Cellulose fibers modification through metal-free click chemistry for the elaboration of versatile functional surfaces

In the present work, a novel and versatile way was developed to functionalize cellulose fibers from wipes under heterogeneous conditions. The technic was based on metal-free click chemistry to avoid the persistence of any metal traces on cellulose. First, cellulose fibers were covalently pre-functionalized with bicyclononyne (BCN) to promoted azide-alkyne addition with molecules of interest, like coumarin and beta-cyclodextrin derivatives. X-ray photoelectron microscopy (XPS) shows that one BCN group per cellulose unit was modified at the surface of the wipe. 3-azido-7-hydroxycoumarin that can be used as fluorophore for bio-sensoring applications was efficiently bound to the pre-functionalized cellulose with a yield of reaction estimated at 60%. The addition of 6-azido-per-6-deoxy-beta-cyclodextrin (beta-CD derivative) was investigated in order to target future organophosphorus decontamination properties to cellulose wipes. With the best reaction conditions, 60% of triazole groups corresponding to 4 reactive azido groups per beta-CD derivative were detected by XPS proving the efficiency of the click reaction. The highest DS values were obtained after 96 h for beta-CD 20 Eq (DS = 1.7% by elementary analysis and DS = 2.5% by weight measurements). Scanning electron microscopy observations highlighted a globally well distributed beta-CD with some aggregates on the surface of the fibers. Thus, the pre-functionalized BCN-cellulose fibers could be used for many applications after an easy clicking of target compounds.