Anisotropic copoly(imide oxetane) coatings and articles of manufacture, copoly(imide oxetane)s containing pendant fluorocarbon moieties, oligomers and processes therefor
Inventors
Wohl, Christopher J. • Connell, John W. • Siochi, Emilie J. • Smith, Joseph G.
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-9822088-B2
Publication Date
2017-11-21
Expiration Date
2031-11-01
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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 that 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
Copoly(imide oxetane) materials are provided that possess the mechanical, thermal, chemical, and optical properties associated with polyimides while exhibiting a low surface energy. These copoly(imide oxetane)s are prepared using a minor amount of an amino terminated fluorinated oxetane-derived oligomer, where sufficient fluorine-containing segments migrate to the exterior surface of the polymeric material, yielding low surface energies. Preferred copolymers have surface saturation with fluoro-groups at very low content of oxetane oligomer, below about 0.5 mass percent.
The invention addresses the problem that modifying high performance polymeric materials to alter surface characteristics often degrades their desirable bulk properties, due to the need for high modifier content that disperses within the polymer interior rather than enriching the surface. Additionally, low surface energy polymers like fluorinated aliphatic polymers have limitations such as poor adhesion and processing difficulty. Polyimides have excellent bulk properties but lack low surface energy. This invention enables selective surface modification imparting low surface energy without sacrificing polyimide bulk properties.
The copoly(imide oxetane)s contain divalent radicals of fluorine-containing oxetane-derived oligomers, preferably from oxetanes with perfluorinated substituents at the beta carbon. The oxetane oligomer content in the copolymer is often less than about 10 or 15 mass percent, preferably less than about 1 mass percent, and in some embodiments between 0.001 and 0.1 mass percent. These copolymers achieve water contact angles above about 85°, preferably greater than about 90°, demonstrating surface hydrophobicity achievable with minimal oxetane content, maintaining polyimide characteristics.
Claims Coverage
The patent claims cover oligomers and copoly(imide oxetane)s incorporating those oligomers, detailing their chemical structure and functional content, and the invention's specific compositional features.
Oligomer with defined chemical structure and fluorinated oxetane segments
An oligomer represented by a formula comprising divalent aromatic hydrocarbon moieties connected via an oligomeric segment derived from fluorinated oxetane units and substituents, where the oligomer bears either nitro or amino end groups, with specified ranges for chain lengths and fluorine-containing substituents that affect surface energy.
Low content fluorinated oxetane oligomers in copoly(imide oxetane)s
Copoly(imide oxetane)s containing from 0.001 to 15 mass percent, preferably 0.001 to 0.1 mass percent, of the defined fluorinated oxetane oligomer as a reactant with amino end groups, enabling low surface energy properties with minimal modifier content.
Together, these claims focus on synthesizing oligomers with specific fluorinated oxetane structures and incorporating low amounts of these oligomers into copoly(imide oxetane)s to achieve anisotropic fluorine surface composition and low surface energy without compromising polyimide bulk properties.
Stated Advantages
Materials exhibit low surface energy with water contact angles greater than about 85°, often greater than 90°.
Low fluorinated oxetane content suffices to achieve desired surface hydrophobicity, preserving polyimide mechanical, thermal, chemical, and optical properties.
Coatings and articles exhibit an anisotropic fluorine distribution with higher fluorine concentration at the surface, improving surface characteristics.
The copoly(imide oxetane)s enhance the viability of polyimides in applications where homopolyimides have been unacceptable.
Documented Applications
Coatings on various substrates including metal, ceramic, glass, wood, paper, fibers, textiles, membranes, or polymer surfaces for imparting low adhesion and low surface energy.
Articles of manufacture made by casting, molding, or extruding copoly(imide oxetane)s exhibiting low surface energy and anisotropic fluorine surface composition.
Marine biofouling mitigation, membrane fouling resistance, insect adhesion reduction on aircraft surfaces, microbial contamination control in sterile environments, and surface particle contamination resistance.
Polymer composites that incorporate copoly(imide oxetane)s with particulate fillers to achieve water contact angles of at least 100°, advantageous for hydrophobic coatings.
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