Frost-resistant and Antifogging Polymeric Composite Films Capable of Healing Fractured Nanofibers

Micro- and/or nanoscaled structures have endowed artificial polymeric materials with various unique functions. However, these materials are vulnerable to mechanical damage, which can destroy their inherent micro- and/or nanoscaled structures and result in the loss of their original functions. Therefore, to extend the service life of artificial polymeric materials whose functions depend on micro/nanostructures, it is highly important to fabricate polymeric materials that can heal damaged micro/nanoscaled structures. In this work, we report the fabrication of self-healing antifogging and frost-resisting films capable of healing the fractured nanofibrils. The films are fabricated by dip-coating of clean substrate from aqueous solution of poly(acrylic acid)-block-poly(acrylamide) (PAA-b-PAAm) and poly(diallyldimethylammonium chloride) (PDDA) complexes, followed by annealing under a humid environment of similar to 25 degrees C and relative humidity of similar to 100% (denoted as PAA-b-PAAm/PDDA). The complexation of PAA-b-PAAm and PDDA in aqueous solutions can assemble into nanorods, which are comprised of electrostatically cross-linked PAA blocks and PDDA chains as the hydrophobic cores and hydrogen-bonded PAAm chains as the hydrophilic coronas. These nanorods in the complex solutions can fuse into oriented nanofibers in the dip-coated PAA-b-PAAm/PDDA films during the dip-coating and the annealing processes. Nanofibrillar structures of the hydrophilic PAA-b-PAAm/PDDA film can increase the contact area between water droplets and film surfaces to facilitate water dispersion and adsorption, thereby endowing the film with excellent antifogging and frost-resisting properties. Because of the dynamic nature of electrostatic and hydrogen-bonding interactions, the PAA-b-PAAm/PDDA films can not only heal physical cuts with several tens of micrometer width, but also reconnect the fractured nanofibers to restore their original ordered nanostructures. The ability to heal macroscopic damages and restore inherent nanostructures can largely extend the service life and enhance the reliability of the antifogging and frost-resisting PAA-b-PAAm/PDDA films. The present work paves a way for the fabrication of polymeric materials that can heal micro/nanostructures and thus restore their original functions. [GRAPHICS] .