Direct functionalization of cellulose nanocrystals with polymer brushes via UV-induced polymerization: access to novel heterogeneous visible-light photocatalysts

Cellulose nanocrystals (CNCs) are an exciting class of bio-based materials attracting increasing interest for a wide range of potential applications due to their nanoscale dimensions, biocompatibility, biodegradability and large surface area. In this work, we report a universal and facile strategy for the preparation of polymer brushes on CNCs via photopolymerization in the absence of any initiator immobilization. The reported procedure is applicable to a series of vinyl monomers, leading to the direct creation of homogeneous and stable polymer coatings on CNCs. Characterization of the resulting polymer-grafted CNCs by FTIR spectroscopy, XRD, AFM and TGA indicates a high grafting density, enhanced dispersing ability and thermal stability without altering the crystalline structure of the intrinsic CNCs. Finally, we have demonstrated the possibility to covalently attach 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene to the grafted polymer chain ends through polymer analogous reactions. The afforded nano-objects show visible-light photocatalytic activity and chemoselectivity in the oxidization reaction of thioanisole to methyl phenyl sulfoxide.