Green and combinational method towards clickable alkynylated cellulose fibers (ACFs)

This paper presents an environmentally friendly strategy to obtain alkynylated cellulose fibers (ACFs), a versatile platform for tailoring cellulose by robust click reaction. This strategy is based on the integration of two efficient reactions: selective oxidation of cellulose fibers by sodium periodate (NaIO₄) generating dialdehyde cellulose fibers and subsequent Schiff base reaction with 3-ethynylaniline yielding alkynylated cellulose fibers (ACFs). The alkynyl moieties introduced into ACFs were simply transferred with azido compounds under Cu(I) catalysis and mild conditions. The content of alkynyl groups of ACFs was found to be as high as 3.0 mmol/g. Fourier transform infrared spectroscopy (FTIR) showed that the selective oxidation of cellulose fibers generated aldehyde groups and the Schiff base reaction resulted in the incorporation of ethynyl groups and benzene rings into cellulose fibers. FTIR and X-ray photoelectron spectroscopy results confirmed the successful click reaction between ACFs and 4-azidobenzoic acid. This clickable platform would serve as a versatile starting precursor for finely tuning cellulose fibers for advanced applications.