INTELLECTUAL MERIT: Shape memory polymers (SMPs) are proving to be an attractive, novel tool in biomedical applications including self-tightening sutures, self-deploying stents, and drug delivery vehicles. The transition in dual SMPs is characterized by a change from shape A to shape B upon direct or indirect triggering typically by heat and more recently by light. Triple shape polymeric materials (TSPs), first developed in 2006, have received increased attention in biomedical research due to their ability to perform complex movements (for example, shape A to B to C). In spite of the unique mobility properties of both systems, there remain significant challenges. Specifically, for dual shape memory polymers in many of the proposed biomaterials applications, the transition temperature (T-trans) should be near body temperature (37 °C). However, because the T-trans is altered by several factors (molecular weight, crosslink density, functionality), it is often challenging to target specific transition temperatures, as any change in either property results in a T-trans shift. Triple shape materials often take advantage of multiphase polymer networks with two phase-separated domains, and therefore two independent transition temperatures. As a result, the transition temperature and property control challenges seen in dual shape memory are even more pronounced in the triple shape system. To address these issues, novel polymeric biomaterials that possess two independent transitions (photo and thermal) within a single temperature range will be designed. For the polymers that possess transitions between room and body temperature, the thermal shape memory properties will be characterized and combined with light-induced shape memory to form unique triple shape materials. Finally, using a modified PRINT (Pattern Replication in Non-Wetting Templates) fabrication method, multi-functional shape memory polymers with the ability to shape shift on the macro and micro/nano scales will be created. To our knowledge, there are no examples of polymeric biomaterials that possess independent thermal and photo switches that can be combined for triple shape memory. At the end of three years these materials will have been developed, their unique properties elucidated and insight gained into their potential as unique multifunctional biomaterials. Potential fields of application include those that require materials capable of complex movement, such as minimally invasive surgery, where multifunctional stents, catheters, and valves could prove to be significant advances in the next generation of smart medical devices.
BROADER IMPACTS: The understanding of shape memory biomaterials will be advanced, while teaching and training will be promoted . Graduate students will learn how to solve problems by starting with polymer design and synthesis and continuing through materials characterization and applications. Undergraduates and high school student researchers will be presented with intriguing, relevant problems that can be answered in the laboratory using organic synthesis, analytical chemistry, and biological techniques. The interdisciplinary interaction will also be an educational opportunity for all students, as they will be active participants in the collaborative research. Additionally, it is expected that the research results will be incorporated, where appropriate, into the teaching of undergraduate organic chemistry and graduate polymer science to help students appreciate the utility of basic concepts. All students will be encouraged to present their research at conferences and publish their research in the appropriate journals. The PI will mentor underrepresented high school, undergraduate and graduate students, as well as junior faculty in various workshops, presentations and research experiences. Finally, the PI will utilize her role as UNC NSF AGEP Director to continue the mentoring of undergraduates interested in pursuing doctoral degrees in STEM fields and graduate students in doctoral programs in STEM fields who are interested in research and teaching careers.
