Shape Memory Elastomers Derived from Ionomer/Fatty Acid Blends

技术概述形状记忆聚合物（SMP）是当暴露于一些外部刺激时具有改变形状的能力的材料。最常见类型的形状记忆材料是通过温度变化实现形状变化的材料，即，热致形状记忆效应。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。这些材料通常由于共价交联的网络而具有永久形状，但它们可以在高于第二可逆网络的热转变（Tc）时再成形，并且当在应力下冷却至低于Tc时固定成临时形状。 当重新加热到临界温度以上时，材料会记住并恢复到永久形状，这是由于熵弹性。所提出的工作的目的是开发和理解的结构和性能的一类新的SMP的基础上的弹性体离聚物和低摩尔质量的脂肪酸或其盐的共混物。一个主要的目标是了解这种材料中形状记忆的分子起源。离聚物的纳米相分离或离聚物的共价交联将用于形成永久网络。聚合物和脂肪酸（盐）之间非常强的离子或偶极相互作用将允许脂肪酸（盐）的晶体用作可提供临时形状的热可逆物理交联。由于脂肪酸（盐）的熔点用作Tc，因此通过选择合适的脂肪酸（盐）用于化合物，可以容易地控制形状记忆效应的温度。这将在Tc的定制以及SMP的机械性能方面提供显著的多功能性。非技术概述形状记忆聚合物（SMP）可用作医疗器械（正畸线、具有药物递送能力的聚合物支架、可生物降解的植入物、智能外科缝合线）、致动器、传感器、人造肌肉、开关、智能纺织品和可自展开的结构。该项目将开发一种新的多功能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一项使能技术。 该补助金特别支持两名研究生和本科化学工程学生的工作将通过独立学习或作为REU学生参与该项目。 PI和学生还将参加旨在提高K-12学生和教师对科学和技术的接触的教育和推广计划，特别是在智能材料领域。其中包括大学？美国国家科学基金会资助的住宅工程2000计划，针对少数民族学生，达芬奇项目，帮助数学和科学教师（7-12年级）将工程融入课堂，以及伽利略项目，介绍高中学生和K-12教育工作者的核心工程概念和解决问题的做法。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）将用于向少数民族学生介绍研究。 研究结果将发表在著名的同行评审期刊上，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.