Murray State Theses and Dissertations

Abstract

ABSTRACT

The polymerization process of, and gas absorption by, imidazolium-containing thiol:ene poly (ionic liquid)s (PILs), prepared from bisallylimidazolium bis(trifluoromethyl sulfonyl)imide [NTf2-] and pentaerythritoltetrakis(3 mercaptopropionate), was studied. The thiol:ene PILs examined were recently reported by groups at Murray State University. The advantage of thiol:ene PILs over other reported PILs is that thiol:ene polymers are made rapidly by UV exposure and exhibit high mechanical and thermal stability due to high cross-linking. The properties of interest for the thiol:ene PILs were studied using a quartz crystal microbalance (QCM). QCM techniques are based on the piezoelectric effect, where certain crystals (e.g., quartz) will oscillate mechanically (vibrate) under an oscillating electrical potential. The frequency of crystal vibration has been shown to depend on the properties of the environment of the crystal surface, including adsorbed mass, and both the density and viscosity of the surrounding fluid. The frequency of vibration can be measured with such high sensitivity that QCM has picogram detection limits.

There are three major models which were applied to the data obtained in this project: Sauerbrey’s equation, Kanazawa’s equation, and an equation combining Henry’s Law and Sauerbrey’s equation. Sauerbrey’s equation is the simplest model used to evaluate mass changes in thin, rigid films. Many cases do not fulfill the requirement for Sauerbrey to be valid (e.g. thick, viscoelastic films). Therefore, other models have been employed. For example, in liquid contact measurements Kanazawa’s equation is used to measure density and viscosity changes. In some measurements of gas absorption by ionic liquids, an equation derived from Sauerbrey and Henry’s Law has been used to determine gas solubilities.

The polymerization process for five thiol:ene ratios was studied. Bisallylimidazolium was mixed in various ratios pentaerythritol tetrakis(3-mercaptopropionate) (PTMP), along with ~1 wt% of the photoinitiator 2,2-dimethoxy-2-phenyl-acetophenone (DMPA). The mixture was shaken until homogeneous and spin coated onto a QCM crystal. After the chip was loaded into the QCM, instrument frequency was monitored until an equilibrium response was obtained. The crystal then was exposed to UV light until re-equilibration. From the measured data, both the rate of frequency change/polymerization, and change in ρL (density) and ηL (viscosity) could be obtained.

Gas absorption by PILs was also studied. Monomers were prepared and spin coated onto the crystal as before. Then, before loading into the QCM instrument, photopolymerization was performed. In these experiments, the instrument was placed inside an airtight chamber that could be evacuated and filled with the desired gas. After crystal vibration achieved equilibrium the chamber was subjected to vacuum then filled with either CO2 or N2. Based on change of quartz oscillation frequency (Δf) between vacuum and CO2/N2 filled, the various models mentioned earlier could be applied. Then, the relative absorption/solubility of the gases by the various thiol:ene polymers could be determined.

Year manuscript completed

2017

Year degree awarded

2017

Author's Keywords

Ionic liquid and poly(ionic liquid)

Degree Awarded

Master of Science

Department

Chemistry

College/School

Jesse D. Jones College of Science, Engineering and Technology

Dissertation Committee Chair

Robert Daniel Johnson

Thesis Advisor

Robert Daniel Johnson

Committee Chair

Robert Daniel Johnson

Committee Member

Harry B. Fannin

Committee Member

Kevin M, Miller

Committee Member

Rachel Allenbaugh

Document Type

Thesis

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