Molecular Insight into Cellulose Nanocrystals and their Interaction with Cellulosic Oligomers by All-Atom Simulation

Abstract

Cellulose nanocrystal (CNC) has found application in a variety of novel products due to its spectrum of properties. Notably, the CNC-polymer systems have seen numerous applications in special materials like Pickering emulsions, foams and gels etc. CNC interacts with different polymers to a different extent. These interactions include molecular level and bulk interactions. Subsequently, they modify the interfacial properties. Though vibrant, the CNC-polymer molecular interaction is still unclear. We took this void in our understanding as our motivation to explore these interactions. In this work, we tried to understand why CNC interacts differently with different polymers and what drives the adsorption of polymer on CNC. Our work can also help us to understand the configurations and origins of CNC-polymer system properties. The broad range of length and time scales covered by this physical process requires a multiscale simulation approach. In this thesis, we start with the all-atom molecular simulation and focus on the specific energetic interactions between CNC surfaces and unrealistically short polymer chains. In future work, we will build on this model and develop a multiscale modeling approach for capturing the full scope of CNC-polymer interaction, including the configuration and dynamics of realistic long polymer chains around CNCs. We propose that there are two driving forces for adsorption based on the free energy difference values obtained via PMF (potential of mean force) calculations done on eight systems with different physical components. Overall, we conclude that the balance between polymer's ability to form hydrogen bonds with the surface and their interactions with the bulk solvent control the adsorption and desorption phenomenon. A larger coarse-grained model developed from our simulations will help to understand these systems better. This presented work deals with the specific energy interactions and information which we will need for the systematic coarse-graining of these systems.