High Temperature Shape Memory Polymers

技术摘要：NSF资助的研究目标是开发和了解基于离聚体和低分子晶体化合物(LMWC)混合物的高温形状记忆聚合物(HTSMPS)的结构和性能。这包括对形状记忆在这些双组分系统中的分子起源有一个基本的理解。这些材料中的永久交联物是基于离聚体或共价交联物中离子纳米结构域的微相分离，并将评估每种设计的优缺点。该临时网络来源于离聚体与LMWC分散相之间较强的分子间相互作用，其转变温度T_c由LMWC的熔点控制。实验工作包括熔融复合法制备HTSMPS，并对其形貌、物理性能和力学性能进行了表征。形状记忆特性将通过动态力学分析测量的形状记忆循环来评估，形状可逆性的可持续性将通过使用更大原型样本的循环测试实验来评估。最初的研究重点将是部分磺化的聚醚醚酮和油酸钠的混合物，目标温度为~200°C，但其他基于聚砜和聚酰亚胺衍生的高温离聚体矩阵的体系以及其他低分子量碳材料，如脂肪酸、低熔点混合物、离子液体、高熔点有机化合物、锡合金和磷酸盐玻璃，将被考虑评估离聚体/低分子量碳化钨形状记忆聚合物设计的有效性。非技术概述：形状记忆聚合物(SMP)是一种能够在外部刺激(如温度、光或电场或磁场)作用下改变形状的材料。这些智能材料的应用包括正畸钢丝、聚合物支架、可生物降解植入物、人造肌肉、执行器、传感器、开关和智能纺织品。大多数开关磁阻材料是软的热激活材料，其形状转换温度低于100°C。更高温度的应用，例如具有高强度和刚性的可扩展结构(例如，可展开的太阳能电池板、天线和反射器)以及形状变形表面和结构(例如，飞机机翼)，需要更高的工作和转换温度。该NSF奖支持开发高温形状记忆聚合物的研究，该聚合物由含有键合离子基团的热塑性聚合物和与离子聚合物强相互作用的低分子量添加剂的混合物制成。除了开发用于高性能应用的新材料，如航空航天部件，该项目还将包括培训科学家在新兴的智能材料领域工作。这项研究将涉及研究生、本科生和高中生以及高中理科教师。将特别努力从代表不足的STEM小组中招募学生参与研究。将寻求与私营行业和国家实验室的合作，以开发关于主题材料的新的基本知识，并推动新的商业应用的开发。这项研究的科学成果将通过在主要科学期刊上的快速出版物以及国际科学协会和学生在国家科学会议上的发言来广泛传播。

TECHNICAL SUMMARY: The objectives of the NSF-funded research are to develop and understand the structure and properties of high temperature shape memory polymers (HTSMPs) based on mixtures of an ionomer and a low molecular weight crystalline compound (LMWC). This includes developing a fundamental understanding of the molecular origin of shape memory in these two-component systems. The permanent crosslink in these materials is based on microphase separation of ionic nanodomains in the ionomer or covalent crosslinks, and the advantages/disadvantages of each design will be assessed. The temporary network derives from strong intermolecular interactions between the ionomer and the LMWC dispersed phase, and the switching temperature, Tc, is controlled by the melting point of the LMWC. The experimental work includes preparing HTSMPs by melt compounding and the characterization of their morphology, physical properties and mechanical properties. Shape memory characteristics will be assessed by shape memory cycles measured by dynamic mechanical analysis and the sustainability of the shape reversibility will be evaluated from cyclic testing experiments using larger prototype samples. The initial focus of the research will be mixtures of partially sulfonated poly(ether ether ketone) and sodium oleate with a targeted Tc ~ 200°C, but other systems based on high temperature ionomer matrices derived from polysulfones and polyimides and other LMWCs such as fatty acids, eutectic mixtures, fusible metals, ionic liquids, high melting point organic compounds, tin alloys and phosphate glasses will be considered to assess the efficacy of the ionomer/LMWC shape memory polymer design. NON-TECHNICAL SUMMARY: Shape memory polymers (SMP) are materials that have the capability of changing shape when exposed to an external stimulus (e.g., temperature, light or electrical or magnetic fields). Applications of these smart materials include orthodontic wires, polymer stents, biodegradable implants, artificial muscles, actuators, sensors, switches and smart textiles. Most SMPs are soft, thermally-activated materials with shape-switching temperatures lower than 100°C. Higher temperature applications, such as expandable structures with high strength and stiffness (e.g., deployable solar arrays, antennas and reflectors) and shape morphing surfaces and structures (e.g., airplane wings) require higher operating and switching temperatures. This NSF award supports research on the development of high temperature shape memory polymers made from mixtures of a thermoplastic polymer containing bonded ionic groups and a low molecular weight additive that interacts strongly with the ionic polymer. In addition to the development of new materials for high-performance applications, such as aerospace components, this project will include training scientists to work in the emerging field of smart materials. The research will involve graduate, undergraduate and high school students and high school science teachers. Special efforts will be made to recruit students form under-represented STEM groups to participate in the research. Collaborations will be sought with private industry and national laboratories to develop new fundamental knowledge of the subject materials and advance the development of new commercial applications. The scientific results from the research will be broadly disseminated through rapid publications in major scientific journals and presentations by the PI and students at national scientific meetings.