Shape Memory Elastomers Derived from Ionomer/Fatty Acid Blends

形状记忆聚合物（SMP）是一种在外界刺激下具有改变形状能力的材料。最常见的形状记忆材料类型是通过温度变化来实现形状变化的材料，即热诱导形状记忆效应。这种材料具有至少两个独立的交联网络，其中至少一个是热可逆的。材料通常由于共价交联网络而具有永久形状，但它们可以在第二种可逆网络的热转变（Tc）以上重塑，并在应力下冷却到低于Tc时固定为临时形状。当再加热到临界温度以上时，由于熵弹性，材料记忆并恢复到永久形状。这项工作的目的是开发和了解基于弹性体离聚体和低摩尔质量脂肪酸或其盐类混合物的新型SMP的结构和性能。一个主要的目标是了解这些材料中形状记忆的分子起源。纳米分离的离聚体或共价交联的离聚体将用于开发永久网络。聚合物和脂肪酸（盐）之间非常强的离子或偶极相互作用将使脂肪酸（盐）的晶体具有热可逆的物理交联功能，可以提供暂时的形状。由于脂肪酸（盐）的熔点为Tc，因此通过为化合物选择合适的脂肪酸（盐）可以很容易地控制形状记忆效应的温度。这将为Tc的定制提供显著的多功能性，以及SMP的机械性能。形状记忆聚合物（SMP）应用于医疗设备（正畸金属丝、具有药物输送能力的聚合物支架、可生物降解植入物、智能手术缝合线）、执行器、传感器、人造肌肉、开关、智能纺织品和自展开结构。该项目将开发一种新型的多功能SMP，并培训科学家在智能材料领域工作，这是许多高科技应用的使能技术。该基金专门支持两名研究生和化学工程本科学生的工作，他们将通过独立学习或作为REU学生参与该项目。PI和学生还将参与旨在提高K-12学生和教师对科学技术，特别是智能材料领域的接触的教育和推广计划。其中包括大学？“达芬奇计划”（DaVinci Project）帮助数学和科学教师（7-12年级）将工程融入课堂；“伽利略计划”（Galileo Project）向高中生和K-12教育工作者介绍核心工程概念和解决问题的实践。此外，国家科学基金会资助的路易斯·斯托克斯少数民族参与联盟（LSAMP）将用于介绍少数民族学生进行研究。研究结果将发表在著名的同行评议期刊上，并在国际科学大会上发表。

TECHNICAL SUMMARYShape memory polymers (SMP) are materials that have the capability of changing shape when exposed to some external stimulus. The most common type of shape memory material is one for which the shape change is achieved by changes in temperature, i.e., a thermally-induced shape memory effect. Such materials possess at least two independent crosslinked networks, at least one of which is thermally reversible. The materials have a permanent shape due usually to a covalently crosslinked network, but they can be reshaped above a thermal transition (Tc) of a second, reversible network and fixed into a temporary shape when cooled under stress to below Tc. When reheated above the critical temperature, the material remembers and reverts to the permanent shape due to entropy elasticity. The objective of the proposed work is to develop and understand the structure and properties of a new class of SMP based on blends of an elastomeric ionomer and low molar mass fatty acids or their salts. A major goal is to understand the molecular origin of shape memory in such materials. Nanophase separation of the ionomer or covalent crosslinking of the ionomer will be used to develop the permanent network. Very strong ionic or dipolar interactions between the polymer and the fatty acid (salt) will allow crystals of the fatty acid (salt) to function as thermally reversible, physical crosslinks that can provide a temporary shape. Since, the melting point of the fatty acid (salt) serves as Tc, the temperature of the shape memory effect can be easily controlled by choosing an appropriate fatty acid (salt) for the compound. This will provide significant versatility in the tailoring of Tc, as well as the mechanical properties of the SMP. NON-TECHNICAL SUMMARYShape memory polymers (SMP) have applications as medical devices (orthodontic wires, polymer stents with drug delivery capabilities, biodegradable implants, smart surgical sutures), actuators, sensors, artificial muscles, switches, smart textiles and self-deployable structures. This project will develop a new, versatile type of SMP and train scientists to work in the field of smart materials, which is an enabling technology in many high-tech applications. The grant specifically supports the work of two graduate students and undergraduate chemical engineering students will participate in the project through independent study or as REU students. The PI and students will also participate in education and outreach programs designed to enhance exposure of K-12 students and teachers to science and technology, specifically in the field of smart materials. These include the University?s residential Engineering 2000 program that targets minority students, the DaVinci Project that helps math and science teachers (grades 7-12) to integrate engineering into the classroom, and the NSF-funded Galileo Project that introduces high school students and K-12 educators to core engineering concepts and problem-solving practices. In addition, the NSF-funded Louis Stokes Alliance for Minority Participation' (LSAMP) will be used to introduce minority students to research. The results of the research will be published in prestigious, peer-reviewed journals and presented at international scientific congresses.