Study of xylan and cellulose interactions monitored with solid-state NMR and QCM-D

Abstract

Abstract Development of physical properties of bleached eucalyptus kraft pulp is typically based on the refining process. However, many studies have reported that xylan deposition is a viable alternative. As the mechanisms of xylan and cellulose interactions are not clear, the main goal of this study was to achieve a better understanding of these interactions. Considering that a sample of pulp enriched with xylan is a very complex matrix, a model system was developed. Cellulosic thin films were prepared by spincoating and the Langmuir-Schaefer (LS) method from trimethylsilylcellulose (TMSC). Their interactions with xylan were analyzed using the quartz crystal microbalance with dissipation (QCM-D) monitoring technique. The topological changes on cellulose were studied using atomic force microscopy (AFM). For the 13C solid-state nuclear magnetic resonance (NMR) studies, samples were prepared using commercial microcrystalline cellulose (MCC) and xylan. The xylan was extracted from bleached birch kraft pulp using a cold caustic extraction (CCE) method. The QCM-D monitoring showed deposition only with higher concentrations of xylan solution (1 mg · l−1) for the LS method. The AFM images showed that xylan deposits as agglomerates on the cellulose surface, and the NMR experiments showed that there are interactions for the more ordered region of the cellulose fiber and for the less-ordered region.