CO2-Switchable Foaming Agents
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Authors
Poole, Hailey
Date
Type
thesis
Language
eng
Keyword
CO2 switchable surfactants , Foam
Alternative Title
Abstract
The work presented in this thesis focuses on expanding the use of CO2-triggered switchable surfactants for switchable foam stability. Three CO2-responsive switchable cationic surfactants (SCS) with switchable heads were first explored namely, two acetamidines and one dimethylalkylamine. Acetamidine surfactants were found to be inappropriate for foam studies as they hydrolyze when added to water. However, it was possible to study the foam properties of N,N-dimethyltetradecylamine (C14DMA) in the presence and absence of CO2. In the absence of CO2, C14DMA is a water insoluble organic molecule unable to generate foam. In the presence of CO2, the dimethylalkylamine head group becomes protonated and transforms C14DMA into a cationic surfactant that is able to generate foam with moderate stability. Note that the use of CO2 as the dispersed gas always leads to unstable foams due to its high solubility in water resulting in fast coarsening. More stable foams are thus generated with the protonated surfactant and a less soluble gas such as N2. However, continuous N2 dispersion eventually displaces the CO2 in the solution thus deprotonating and “deactivating” the surfactant. Therefore a new class of CO2-switchable surfactants were synthesized to stabilize foams in the presence of an inert gas, such as N2, and prevent foam generation in the presence of CO2. This new class is called CO2-responsive cationic tail switchable surfactants (STSs). These surfactants have a typical polar head group (either cationic, anionic, or non-ionic) while the CO2-responsive group is placed in the middle of the hydrocarbon tail. With aqueous solutions of these molecules one can generate foam with N2. In the presence of CO2, the trialkylamine becomes protonated and disrupts the amphiphilic nature of the surfactant molecules, thus eliminating or decreasing the surfactants ability to produce foam. The STSs synthesized and investigated in this thesis were 5-(heptyl(methyl)amino)-N,N,N-trimethylpentan-1-aminium bromide (C12N(Me)TAB), sodium 4-(methyl(octyl)amino)butane-1-sulfonate (C12N(Me)SSn), and 8-(butyl(methyl)amino)octyl-myo-inositol (C12N(Me)I). To understand the foaming properties of these surfactants, the time evolution and the structure (liquid fraction, bubble size, and bubble size distribution) of the foams generated were studied.
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CC0 1.0 Universal
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
CC0 1.0 Universal