Matching Items (4)
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- All Subjects: chemical engineering
- Creators: Dai, Lenore
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
Description
Iodide-based ionic liquids have been widely employed as sources of iodide in electrolytes for applications utilizing the triiodide/iodide redox couple. While adding a low-viscosity solvent such as water to ionic liquids can greatly enhance their usefulness, mixtures of highly viscous iodide-containing ILs with water have never been studied. Thus, this paper investigates, for the first time, mixtures of water and the ionic liquid 1-butyl-3-methylimidazolium iodide ([BMIM][I]) through a combined experimental and molecular dynamics study. The density, melting point, viscosity and conductivity of these mixtures were measured experimentally. The composition region below 50% water by mole was found to be dramatically different from the region above 50% water, with trends in density and melting point differing before and after that point. Water was found to have a profound effect on viscosity and conductivity of the IL, and the effect of hydrogen bonding was discussed. Molecular dynamics simulations representing the same mixture compositions were performed. Molecular ordering was observed, as were changes in this ordering corresponding to water content. Molecular ordering was related to the experimentally measured mixture properties, providing a possible explanation for the two distinct composition regions identified by experiment.
ContributorsNgan, Miranda L (Author) / Dai, Lenore (Thesis director) / Nofen, Elizabeth (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
Asymmetric polystyrene-gold composite particles are successfully synthesized alongside core-shell composite particles via a one-step Pickering emulsion polymerization method. Unlike core-shell particles which form in the droplet phase of a stabilized Pickering emulsion, asymmetric particles form via a seeded growth mechanism. These composite particles act as catalysts with higher recyclability than pure gold nanoparticles due to reduced agglomeration. With the addition of N-isopropylacrylamide (NIPAAM) monomers, temperature-responsive asymmetric and core-shell polystyrene/poly(N-isopropylacrylamide)-gold composite particles are also synthesized via Pickering emulsion polymerization. The asymmetric particles have a greater thermo-responsiveness than the core-shell particles due to the increased presence of NIPAAM monomers in the seeded-growth formation. Poly(N-isopropylacrylamide) (PNIPAM)-containing asymmetric particles have tunable rheological and optical properties due to their significant size decrease above the lower critical solution temperature (LCST).
ContributorsRabiah, Noelle Ibrahim (Author) / Dai, Lenore (Thesis director) / Torres, Cesar (Committee member) / Zhang, Mingmeng (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2014-05
Description
This study aims to determine the feasibility of producing mechanophore-incorporated epoxy that can be healed. This was accomplished by grafting a synthesized mechanophore into tris(2-aminoethyl)amine to create a new epoxy hardener. Then this branched hardener was combined with a second hardener, diethylenetriamine (DETA). A proper ratio of the branched hardener to the DETA will ensure that the created epoxy will retain the force responsive characteristics without a noticeable decline in both the physical and thermal properties. Furthermore, it was desired that the natural structure of the epoxy would be left in place, and there would only be enough branched hardener present to elicit a force response and provide the possibility for healing. The two hardeners would then be added to Diglycidyl Ether of Bisphenol F (DGEBPF), which is the epoxy resin. The mechanophore-incorporated epoxy was compared to a standard epoxy—just DETA and DGEBPF—and it was determined that the incorporation of the mechanophore led to an 8.2 degrees Celsius increase in glass transition temperature, and a 33.0% increase in cross link density. This justified the mechanophore-incorporated epoxy as a feasible alternative to the standard, as its primary thermal and physical properties were not only equal, but superior. Then samples of the mechanophore-incorporated epoxy were damaged with a 3% tensile strain. This would cause a cycloreversion in the central cyclobutane inside of the mechanophore. Then they were healed with UV light, which would redimerize the severed hardener moieties. The healed samples saw a 4.69% increase in cross-link density, demonstrating that healing was occurring.
ContributorsPauley, Bradley (Author) / Dai, Lenore (Thesis director) / Gunckel, Ryan (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-12
Description
The ability to sense applied damage and correlate it with a measurable signal is extremely desirable in any material application to prevent catastrophic failure and the possible loss of use of the material or human injury. Mechanochemistry, in which mechanical forces induce chemical changes, can allow for targeted damage detection by way of embedded mechanophore units, with certain mechanophore chemistries emitting a fluorescent signal in response an applied force. In this work, we successfully employed microparticles of the mechanophore dimeric 9-anthracene carboxylic acid (Di-AC) in a thermoset polyurethane matrix to study their application as universal stress-sensing fillers in network polymer matrix composites. Under a compressive force, there is bond breakage in the mechanically weak cyclooctane photodimers of Di-AC, such that there is reversion to the fluorescent anthracene-type monomers. This fluorescent emission was then correlated to the applied strain, and the precursors to damage were detected with a noticeable fluorescent signal change at an applied strain of only 2%. This early damage detection was additionally possible at very low particle loadings of 2.5 and 5 wt%, with the 5 wt% loading showing enhanced material properties compared to the 2.5 wt%, due to particle reinforcement in the composite. Overall, the synthesis of Di-AC as a stress-sensitive particle filler allows for facile addition of advanced functionality to these ubiquitous thermoset composites.
ContributorsDasgupta, Avi Ryan (Author) / Dai, Lenore (Thesis director) / Nofen, Elizabeth (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05