An Atomic Force Microscopy Study of the Local Hygro-expansion Behavior of Cellulose Microfibrils

Abstract

Structure-property relationships of cellulose-based materials including paper, micro- and nano-fiber composites are often strongly influenced by environmental variables. The interaction of polymeric and crystalline structure in cellulose bio-based materials is of high technological importance. Therefore, understanding the underlying mechanism of environmental/material interactions is crucial for engineering products from bio-based materials. This study was undertaken in an effort to develop a technique for the assessment of dimensional stability of cellulose microfibrils as a function of different relative humidity. Analysis of atomic force microscopy images showed that the local dimensional properties of cellulose microfibrils are highly responsive to variable relative humidity, and their hygro-expansive behavior depends on the relative humidity history, and their method of preparation. The results obtained suggested that dimensional and hygro-expansive behaviors of cellulose microfibrils are related to their ultra-structural arrangements and their origin, either directly or indirectly. These findings, hopefully, will prompt an open discussion regarding the dynamic interactions between cellulose and water molecules at a nano-scale.