Title
Effects of reaction conditions on the shape and crystalline structure of cellulose nanocrystals
Authors
ALINE MERLINI VANDERLEI C. DE SOUZA ROSE M. GOMES ANDRE COIROLO SIMONE MERLINI and RICARDO A. F. MACHADO

Received April 23, 2017
Published Volume 52 Issue 5-6 May-June
Keywords cellulose, acid hydrolysis, crystallinity, cellulose nanocrystals, cellulose polymorphs

Abstract
The properties and possible applications of cellulose nanocrystals (CNCs) are directly associated with their shape and crystalline structure. In this context, the objective of the present work was to evaluate the influence of acid hydrolysis conditions on the morphology and crystalline structure of CNCs. The variables for hydrolysis conditions were the following: acid concentration (50 and 55% v/v), time (20 and 30 min) and reaction temperature (35 °C and 45 °C). The materials obtained were characterized and their yields were determined. Investigations on the shape and dimensions of the CNCs were carried out using transmission electron microscopy (TEM). In addition, X-ray diffraction analyses were performed to obtain information on the crystallinity and the polymorphic state of nanocrystals. Regardless of acid concentration and reaction time, the formation of spherical nanocrystals was observed with a mixture of the cellulose crystal structures I and II in different proportions in the reactions conducted at 35 °C. For the reactions conducted at 45 °C, predominantly rod-shaped nanocrystals with a cellulose I crystal structure were obtained.