A Systematic Study of Fatty Acids Interacting with Crystalline Cellulose Surfaces via Molecular Dynamics Simulations

The oily soiling of the cellulosic textile has been evaluated in this research. The complex problem has been evaluated based on application-specific context. To characterize the relationship of fatty acids with cellulose surfaces its wetting characteristics has been investigated by using fatty acid droplet and film. Effect of fatty acid chemistry has been evaluated in the context of natural variability of fatty acids found in both processing and usage. Effect of temperature variation has also been investigated due to its critical significance in fatty acid coating on food packaging material usage.;Molecular dynamics simulation has been applied to characterize the important aspects of cellulose surface properties such as roughness, hydrophilicity and oleophilicity on its fatty acid based soil adhesion. Increased roughness in the form of increased molecular surface area allows higher adsorption of fatty acid films. Formation of hydrogen bonding and increased local order are the drivers behind this process. A practical implication of this research can be observed through roughening of surfaces in plasma processing. Both hydrophilicity and oleophilicity of the of the cellulose surface was determined by using nano droplets of water and fatty acid. The results indicated that the cellulose surface possessed strong hydrophilicity and slight oleophilicity, which is influenced by its surface roughness, number of hydrogen bonds and accessibility of the functional groups at the surface. This research can be applied for predicting wettability of the unknown surfaces using known liquid nano-droplets.;The impact of fatty acid adhesion due to its chemistry, indicated that the length of the fatty acid chains greatly influence its adsorption on cellulosic surfaces. The degree of fatty acid unsaturation has negligible influence on its adsorption. The alignment of fatty acid chains can allow higher packing. A practical implication of this research is choice of fatty acid chemistry to control moisture-vapor permeability through packaging materials.;The thermal instability of the fatty acid coatings at higher temperature was investigated as part of this research. The results from the simulation indicated that the fatty acid film is stable over the range of usable temperature of 400 K and there is a possibility of slight desorption at misuse temperature such as 450 K. The cellulose structure remained intact throughout this temperature range. It was also found that the stability of coating is highly dependent on its thickness. There is a higher possibility of desorption from the thick film then the thin and annealed films. The hydrogen bonding has been identified as the key driver behind fatty acid film stability. From the simulation it was also understood that regardless of the thickness and film construction, higher number of hydrogen bonding between oil and the surface can reduce the possibility of desorption from the cellulose-fatty acid film complex.