Preparation, functionalization and derivation of nanocrystalline cellulose

Abstract

Nanocrystalline cellulose (NCC) and its modified green products recently have gained the attention of the scientific community due to their potential applications in electronics, nanocomposite films, drug delivery, protein immobilization, metallic reaction template, pharmaceuticals, cosmetics, and personal cares. In this study, nanocrystalline cellulose (NCC) was prepared from microcrystalline cellulose (MCC) through strong acid hydrolysis viz. sulfuric acid, hydrochloric acid and a mixture of sulfuric acid and hydrochloric acid. It was observed that at H2SO4 concentration of 63% -65%, a clear stable transparent gel formed which on drying results transparent film. To functionalalize nanocrystalline cellulose, different chemical modifications like oxidation, reduction, schiff’s base formation and hyrdazone formation were carried out. NCC was converted to dialdehyde nanocellulose (DANC) with regioselective sodium meta periodate oxidizing agent. That dialdehyde nanocellulose was further converted to dicarboxylated and trihydroxyl nanocellulose with the selective sodium chlorite as oxidizing agent and sodium borohydride as reducing agent respectively. DANC was further derivatized with some primary aliphatic amines (ethylene diamine and hydroxyl amine hydrochloride) and some aromatic amines (aniline, 4-nitroaniline and 4-hydroxyaniline) via reductive amination. Surface morphology and particle size were investigated through Field Emission Scanning Electron Microscopy (FESEM). The analysis showed that all the cellulosic materials are in the form of nanofiber and the average fiber diameter of NCC and other modified NCC were less than 20 nm with a length of 100 nm to few micrometers. The results of chemical analysis, FTIR and 1HNMR spectra confirmed the conversion of NCC to different functional groups and amine derivatives. Thermogravimetric analysis results showed that the modified NCCs have higher thermal stability than NCC. The NCC and its all modified products are crystalline in nature where crystallinity index of modified NCCs was decreased compare to NCC. Surface charges were increased for the oxidized products of NCC. The optical transparency was examined in the visible range which showed that the transparency increased for all the modified NCC which suggests that all the modified NCCs are more dispersive than NCC in aqueous medium.