Functionalization of fibers using azlactone-containing polymers: layer-by-layer fabrication of reactive thin films on the surfaces of hair and cellulose-based materials.

We report an approach to the functionalization of fibers and fiber-based materials that is based on the deposition of reactive azlactone-functionalized polymers and the "reactive" layer-by-layer assembly of azlactone-containing thin films. We demonstrate (i) that the azlactone-functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) can be used to modify the surfaces of a model protein-based fiber (horsehair) and cellulose-based materials (e.g., cotton and paper), and (ii) that fibers functionalized in this manner can be used to support the fabrication of covalently cross-linked and reactive polymer multilayers assembled using PVDMA and poly(ethyleneimine) (PEI). The growth, chemical reactivity, and uniformity of films deposited on these substrates were characterized using fluorescence microscopy, confocal microscopy, and scanning electron microscopy (SEM). In addition to the direct functionalization of fibers, we demonstrate that the residual azlactone functionality in PVDMA-treated or film-coated fibers can be exploited to chemically modify the surface chemistry and physicochemical properties of fiber-based materials postfabrication using amine functionalized molecules. For example, we demonstrate that this approach permits control over the surface properties of paper (e.g., absorption of water) by simple postfabrication treatment of film-coated paper with the hydrophobic amine n-decylamine. The azlactone functionality present in these materials provides a platform for the modification of polymer-treated and film-coated fibers with a broad range of other chemical and biological species (e.g., enzymes, peptides, catalysts, etc.). The results of this investigation thus provide a basis for the functionalization of fibers and fiber-based materials (e.g., textile fabrics or nonwoven mats) of potential utility in a broad range of consumer, industrial, and biomedical contexts.