Collaborative Research: Unusual Temperature Dependent Behavior of Polymer Nanocomposites

将纳米颗粒整合到聚合物中可以增强复合材料的热、机械和形状变化性能。功能化纳米颗粒表面的聚合物在化学上与基体聚合物相同，通常用于传统的聚合物复合材料中，只是为了控制颗粒的分散。然而，在高温加工和应用过程中保持分散和机械性能对聚合物产品的制造和性能至关重要。这项资助的重点是了解颗粒-聚合物相互作用在分散、机械性能和加工中的作用。为了实现这一目标，pi将专注于材料系统设计，并对可逆机械响应进行按需控制。可逆增强复合材料可用于各种应用，从软机器人，柔性电子到可注射植入物，在加热时应保持机械完整性。这项合作工作提供了一个基础研究计划，整合了pi在聚合物纳米复合材料的实验和分子动力学模拟方面的专业知识，以研究其潜在机制。此外，该项目还为研究生和本科生提供纳米材料设计和加工方面的教育。为了在高中教育中扩大纳米科学和纳米材料的知识，pi的目标是为新泽西和纽约地区的教师组织一个研讨会。该团队旨在探索聚合物纳米复合材料中的可逆硬化现象。假设粒子包被高玻璃化转变温度（Tg）聚合物并分散在低Tg聚合物中，加热后表现出液固转变。实验工作旨在证明这种行为在不同玻璃化转变温差的各种混相共混物中的普遍性。这一现象将被应用于磁性纳米颗粒，以证明机械行为可以通过局部加热颗粒来调节。此外，为了在实验系统设计中捕捉到物理和机械响应，还计划了更多的实验来联系非对称共混物在界面上的局部粘度和粒子弛豫。模拟将并行运行，并将用于指导材料设计，更重要的是将识别导致高温下硬化的原子尺度物理。将进行加工研究，以了解间相层的稳定性，以及加工后的复合材料结构（形态）和性能。处理结果与材料设计非常相关，例如生物医学植入物，其中材料在体内骨形成的预期使用期间将经历频繁和受控的动态负载。

Integration of nanoparticles into polymers leads to enhancement in thermal, mechanical and shape changing properties of composite materials. Functionalizing nanoparticle surfaces with polymers that are chemically identical to matrix polymer are commonly employed in conventional polymer composites simply to control particle dispersion. However, maintaining dispersion and mechanical properties during high temperature processing and applications holds a critical importance in manufacturing and performance of polymeric products. This grant focuses on understanding the role of particle-polymer interactions on dispersion, mechanical properties and processing. Towards this goal, the PIs will focus on a material system design with on-demand control on reversible mechanical response. Reversibly stiffening composites can be used in various applications from soft robotics, flexible electronics to injectable implants where mechanical integrity should be maintained when heated. This collaborative work offers a fundamental research plan integrating the expertise of the PIs on experimental and molecular dynamics simulations on polymer nanocomposites to study the underlying mechanisms. In addition, the project offers to educate graduate and undergraduate students on nanomaterials design and processing. To broaden the knowledge of nanoscience and nanomaterials in high school education, the PIs aim to organize a workshop for teachers in New Jersey and New York area.The team aims to explore the phenomenon of reversible stiffening in polymer nanocomposites. It is hypothesized that particles coated with a high glass transition temperature (Tg) polymer and dispersed in a low-Tg polymer exhibit liquid-to-solid transition upon heating. Experimental work is designed to show the universality of this behavior in various miscible blends with different glass-transition temperature differences. The phenomenon will be employed on magnetic nanoparticles to demonstrate that the mechanical behavior can be regulated with local heating of particles. Moreover, additional experiments to relate the local viscosity and particle relaxations in asymmetric blends on interphases are planned in order to capture the physics and mechanical response in the experimental system design. Simulations will run in parallel and will be used to guide the material design and more importantly will identify the atomistic scale physics that leads to stiffening at high temperatures. Processing studies will be conducted to understand the stability of interphase layers, and composite structure (morphology) and properties after processing. The processing results are very relevant for the material design such as for biomedical implants where materials will experience frequent and controlled dynamic loadings during their intended use for in vivo bone formation.