶液消耗浓度而可逆。 “胶体聚合物”的制造需要开发耗尽的装配方法，并将使我们能够以相当明确的假设来检查聚合物科学中的许多问题。这项研究有三个目标。首先，PI会构建？胶体聚合物？将在宾夕法尼亚州纳米制剂设施中制备带有两个平坦区域的球形胶体，并且将使用耗尽的组装来形成具有控制的内部内部和聚合物间相互作用的胶体颗粒的柔性链。其次，他们将检查静态特性。链的大小和构象将通过视频和共聚焦显微镜进行测量，并与经典聚合物理论的预测进行比较。最后，他们将检查动态属性。胶体聚合物链的流变学将根据链长，浓度，内部和聚合物间相互作用的函数进行研究。更广泛的影响：具有实验可观察到的“聚合物”的能力将在聚合物系统的研究中揭示假设，并开放可观察到的新型现象。此外，我们还将托管一个网站，该网站显示胶体聚合物的静态和动态特性的照片和视频，以便在大学和高中级别的教学目的。看到眼睛的特性将有助于学习。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。