RESUMEN
Original perfluoropolyether (PFPE)-based oligomeric polyurethanes (FOPUs) with different macromolecular architecture were synthesized (in one step) as low-surface-energy materials. It is demonstrated that the oligomers, especially the ones terminated with CF3 moieties, can be employed as safer replacements to long-chain perfluoroalkyl substances/additives. The FOPU macromolecules, when added to an engineering thermoplastic (polyethylene terephthalate, PET) film, readily migrate to the film surface and bring significant water and oil repellency to the thermoplastic boundary. The best performing FOPU/PET films have reached the level of oil wettability and surface energy significantly lower than that of polytetrafluoroethylene, a fully perfluorinated polymer. Specifically, the highest level of the repellency is observed with an oligomeric additive, which was made using aromatic diisocyanate as a comonomer and has CF3 end-group. This semicrystalline oligomer has a glass transition temperature (Tg) well above room temperature, and we associate the superiority of the material in achieving low water and oil wettability with its ability to effectively retain CF3 and CF2 moieties in contact with the test wetting liquids.
RESUMEN
We fabricated thermoplastic surfaces possessing extremely limited water and oil wettability without employment of long-chain perfluoroalkyl (LCPFA) substances. Namely, by taking advantage of the structure and behavior of original oleophobic perfluoropolyether (PFPE) methacrylate (PFM) molecular bottlebrush (MBB) additive we obtained polymeric surfaces with oil contact angles well above 80° and surface energy on the level of 10 mN/m. Those angles and surface energies are the highest and the lowest respective values reported to date for any bulk solid flat organic surface not containing LCPFA. We show experimentally and computationally that this remarkable oil repellency is attributed to migration of small quantities of the oleophobic MBB additives to the surface of the thermoplastics. Severe mismatch in the affinity between the densely grafted long side chains of MBB and a host matrix promotes stretching and densification of mobile side chains delivering the lowest surface energy functionalities (CF3) to the materials' boundary. Our studies demonstrate that PFM can be utilized as an effective low surface energy additive to conventional thermoplastic polymers, such as poly(methyl methacrylate) and Nylon-6. We show that films containing PFM achieve the level of oil repellency significantly higher than that of polytetrafluoroethylene (PTFE), a fully perfluorinated thermoplastic. The surface energy of the films is also significantly lower than that of PTFE, even at low concentrations of PFM additives.
