Collaborative Research: Unusual Temperature Dependent Behavior of Polymer Nanocomposites

将纳米颗粒整合到聚合物中导致复合材料的热、机械和形状改变性能的增强。在常规聚合物复合材料中，通常采用与基质聚合物化学性质相同的聚合物官能化纳米颗粒表面，以简单地控制颗粒分散。然而，在高温加工和应用过程中保持分散和机械性能在聚合物产品的制造和性能中至关重要。该基金的重点是了解颗粒-聚合物相互作用对分散，机械性能和加工的作用。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。可逆硬化复合材料可用于各种应用，从软机器人，柔性电子产品到可注射植入物，其中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实验和分子动力学模拟方面的专业知识，以研究潜在的机制。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。为扩阔高中学生对纳米科学及纳米材料的认识，研究员计划为新泽西及纽约地区的教师举办工作坊，探讨聚合物纳米复合材料的可逆硬化现象。假设涂覆有高玻璃化转变温度（Tg）聚合物并分散在低Tg聚合物中的颗粒在加热时表现出液体到固体的转变。实验工作的目的是显示这种行为的普遍性，在不同的玻璃化转变温度差的各种混溶共混物。这一现象将应用于磁性纳米粒子，以证明机械行为可以通过粒子的局部加热来调节。此外，额外的实验，涉及局部粘度和颗粒弛豫在不对称共混物的界面，以捕捉实验系统设计中的物理和机械响应的计划。模拟将并行运行，并将用于指导材料设计，更重要的是将确定导致高温硬化的原子尺度物理学。将进行加工研究，以了解界面层的稳定性，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，其中材料在预期用于体内骨形成期间将经历频繁和受控的动态载荷。

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.