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Azlactone-Functionalized Polymers: Reactive Platforms for the Design of Advanced Materials

Polymers functionalized with azlactone (or oxazolone) functionality react via rapid and efficient ring-opening reactions with a variety of different nucleophilic species (e.g., primary amines, hydroxyl groups, and thiol functionality), and, as such, can serve as ‘reactive’ platforms for the introduction of chemical and biological functionality. Despite the general versatility and potential practical advantages of this approach, azlactone-functionalized polymers have not been investigated or characterized as broadly as several other classes of commonly used reactive polymers (e.g., polymers containing N-hydroxysuccinimide or pentafluorophenyl groups, etc.). Our group has investigated and leveraged the reactivity of azlactone-functionalized polymers to develop new approaches to (i) the rapid and modular synthesis of side-chain functionalized polymers, and (ii) the fabrication of new chemically reactive surfaces, interfaces, and membranes.

With respect to new approaches to the synthesis of functional polymers, we have used azlactone-functionalized polymers [e.g., poly(2-vinyl-4,4-dimethylazlactone), PVDMA] as templates for the parallel synthesis of libraries of polymers, for the modular synthesis of new amphiphilic copolymers, and as scaffolds for the synthesis of new ‘charge shifting’ cationic polymers (discussed in more detail here).

As part of a broader effort to develop new approaches to the design of reactive surfaces and interfaces, our group has also developed methods for the ‘reactive’ layer-by-layer assembly of polymer multilayers using azlactone-functionalized polymers. This approach builds upon methods developed for the aqueous layer-by-layer fabrication of charged polymers (discussed in more detail here). However, rather than stepwise aqueous assembly mediated by ionic interactions, our ‘reactive’ approach is mediated by fast, interfacial organic reactions between azlactone-functionalized polymers and polymers containing primary amine functionality. This approach preserves many of the practical advantages of conventional layer-by-layer assembly, but results in the formation of covalently-crosslinked multilayers and, more importantly, films with residual reactive azlactone functionality that can be used to covalently immobilize other agents by simple post-fabrication treatment with a range of amine-functionalized nucleophiles.

This approach permits fabrication of reactive conformal films on the surfaces of planar or complex substrates and interfaces (e.g., paper, commercial wound dressings, 3-D microwell arrays, water-soluble substrates, and liquid/liquid interfaces created between organic and aqueous phases). It also provides a straightforward and practical platform for further functionalization, patterning, and modulation of the physicochemical properties of these film-coated interfaces (e.g., to modulate water contact angles, create superhydrophobic surfaces, design functional membranes, or to spatially pattern chemical motifs that promote or prevent cell adhesion, protein adsorption, or bacterial biofilm growth). In addition to new avenues of research that continue to arise from our fundamental studies of these new materials, many of the functional films fabricated using this ‘reactive’ approach to assembly provide platforms for other research efforts in our group focused on the design of functional surfaces and interfaces.

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