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A facile way for concurrent fabrication and surface functionalization of cellulose nanofibrils by lactic acid mediated catalysis
- Rahim A. Rafi
- Cellulose nanofibers (CNFs) have great potential to use in various applications. Different methods like mechanical agitation and enzymatic approaches are used for preparation of CNFs; however, high energy consumption, using expensive and harsh chemicals are the main drawbacks of these methods. Herein, we report an environmentally friendly one-step reaction approach to produce lactic acid (LA) functionalized CNFs from wood-derived pulp fibers in high yields. This is done by transforming pulp fibers to nanofibrillated “cellulose lactate” under mild conditions, using LA as reaction media and catalyst. The fabricated LA functionalized CNFs was characterized by different techniques like FT-IR, SEM, solid states CNMR, TGA. Low degree of substitution suggested surface functionalization of CNFs. It was also noticed that adding a mineral acid as co-catalyst reduced fabrication yields. Hence, the autocatalytic esterification and cellulose hydrolysis occurred without using metal based or a harsh mineral acid catalysts. The LA media is successfully recycled in multiple reaction cycles producing the corresponding CNFs in high yields. Moreover, the LA groups attached onto CNFs can be removed by cleavage of the ester bonds via alkali hydrolysis. The film made of LA functionalized CNFs showed slightly higher hydrophobicity and mechanical strengths compared with the film made of CNFs. Moreover, the fabricated CNFs were used to make nanocomposites of ethylenebrassylate (EB) and adding 1 wt.% LA-CNFs or CNFs, enhanced the tensile strengths of neat poly EB by 55 and 44%, respectively. The FTIR and solid states CNMR also confirms the covalent bonding of PEB onto the CNFs.
