Probing interfacial interactions: Ionic liquids and cellulose thin films

The efficient processing of cellulosic materials with ionic liquids heavily relies on the initial contact and wetting phase, which are crucial yet poorly understood in many ionic liquid/cellulose interactions. In this study, we explore these interactions through comprehensive wetting experiments and a robust mathematical framework. By leveraging molecular-kinetic theory (MKT), we illuminate the key factors affecting these interactions, such as viscosity and ion pair volume, and identify specific cellulose chain groups involved in the process. Our findings confirm that ionic liquids selectively adsorb on active sites of cellulose, facilitating a dynamic adsorption-desorption mechanism crucial for forward movement. Notably, we have identified these adsorption sites to be approximately 5 to 20 Å apart, e.g., distances between neighboring C₆-hydroxyl groups within a cellulose molecule. Furthermore, our results demonstrate that the dynamics of jump frequencies are intrinsically linked to the properties of ionic liquids, yet influenced by a complex array of parameters. This study provides significant insights into manipulating the interaction mechanisms to enhance spreading efficiency on surfaces. Our research underscores the pivotal role of cellulose's chemical structure and order, offering valuable implications for improving high-throughput processing techniques in various industrial applications.