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Dryad

Towards bio-inspired polymer adhesives: Activation assisted via HOBt for grafting of dopamine onto poly(acrylic acid)

Abstract

The design of bio-inspired polymers has long been an area of intense study, however applications to the design of concrete admixtures for improved materials performance have been relatively unexplored. In this work we functionalized poly(acrylic acid) (PAA), a simple analogue to polycarboxylate ether admixtures in concrete, with dopamine to form a catechol-bearing polymer (PAA-g-DA). Synthetic routes utilizing hydroxybenzotriazole (HOBt) as an activating agent were examined for their ability in grafting dopamine to the PAA backbone. Previous literature using the traditional coupling reagent 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) to graft dopamine to PAA were found to be inconsistent and the sensitivity of EDC coupling reactions necessitated a search for an alternative. Additionally, HOBt allowed for greater control over percent functionalization of the backbone, is a simple, robust reaction, and showed potential for scalability. This finding also represents a novel synthetic pathway for amide bond formation between dopamine and PAA. Finally, we performed preliminary adhesion studies of our polymer on rose granite specimens and demonstrated a 56% improvement in the median adhesion strength over unfunctionalized PAA. These results demonstrate an early study on the potential of PAA-g-DA to be utilized for improving the bonds within concrete.