Alkylation of mixed micro- and nanocellulose to improve dispersion in polylactide

To improve the dispersion of cellulose particles in a polylactide matrix, a long hydrophobic alkyl chain was substituted for hydrogen of the hydroxyl group of cellulose. Nanocellulose tends to be aggregated due to the hydrogen bonding between three of the hydroxyl groups in each repeat unit, resulting in poor dispersion in non‐polar polymer matrices. In this research, to improve the dispersion of cellulose particles in a polymer matrix, a long hydrophobic alkyl chain was substituted for hydrogen in the hydroxyl group of cellulose via a bimolecular nucleophilic substitution (SN2) reaction with alkyl bromide. Octyl (C8H17) and dodecyl (C12H25) groups were applied in this reaction, which is faster and simpler than other substitution reactions. The chemical structures of octyl and dodecyl ether cellulose were identified using Fourier transform infrared and NMR analyses. The contact angle with water and methylene iodide was measured to calculate the surface energy of alkyl nanocellulose. The surface energy was decreased by the substituted alkyl chain. The thermal properties, morphology and crystal structure of octyl and dodecyl ether cellulose were also investigated to determine the possibility of use as a reinforcement. Furthermore, polylactide/alkyl ether cellulose composites were prepared to make certain of sufficient dispersion of the alkyl ether cellulose in the polylactide matrix. The thermal and mechanical properties of the polylactide composite films were investigated. The optical transmittance of the polylactide composites was measured to confirm the relative dispersity. © 2014 Society of Chemical Industry