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Completed TRL 1 (started at 1, targeting 3)
There is currently a very limited set of engineering polymers that have been demonstrated as viable for use in 3-D printing. Additive manufacturing of custom components will require a much larger array of polymers, especially those with physical, thermal, chemical, and mechanical properties that can be tailor-made. The development of ‘Ionic Polyimides’ offers a solution to this shortage by combining the well understood and widely accepted properties of conventional polyimides, with a new approach to polymer synthesis. Polyimides and polymeric ionic liquids (poly(ILs)) are at the forefront of advanced polymer materials, each with their own set of advantages and disadvantages. While it is clear that more types of polymer materials are needed for fused deposition modeling (FDM) additive manufacturing, there is a need to explore these classes of materials. The synthesis process developed by the Bara Research Group at the University of Alabama allows full control over polymer structure, nanostructure, thermal, electrical, and physical properties making them a prime candidate for use in the additive manufacturing process. Furthermore, the new process allows us to tailor-make a high strength polymer that can be used to fabricate filament feedstock instead of pellets for 3D printing.
As a continuation of our previous work, we are venturing into modeling the polymer “building blocks” to more rapidly identify viable ionic polyimide configurations (i.e. polyimides with the correct thermal, chemical, and physical properties for 3D printing). We plan to use data collected in the first year CIF to anchor the model we are developing in this proposal to correlate synthesis and thermal characterization of this polyimides. Resources for this effort will be used to collaborate with the Co-PI Professor Jason Bara from the University of Alabama (UA), and Kendall Byler a Computational Chemist from the University of Alabama-Huntsville. Jason Bara, and the Bara Research Group, will continue to synthesize ionic polyimides, and Kendall Byler will continue to conduct molecular dynamic simulations of each of the polyimide structures. This proposal requests 0.50 FTE and $50K in procurements from the Center Innovation Fund (CIF) which is a continuation from FY17 CIF. Deliverables are a set of structure-property relationships (e.g. Tg/Tm relative to different ionic polyimide structures). This will provide a further understanding of the first generation of materials produced from this process which can then be used for proof-of-concept in additive manufacturing as well as to guide to the development of further materials.
Accomplishments from Year 1:
Presently, we have received and characterized eight ionic polyimides synthesized by the Bara Research Group. To date, we have conducted a differential scanning calorimetry (DSC) analysis and a Fourier transform infrared-spectroscopy (FT-IR) analysis on all eight building blocks to determine the thermal properties of each sample, and the relative abundance of the elements/molecules in each sample. Also, we have modeled eight of the building blocks using the Gaussian 16 and Spartan 16 simulation packages.
The primary objective of this proposal is to determine the relationship between molecular structure, physical properties, and performance of ionic polyimides. Further, we seek to determine their utility as materials suitable for additive manufacturing of components used in aerospace vehicles, with an emphasis on characterizing and simulating their thermal behaviors and properties. This proposal addresses the need for fundamental research on a customizable polymer filament feedstock for 3-D printing with tailor-made properties potentially making it superior to the commercial blends offered in industry today. The deliverables for this project are the creation of a database that will detail the relationships between the molecular structure and physical properties for the ionic polyimide of interest (e.g. Tg/Tm relative to different ionic polyimide structures). This new database will provide a “road map” to the development of the first generation of materials and ultimately proof-of-concept.
The proposal is a continuation and aligns with the “Advanced Manufacturing” FY17/18 Focus Domain. This research will focus on additive manufacturing to develop in-space manufacturing capabilities for space exploration. The innovation is revolutionary because unlike any material currently available for 3-D printing, ionic polyimides retain the robust nature of polyimides while displaying the ease of processing and conductivity of poly(ILs). This unique combination of properties is not found in conventional polyimides or other engineering polymers. The use of these materials will allow for potential aerospace applications such as valves, O-rings, seals and gears. Bara’s group has already demonstrated that their first-generation ionic polyimides can be extruded, pelletized and molded at ~220oC, which is consistent with modern 3-D printers. Thus, it is imperative to rapidly begin to elucidate the thermal behaviors of these materials to gain an understanding of the key structural variables that must be manipulated to develop further generations of application-specific materials. The benefits associated with poly(ILs) are the following:
The synthesis process is carried out in a “one pot” approach with excellent yield and purity. Each of the requisite starting materials can be easily changed. This is how we will “tailor-make” the molecular structure of the ionic polyimide to yield the thermal, mechanical, and physical properties we want. Figure 2 shows thin films of ionic polyimides that the Bara Research Group has fabricated through melt casting. This project will focus on key subsets of distinct structural variables to efficiently characterize the influence of structure on thermal properties.
The “building blocks,” as well as other commercially available starting materials, yield 10,000’s if not 100,000’s of feasible ionic polyimide compositions. The state of the art additive manufacturing process is limited to widely known engineering polymers such as PEEK/PEKK and Ultem. While Ultem can be used in the FDM process, PEEK/PEKK can only be used in laser sintering printers. Most other polymers for 3-D printing have inferior properties. The most viable structures in this project will be those which are believed to be most economic for initial scale up. Specifically, we will focus on the use of the PMDA and API molecules in combination with various linker molecules such as para-dichloroxylene and meta-dichloroxylene. The Tf2N anion will also be the primary anion of interest due to its robust thermal and chemical stability. We will also dope the ionic polyimides with “free” ILs to understand the effects of an added plasticizer. This holds great promise for developing multiple material platforms to meet the demands of manufacturing lightweight components with unique thermal/conductivity/physical properties for use in aerospace applications such as valves, O-rings, seals, and gears.
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