Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Rai, Neeraj

Committee Member

Kundu, Santanu

Committee Member

Archibald, Christopher

Committee Member

Meng, Dong

Date of Degree

12-13-2019

Original embargo terms

Worldwide

Document Type

Dissertation - Open Access

Major

Chemical Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Dave C. Swalm School of Chemical Engineering

Abstract

Molecular simulations are computer experiments that allow us to investigate thermodynamic and transport properties of complex chemical systems. Here, we have investigated self-assembly of organogelators and analysed the diffusion characteristics of small molecules in the nanopores of zeolites. Molecular gels are attractive soft-materials with viscoelastic properties with applications in drug delivery, tissue engineering, sensing, etc. Small organic amphiphilic gelators act as a building block of complex 3-dimensional network in molecular gels. Due to time and length scale differences, the understanding and characterization of early stage aggregation of gelators is difficult using experimental techniques. Classical and quantum mechanical approaches have been used to understand the self-assembly of gelator molecules and to rationalize the gelation. We have used density functional theory (DFT) to derive new quantity namely, pseudo-cohesive energy density to rationalize the gelation of di-Fmoc-L-lysine. Molecular dynamics is used to probe the self-assembly and conformation of gelators in DMSO-water. We have also studied the self-assembly of 12-hydroxyoctadecanamide in octane. We used DFT to calculate the dimer energy in the vacuum and meta-dynamics simulation to calculate potential of mean force in the condensed phase. Interestingly, we found that, dimer energetics was not sufficient to elucidate bulk aggregation behavior, such as, probability distribution of different dimers in aggregation. We also observed different types of branched and mesh-like networks in the aggregation, which are analogous to the network found through experimental imaging techniques. Zeolites are crystalline materials with well defined nanoporous channels and act as molecular sieves. They are attractive for catalytic applications due to their tunable Bronsted and Lewis acidity. A wide array of zeolite polymorph offers versatile micro and meso-porous channels to accommodate small molecules like glucose to big and complex lignocellulose molecules for undergoing chemical transformations. In this current study, we present the transport properties of -glucose into Faujisite zeolite framework. We have investigated the trajectory of the glucose molecule into porous material and found that, the diffusivity of glucose inside zeolite pore is two order of magnitude smaller than that of bulk solutions. We have also observed the variable loading rate of glucose molecule inside pore at different temperatures.

URI

https://hdl.handle.net/11668/16472

Comments

Self-assembly||molecular gels||Zeolite||diffusion

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