Collaborative Research: Control of interfacial thermodynamics and functionalization using branched and cyclic molecules

项目编号：CBET-0730692 / CBET-0731319首席研究员：Mark D. Foster / David T. wu大学/机构：阿克伦大学/科罗拉多矿产学院：合作研究：利用支链分子和环分子控制界面热力学和功能化这是与科罗拉多矿产学院CBET-0731319的合作项目。在许多应用和工艺中，控制不依赖于体性质的聚合物界面性质是至关重要的，可以通过功能化分子富集界面来实现。由于期望的官能团在界面上可能不受青睐，因此需要一种通用策略来促进这种富集。我们的目标是使用新颖的非线性链结构来创造一种热力学驱动力，将功能化分子带到界面上，而不依赖于界面寻找基团。福斯特的团队（U. Akron）已经证明，长链分支确实可以驱使聚合物靠近或远离界面。这些实验只与Wu（科罗拉多矿业学院）的平均场理论预测部分一致。此外，预测环分子可以产生与化学基团和多分散性无关的界面驱动力。研究人员将对含有环状分子的混合物进行首次测量。为了推进对体积和界面热力学的理解，将这一概念转化为有用的应用，他们将整合定义良好的分子合成（Quirk， UA），混合行为的实验测量（Foster），以及新理论的发展（Wu）。智力优势：将开发一种新的自洽场形式主义，用于在对（非平均场）水平上处理分子内和分子间的相互作用，以解释明确的拓扑效应以及化学基团效应和链构象之间的相互作用。预计非线性链共混物的关键物理问题是单体相互作用引起的膨胀/坍塌和拥挤。早期的目标将是解释现有的表面偏析数据和与支链混合物相关的体热力学。将首次利用中子反射法和表面增强拉曼光谱对环链共混物的界面偏析进行实验测量，并对整体热力学相互作用参数进行测量。这些数据将与有关支链共混物的新信息一起进行比较，并用于改进理论。通过阴离子聚合合成明确的支链分子和环状分子将使特别敏锐的比较。还将与具有商业前景的Grubbs催化剂开环聚合合成的含有多分散环链的共混物进行比较。为了证明我们的方法，他们将通过将表面避免极性基团连接到具有专门设计的非线性结构的分子上来实现聚合物表面的功能化。更广泛的影响：本研究实现的长支链和环状聚合物的热力学建模将适用于体积和表面流变改性添加剂的设计（例如润滑油和控制液滴形成或辅助加工），粘合剂和密封剂（例如硅氧烷材料），以及药物输送（例如枝状聚合物）。它也将适用于含有支链和环状聚合物的生物系统，如多糖和核酸。通过让研究生参加合作大学和国家实验室的研究活动，以及通过阿克伦大学REU计划的本科生，教育将与研究相结合。教师和研究生将与阿克伦全球聚合物学院一起准备视频模块，用于面向K-12学生的网络和课堂推广。这些模块将描述研究中的基本概念，例如分子混合和分离的原因，光和中子的散射如何揭示结构，以及拉曼光谱如何对表面成分敏感。

Proposal Number: CBET-0730692 / CBET-0731319 Principal Investigator: Mark D. Foster / David T. WuUniversity/Institution: University of Akron/Colorado School of MinesTitle: Collaborative Research: Control of Interfacial thermodynamics and functionalization using branched and cyclic molecules This is a collaborative project with CBET-0731319, Colorado School of Mines.Control of polymer interfacial properties independent of bulk properties is crucial in many applications and processes, and can be achieved by enrichment of the interface by functionalized molecules. Since desired functional groups may not be favored at the interface, a general strategy is needed for promoting this enrichment. Our goal is to use novel nonlinear chain architectures to create a thermodynamic driving force to bring functionalized molecules to an interface without relying on interface-seeking groups. Foster's group (U. Akron) has shown that long-chain branching can indeed drive a polymer to or away from an interface. These experiments are only in partial agreement with mean-field theory predictions by Wu (Colorado School of Mines). Cyclic molecules are moreover predicted to produce an interfacial driving force independent of chemical group and polydispersity. The investigators will make the first measurements on blends containing cyclic molecules. To advance the understanding of both bulk and interfacial thermodynamics needed to move this concept to useful applications, they will integrate synthesis of well-defined molecules (Quirk, UA), experimental measurement of blend behavior (Foster), and development of new theory (Wu).Intellectual merit: A new self-consistent field formalism will be developed to treat intra- and inter-molecular interactions at the pair (non-mean-field) level, to account for explicit topological effects as well as interplay between chemical group effects and chain conformation. The critical physical issues for blends of nonlinear chains are anticipated to be swelling/collapse and crowding due to monomer-monomer interactions. An early objective will be to explain existing data on surface segregation and related bulk thermodynamics for mixtures with branched chains. Experimental measurements of interfacial segregation with neutron reflectometry and surface enhanced Raman spectroscopy, as well as of the bulk thermodynamic interaction parameter, will be made on blends of cyclic chains for the first time. Together with new information on blends with branched chains, these data will be compared with and used to refine theory. Synthesis of well-defined branched and cyclic molecules by anionic polymerization will enable particularly incisive comparisons. Comparison will also be made with blends containing polydisperse cyclic chains synthesized using ring-opening polymerizations with a Grubbs catalyst that has commercial promise. To demonstrate our approach, they will functionalize a polymer surface with surface-avoiding polar groups by attaching them to molecules with specifically designed nonlinear architectures.Broader impacts: The thermodynamic modeling of long-branched and cyclic polymers enabled by this study will be applicable to the design of additives for bulk and surface rheology modification (e.g. in lubricant oils and to control droplet formation or aid processing), for adhesives and sealants (e.g. siloxane materials), and for drug delivery (e.g. dendronized polymers). It will also be applicable for biological systems containing branched and cyclic polymers such as polysaccharides and nucleic acids. Education will be integrated with research by having graduate students join in research activities at the partner university and national laboratories, and by including undergraduates through U. Akron's REU program. Faculty and graduate students will prepare video modules with the Akron Global Polymer Academy for web and classroom-based outreach to K-12 students. These modules will describe basic concepts from the research, such as reasons for the mixing and demixing of molecules, how scattering of light and neutrons revealsstructure,and how Raman spectroscopy can be sensitive to the composition of surfaces.