Reactive modification of polymer thin films provides a useful route to confer new properties to the underlying material, with the range, strength and type of interaction across the interface dictated by the display of functional groups decorating the surface. The design and development of gradient surfaces is an efficient technique to control and optimize the extent of chemical functionality for surface modifications that is useful for tuning properties. To address the links between design, in situ gradient functionalization and properties, layers of end-tethered polymer chains, or polymer brushes, were created by grafting chains of poly(glycidyl methacrylate)-block-(2-vinyl-4,4-dimethylazlactone) (PGMA-b-PVDMA) onto silicon substrates. The pendant azlactone rings of PVDMA readily react with nucleophiles, allowing in situ functionalization to be studied through the use of ellipsometry and neutron reflectivity measurements as a function of parameters that affect brush structure. The results indicate that the grafting density of chains and size of the functionalizing agent govern the extent of functionalization. In addition to an average view of the in situ functionalization process through ellipsometry, the sensitivity of neutron scattering methods to isotopic substitution (of D for H) provides insight into the location of functional groups installed within the PVDMA brush by reactive modification. These studies yield relationships between extent of reaction in the confined environment, the spatial display of functional motifs, and the swelling properties of the interfacial layer, as well as insight into general strategies that can be used to tailor frictional, adhesive, or biomimetic properties of polymer thin films.

In situ gradient functionalization of azlactone-based block copolymer brushes

253rd National Meeting (2017)

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