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

提案编号：CBET-0730692 / CBET-0731319主要研究者：Mark D.福斯特/大卫T.大学/机构：阿克伦大学/科罗拉多矿业学院题目：合作研究：界面热力学控制 这是与科罗拉多矿业学院CBET-0731319的合作项目。在许多应用和工艺中，独立于本体性质的聚合物界面性质的控制是至关重要的，并且可以通过由官能化分子富集界面来实现。由于所需的官能团在界面处可能不受欢迎，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的非线性链结构，以创建一个热力学驱动力，使功能化的分子的接口，而不依赖于接口寻求基团。 福斯特集团（U. Akron）已经表明，长链支化确实可以驱动聚合物到达或离开界面。这些实验只与吴（科罗拉多矿业学院）的平均场理论预测部分一致。此外，预测环状分子产生独立于化学基团和多分散性的界面驱动力。研究人员将对含有环状分子的混合物进行首次测量。为了推进对本体和界面热力学的理解，将这一概念应用于实际应用，他们将整合定义明确的分子的合成（Quirk，UA）、共混行为的实验测量（Foster）和新理论的发展（Wu）。一个新的自洽场形式主义将发展到处理内和分子间的相互作用在对（非平均场）水平，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。非线性链的共混物的关键物理问题预计是溶胀/塌陷和拥挤由于单体-单体相互作用。一个早期的目标将是解释现有的数据表面偏析和相关的散装热力学与支链的混合物。实验测量的界面偏析与中子反射仪和表面增强拉曼光谱，以及体热力学相互作用参数，将首次在环状链的共混物。连同新的信息共混物与支链，这些数据将进行比较，并用于完善理论。 通过阴离子聚合合成明确定义的支链和环状分子将使特别尖锐的比较成为可能。还将与含有多分散环状链的共混物进行比较，所述共混物使用具有商业前景的Grubbs催化剂使用开环聚合合成。为了展示我们的方法，他们将通过将表面回避极性基团连接到具有专门设计的非线性结构的分子上，使聚合物表面功能化。本研究所建立的长支化和环状聚合物的热力学模型可用于本体和表面流变改性添加剂的设计这些聚合物可用于粘合剂和密封剂（例如，硅氧烷材料）以及药物递送（例如，树枝状聚合物）。它也将适用于含有支链和环状聚合物如多糖和核酸的生物系统。教育将与研究相结合，让研究生参加合作大学和国家实验室的研究活动，并通过美国大学本科生。阿克伦的REU计划。教师和研究生将准备视频模块与阿克伦全球聚合物学院的网络和课堂为基础的推广到K-12学生。这些模块将描述研究中的基本概念，例如分子混合和分层的原因，光和中子的散射如何揭示结构，以及拉曼光谱如何对表面的组成敏感。

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.