Master of Science (MS), Ohio University, 2017, Mechanical Engineering (Engineering and Technology)

Evaporation of water in hydrophobic confinement has been a subject of numerous studies because of its key role in functioning and self-assembly of many biologically relevant systems, such as protein folding, formation of lipid bilayers, operation of ion channels, etc. Evaporation is an activated process and hence is a rare event in molecular time-scales. There is no consensus on a continuum thermodynamic theory which captures different aspects of the process satisfactorily. We study the simple case of evaporation of water confined between two rigid hydrophobic walls of tunable hydrophobicity, and adopt nucleation theory as our continuum thermodynamic approximation. We propose analytical expressions for free energy barrier and size of the critical vapor tube necessary for evaporation to occur. In the theory, we incorporate the effect of line tension, that has been neglected so far. To validate the expressions and explore role of line tension, we obtain free energy barriers and critical radii to evaporation from molecular simulations, by employing Indirect Umbrella Sampling (INDUS) and committor probability analysis methods. By comparing the results from simulations and theory, we find that the role of line tension is crucial in evaporation of water in hydrophobic confinement.

Committee: Sumit Sharma Dr. (Advisor); Horacio Castillo Dr. (Committee Member); Sarah Hormozi Dr. (Committee Member); Keerti Kappagantula Dr. (Committee Member) Subjects: Chemical Engineering