Anisotropic copoly(imide oxetane) coatings and articles of manufacture, copoly(imide oxetane)s containing pendant fluorocarbon moieties, oligomers and processes therefor
Inventors
Wohl, JR., Christopher J. • Connell, John W. • Siochi, Emilie J. • Smith, Jr., Joseph G.
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-11130742-B2
Publication Date
2021-09-28
Expiration Date
2031-11-01
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Abstract
Copoly(imide oxetane) materials are disclosed that can exhibit a low surface energy while possessing the mechanical, thermal, chemical and optical properties associated with polyimides. The copoly(imide oxetane)s are prepared using a minor amount of fluorinated oxetane-derived oligomer with sufficient fluorine-containing segments of the copoly(imide oxetane)s migrate to the exterior surface of the polymeric material to yield low surface energies. Thus the coatings and articles of manufacture made with the copoly(imide oxetane)s of this invention are characterized as having an anisotropic fluorine composition. The low surface energies can be achieved with very low content of fluorinated oxetane-derived oligomer. The copolymers of this invention can enhance the viability of polyimides for many applications and may be acceptable where homopolyimide materials have been unacceptable.
Core Innovation
This invention provides copoly(imide oxetane) materials that combine the low surface energy properties of fluorinated polymers with the mechanical, thermal, chemical, and optical properties characteristic of polyimides. It achieves this by incorporating a minor amount of amino terminated fluorinated oxetane-derived oligomer into the polyimide matrix, whereby sufficient fluorine-containing segments migrate preferentially to the polymer's exterior surface, producing low surface energy and an anisotropic fluorine composition. The coatings and articles manufactured from these copoly(imide oxetane)s have surfaces saturated with fluoro-groups even at very low oligomer content, below about 0.5 mass percent, enabling tailored surface properties without compromising bulk characteristics.
The problem addressed stems from the challenge of modifying high-performance polymers to introduce low adhesion or low surface energy properties without degrading their mechanical, thermal, and optical properties. Conventional approaches, such as using fluorinated homopolymers or surface modifying agents, either produce materials with poor adhesion, processing difficulties, or require high modifier content that reduces desirable bulk properties. Additionally, modifiers often remain dispersed inside the polymer and do not contribute effectively to surface characteristics. There is a need for polyimide-based materials that possess low surface energy surfaces but retain polyimide's superior bulk properties.
This invention overcomes these limitations by employing fluorine-containing oxetane oligomers as minor components in copoly(imide oxetane)s, enabling the fluorine groups to migrate to and concentrate at the surface. This results in coatings and articles with anisotropic fluorine distribution, where the surface exhibits hydrohobicity with water contact angles often greater than 85°, preferably above 90°, at very low dopant levels. The copolymers maintain desirable mechanical and thermal properties since the fluorinated oligomer content is kept minimal. The invention also discloses methods for preparing these materials using diamine-terminated fluorinated oxetane oligomers, polyamic acid intermediates, and imidization to form the final copoly(imide oxetane) products.
Claims Coverage
The patent contains several independent claims covering the copoly(imide oxetane) structures, related coatings, polymers with fillers, articles of manufacture, and methods for making these materials.
Copoly(imide oxetane) structure with fluorinated oxetane segments
The copoly(imide oxetane) polymer is defined by having a repeating unit -(G-M)-(D-M)- where G contains a fluorinated oxetane-derived segment J, M contains hydrocarbyl moieties with optional heteroatoms, and D is a diamine-derived segment also containing hydrocarbyl moieties. J can be a block or random oligomer of fluorinated oxetane monomers with specified substituents. Parameters such as chain length (m, p, q, r), fluorination pattern, and oligomer composition are defined precisely.
Coatings with anisotropic fluorine distribution
Coatings comprising the copoly(imide oxetane) have an anisotropic distribution of fluorine atoms, with a higher concentration at the outer surface, and achieve a water contact angle of at least 90°.
Method for coating a substrate with copoly(amic acid oxetane) followed by imidization
Applying a solution containing copoly(amic acid oxetane) precursor, which includes the fluorinated oxetane segment, onto a substrate and subjecting the coated substrate to imidization conditions to form the copoly(imide oxetane) coating with desired surface properties.
Polymer composite with particulate filler enhancing water contact angle
A polymer composite containing the copoly(imide oxetane) and particulate fillers that exhibits a water contact angle of at least 100°.
Articles of manufacture with fluorine-enriched outer surfaces
Polymeric articles containing the copoly(imide oxetane) that have higher concentrations of fluorine atoms at their outer surface than in the polymer matrix, achievable by casting, molding, or extrusion.
Methods for making articles with fluorine-rich surfaces
Forming a polymeric matrix containing copoly(amic acid oxetane), shaping it, and imidizing it, optionally coating the surface with the diamine oligomer or copoly(amic acid oxetane) before imidization to achieve fluorine concentration at the outer surface.
The independent claims collectively cover the synthesized copoly(imide oxetane) polymers with fluorinated oxetane segments, the manufacture and use of coatings and composites containing these materials exhibiting anisotropic fluorine distribution and low surface energy, articles offering fluorine-enriched surfaces, and methods for preparing these materials and articles by polymerization and processing techniques.
Stated Advantages
Low surface energy coatings and articles are achieved with very low content of expensive fluorinated oxetane oligomer, minimizing impact on bulk properties.
The copoly(imide oxetane)s maintain the mechanical, thermal, chemical, and optical properties associated with polyimides while improving surface hydrophobicity.
Anisotropic fluorine distribution allows surface fluorine saturation, enhancing resistance to fouling, contamination, and adhesion without compromising material integrity.
The copolymers enhance viability of polyimides in applications where homopolyimide materials were previously unacceptable.
Documented Applications
Coatings with low adhesion surfaces suitable for reducing marine biofouling, membrane fouling, insect adhesion on aircraft surfaces, microbial contamination, and particulate contamination.
Protective coatings for spacecraft surfaces (e.g., lunar dust mitigation) in environments where active mitigation is impractical.
Insulating films and coatings in the electronic industry requiring mechanical strength and thermal stability combined with low surface energy.
Articles of manufacture including fibers, bushings, bearings in jet engines, and other demanding structural parts where low surface energy and durability are desired.
Interested in licensing this patent?