Copoly(alkyl ether imide)s were synthesized for the purposes of tailoring surface chemistry. Alkyl ether oligomers with amine end groups were synthesized from the hydroxyl-terminated species, and subsequently reacted with aromatic dianhydrides and diamines to make the copolymers. Films were solution-cast from the copolymers and exhibited reduced surface energy and increased surface fluorine content at extremely low loadings relative to the imide matrix. These copolymers are currently being evaluated for mitigation of particle adhesion and fouling from exposure to various particle and biological contaminants. Additionally, the surface migration of the oxetane segments can be used as a shuttle to bring other designed chemical constituents to the surface.
The end-groups of alkyl ether oligomeric species were chemically modified via reaction with 4-nitrobenzoyl chloride generating nitro-terminated oligomers. The nitro groups were reduced using a catalyst (5% Pd/C) in a hydrogen atmosphere to generate amino-terminated oligomers. These materials were characterized using both proton and carbon nuclear magnetic resonance (NMR) spectroscopy. NMR was used to characterize the chemical composition and to determine the molecular weight of the end-group functionalized oxetane oligomers.
The amine-terminated alkyl ether oligomers were copolymerized with diamines and dianhydrides to generate the copoly(alkyl ether imide)s. This condensation polymerization reaction was performed by first dissolving the alkyl ether oligomers in dimethyl acetamide (DMAc). Next, the diamines-functionalized monomer was added to a threenecked, round-bottomed flask outfitted with a mechanical stirrer and a nitrogen inlet. DMAc was added to the flask, followed by the alkyl ether solution. The contents of the flask were stirred for 10 minutes, after which the dianhydride functionalized monomer was added, and the solution was stirred under nitrogen overnight. The weight percentage of the alkyl ether component was varied from 0.01 to 10 wt %. The following day, a sample of the polyamide acid solution was made for determination of inherent viscosity (a method to qualitatively evaluate the polymer molecular weight), and another portion was placed in a centrifuge tube and spun to remove air bubbles for film casting. A film was cast from the polyamide acid solution using a doctor blade. The cast film was placed in a forced-air chamber to remove the solvent until the film was tack-free. The dried film was then placed in a nitrogen oven to thermally imidize at a maximal temperature of 250 °C. Samples of the polyamide acid solution were also chemically imidized via reaction with the pyridine and acetic anhydride.
The resultant copoly(alkyl ether) films were characterized using surface-sensitive techniques including x-ray photoelectron spectroscopy (XPS), water contact angle goniometry, and attenuated total reflection infrared (ATR-IR) spectroscopy. The mechanical properties of the film were also determined using tensile testing.
This work was done by Christopher Wohl and John Connell of Langley Research Center. LAR-18026-1