Shape Memory Elastomers Derived from Ionomer/Fatty Acid Blends

University Of Akron, Akron OH

Investigators

Abstract

TECHNICAL SUMMARY Shape 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 SUMMARY Shape 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.