Development and Study of Printable Stimuli-Responsive Model Polymer Systems

The study of stimuli-responsive materials that act as transducers, converting one form of energy to another, has become a significant topic of research over the past several decades. For example, some polymers functionalized with azobenzene have been shown to convert light energy to mechanical work when exposed to specific wavelengths of light. Stimuli-responsive materials may provide significant advantages in applications that require wireless actuation or autonomous adaptation to environmental stimulus. Liquid crystalline polymers are promising materials that have been shown to experience large mechanical deformations under thermal or photo stimulus. However, the fabrication of these materials has primarily only been successful in making 2D polymeric sheets. Therefore, the resulting engineering design space is limited. Our long-term goal is to explore ways in which these materials can be processed effectively using a 3D printer to create more complex 2D and 3D geometries. The first step to achieve this goal is to create a model polymer system based on liquid crystalline monomers. A key feature that these polymers must exhibit is thermoplastic behavior, so that the polymer melts at elevated temperatures which allows them to be printed. To achieve this feature, we studied two polymers systems that feature physical crosslinking. One of the systems that was studied involves the use of metallophilic interactions, which forms a silver ion backbone cross-link in the polymer network. The other system that was explored was a polyimidothioether. These polymers incorporate soft flexible segments that are linked through hard rigid segments that form physical aggregates. Herein, we will summarize the synthesis and some preliminary characterization of these materials. By establishing a robust printable liquid crystalline polymer, the potential exists to design systems that respond to environmental stimuli such as light or heat, making this material attractive for the aerospace, biomedical, and textile industries.