Synthesis and characterization of methyl acrylamide cellulose nanowhiskers for environmental applications

Cellulose is the most abundant biopolymer on earth with excellent mechanical strength, biocompatibility, and biodegradability. Yet, its poor chemical reactivity deceives its application in various biotechnological sectors. In this study, the microcrystalline cellulose was used as low cost substrate for the synthesis of cellulose nanowhiskers (CNWs) using controlled acid hydrolysis. In order to improve their chemical reactivity, synthesized CNWs were modified with carboxyl functional groups using 2,2,6,6-Tetramethylpiperidinyloxyl (TEMPO) mediated oxidation reaction. These carboxylated cellulose nanowhiskers (CCNWs) were functionalized with amine functional groups using carbodiimide reaction. The as-synthesized amine terminated amido-cellulose nanowhiskers (ACNWs) were modified with methyl acryl functional groups using Michael addition resulting methyl acryl functionalized amido-cellulose nanowhiskers (MAACNWs). The synthesized MAACNWs were characterized using Fourier-transform infrared spectroscopy, UV-visible spectroscopy and nuclear magnetic resonance spectroscopy. The physical morphology was studied using Atomic force microscopy, X-Ray Diffraction and zeta analyser. The modified cellulose nanowhiskers were found to exhibit 4 folds increased surface roughness confirming fabrication of negatively charged chemical groups on CNWs yielding 7 folds higher surface charge than pristine nanowhiskers. Hence, the modified CNWs could be acknowledged as potential candidate for effective heavy metal biosorption and remediation studies.