A new bottlebrush polymer that has two distinct functional groups, catechol and internal ketone, were synthesized via graft-through ring-opening metathesis polymerization (ROMP). A highly-functional macromonomer was synthesized to possess terminal catechol group that links to internal ketone through poly(ethylene glycol) (PEG) segments. Polymerization was carried out via ROMP using third-generation Grubbs’ catalyst resulting controlled degree of polymerization (17 – 500) and narrow PDI values (1.10- 1.46). The internal ketone on the bottlebrush polymers was used to integrate small molecules via oxime ligation. This form of oxime ligation was demonstrated with a series of oxyamines, with degrees of functionalization on the range of 18 – 100 %, while introducing further functionality in the form of azide groups, which were rapidly converted to corresponding triazoles via metal-free click chemistry using the crosslinker (1R, 8S, 9S)-Bicyclo[6.1.0]non-4-yn-9-ylmethyl (BCN) bisfunctionalized PEG (Mn = ~6000 g/mol). Under these conditions, the transformation from soluble polymer solution to soft hydrogel occurs within minutes. The polymer described herein stands testament to the ability of modularly-designed macromonomers to dictate the structure and properties of downstream materials in a predicable fashion. This work makes two important additions to the repertoire of bottlebrush polymers: (1) the first example of a catechol-derived brush adhesive relying on an internal ketone for post-polymerization modification; and (2) the post-polymerization modification is utilized to greatly affect the mechanical properties of the bulk material through oxime functionalization and subsequent metal-free click chemistry beginning from the innocuous, and easily introduced, internal ketone.

Synthesis of multifunctional bottlebrush polymers

255th National Meeting (2018)

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