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. To address the links between design, in situ functionalization and properties, layers of end-tethered polymer chains, or polymer brushes, were created by grafting chains of poly(4,4-dimethyl-2-vinylazlactone) (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 set brush structure. The results indicate that the grafting density of chains and size of the functionalizing agent play major roles in governing the extent of functionalization, and with all but the smallest functionalizing agents, reactive modification is incomplete. In addition to developing an average view of the in situ functionalization, 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 provide perspectives on the relationship between extent of reaction in the confined environment, display of functional motifs, and 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 functionalization of azlactone-based polymer brushes

249th National Meeting (2015)

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