Doctoral Defense - Shalin Patil

About the Event

The Department of Chemical Engineering and Materials Science

Michigan State University 

Ph.D. Dissertation Defense 

November 12^th, 2024 at 1:00 PM (EST)

3540 Engineering Building and Zoom

Contact Department or Advisor for Zoom Information

ABSTRACT

Supramolecular Structure and Dynamics of a Class of Hydrogen Bonding Liquids: Monohydroxy Alcohols

By: Shalin Patil
Advisor: Dr. Shiwang Cheng

Hydrogen bonding (H-bonding) is omnipresent such as in DNA, RNA, proteins, and water. The highlighting features of the hydrogen bonding interactions are their directionality and reversibility: the H-bonding has a bond angle between 135o to 180o and they are relatively weak and can break and recombine at experimental time scales. Despite the wide acknowledgment of the directionality and reversibility of H-bonding interactions, their influences on molecular dynamics and macroscopic properties, such as flow or viscosity, have been far from revealed. In this dissertation, we focus on one of the simplest types of H-bonding liquids: Monohydroxy Alcohols (MA) to show how the H-bonding interactions affect the supramolecular structures formation, the supramolecular dynamics (including the Debye relaxation process), and the relationship between these supramolecular structures and viscosity. In particular, we have employed a new experimental testing platform, the rheo-dielectric spectroscopy, that reveals: (i) An interesting relationship between the structural relaxation time, t_α, and the Debye time, t_D, with t_D^2/t_α following an Arrhenius temperature dependence; (ii) The presence of an intermediate relaxation process with characteristic time, t_m, between t_α, and t_D of MAs that is both dielectric and rheology active; (iii) t_m agrees excellently with hydrogen bonding exchange time of MAs from NMR measurements. These observations inspire new theoretical development, i.e. the living polymer model (LPM) (Figure 1), which enables a coherent explanation for a wide range of molecular parameters on the supramolecular structures and dynamics of monohydroxy alcohols, including the roles of molecular architecture, the alcohol types, and the dilution. The results have helped clarify several concepts in the current understanding of the dynamics of H-bonding liquids, such as the supramolecular chain breakup time, the average supramolecular chain size, and the H-bonding lifetime of MAs.

Persons with disabilities have the right to request and receive reasonable accommodation. Please call the Department of Chemical Engineering and Materials Science at 355-5135 at least one day prior to the seminar; requests received after this date will be met when possible.