Orthogonal Multifunctionalization of Random and Alternating Copolymers

A series of copolymers with varying degrees of alternation are synthesized by free-radical polymerization from 2,3,4,5,6-pentafluorostyrene (PFS) and propargyl-containing styrene derivatives. The degree of alternation varied with the electronic nature of the styrene derivative: random copolymers were obtained using monomers with electron withdrawing moieties, whereas increasingly alternating copolymers were obtained by increasing the electron donating nature of the substituent. The copolymers could be functionalized in an orthogonal fashion using a nucleophilic substitution (with thiols) to functionalize PFS and the copper-catalyzed 3 + 2 cycloaddition between azides and the alkyne of the propargyl groups. This methodology allows for the facile synthesis of functional alternating copolymers.

Orthogonally reactive SAMs as a general platform for bifunctional silica surfaces

We report the synthesis and self-assembly of azide and amine trimethoxysilanes that result in mixed monolayers on silica. The amine and azide functional groups can be independently reacted with acid chlorides and terminal alkynes, respectively. Consequently, these orthogonally reactive monolayers represent a general starting point for making bifunctional surfaces. Using X-ray photoelectron spectroscopy, we determined the azide/amine surface ratio as well as the reactivity of the azide and amine functional groups in the mixed self-assembled monolayer (SAM). Significantly, the surface azide/amine ratio was much lower than the azide/amine ratio in the self-assembly mixture. After determining the self-assembly mixture composition that would afford 1:1 azide-amine mixed monolayers, we demonstrated their subsequent functionalization. The resulting bifunctional surface has a similar functional group ratio to the azide/amine precursor SAM demonstrating the generality of this approach.