Matching Items (4)
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- All Subjects: Organometallic compounds
- All Subjects: Polymers
- Creators: Mu, Bin
Description
Identification of early damage in polymer composite materials is of significant importance so that preventative measures can be taken before the materials reach catastrophic failure. Scientists have been developing damage detection technologies over many years and recently, mechanophore-based polymers, in which mechanical energy is translated to activate a chemical transformation, have received increasing attention. More specifically, the damage can be made detectable by mechanochromic polymers, which provide a visible color change upon the scission of covalent bonds under stress. This dissertation focuses on the study of a novel self-sensing framework for identifying early and in-situ damage by employing unique stress-sensing mechanophores. Two types of mechanophores, cyclobutane and cyclooctane, were utilized, and the former formed from cinnamoyl moeities and the latter formed from anthracene upon photodimerization. The effects on the thermal and mechanical properties with the addition of the cyclobutane-based polymers into epoxy matrices were investigated. The emergence of cracks was detected by fluorescent signals at a strain level right after the yield point of the polymer blends, and the fluorescence intensified with the accumulation of strain. Similar to the mechanism of fluorescence emission from the cleavage of cyclobutane, the cyclooctane moiety generated fluorescent emission with a higher quantum yield upon cleavage. The experimental results also demonstrated the success of employing the cyclooctane type mechanophore as a potential force sensor, as the fluorescence intensification was correlated with the strain increase.
ContributorsZou, Jin (Author) / Dai, Lenore L (Thesis advisor) / Chattopadhyay, Aditi (Thesis advisor) / Lind, Mary L (Committee member) / Mu, Bin (Committee member) / Yu, Hongyu (Committee member) / Arizona State University (Publisher)
Created2014
Description
We report the synthesis of novel boronic acid-containing metal-organic frameworks (MOFs), which was synthesized via solvothermal synthesis of cobalt nitride with 3,5-Dicarboxyphenylboronic acid (3,5-DCPBC). Powder X-ray diffraction and BET surface area analysis have been used to verify the successful synthesis of this microporous material.
We have also made the attempts of using zinc nitride and copper nitride as metal sources to synthesize the boronic acid-containing MOFs. However, the attempts were not successful. The possible reason is the existence of copper and zinc ions catalyzed the decomposition of 3,5-Dicarboxyphenylboronic acid, forming isophthalic acid. The ended product has been proved to be isophthalic acid crystals by the single crystal X-ray diffraction. The effects of solvents, reaction temperature, and added bases were investigated. The addition of triethylamine has been shown to tremendously improve the sample crystallinity by facilitating ligand deprotonation
We have also made the attempts of using zinc nitride and copper nitride as metal sources to synthesize the boronic acid-containing MOFs. However, the attempts were not successful. The possible reason is the existence of copper and zinc ions catalyzed the decomposition of 3,5-Dicarboxyphenylboronic acid, forming isophthalic acid. The ended product has been proved to be isophthalic acid crystals by the single crystal X-ray diffraction. The effects of solvents, reaction temperature, and added bases were investigated. The addition of triethylamine has been shown to tremendously improve the sample crystallinity by facilitating ligand deprotonation
ContributorsYu, Jiuhao (Author) / Mu, Bin (Thesis advisor) / Forzani, Erica (Committee member) / Nielsen, David (Committee member) / Arizona State University (Publisher)
Created2014
Description
The search for highly active, inexpensive, and earth abundant replacements for existing transition metal catalysts is ongoing. Our group has utilized several redox non-innocent ligands that feature flexible arms with donor substituents. These ligands allow for coordinative flexibility about the metal centre, while the redox non-innocent core helps to overcome the one electron chemistry that is prevalent in first row transition metals. This dissertation focuses on the use of Ph2PPrDI, which can adopt a κ4-configuration when bound to a metal. One reaction that is industrially useful is hydrosilylation, which allows for the preparation of silicones that are useful in the lubrication, adhesive, and cosmetics industries. Typically, this reaction relies on highly active, platinum-based catalysts. However, the high cost of this metal has inspired the search for base metal replacements. In Chapter One, an overview of existing alkene and carbonyl hydrosilylation catalysts is presented. Chapter Two focuses on exploring the reactivity of (Ph2PPrDI)Ni towards carbonyl hydrosilylation, as well as the development of the 2nd generation catalysts, (iPr2PPrDI)Ni and (tBu2PPrDI)Ni. Chapter Three presents a new C-O bond hydrosilylation reaction for the formation of silyl esters. It was found the (Ph2PPrDI)Ni is the most active catalyst in the literature for this transformation, with turnover frequencies of up to 900 h-1. Chapter Four explores the activity and selectivity of (Ph2PPrDI)Ni for alkene hydrosilylation, including the first large scope of gem-olefins for a nickel-based catalyst. Chapter Five explores the chemistry of (Ph2PPrDI)CoH, first through electronic structure determinations and crystallography, followed by an investigation of its reactivity towards alkyne hydroboration and nitrile dihydroboration. (Ph2PPrDI)CoH is the first reported cobalt nitrile dihydroboration catalyst.
ContributorsRock, Christopher L (Author) / Trovitch, Ryan J (Thesis advisor) / Kouvetakis, John (Committee member) / Pettit, George R. (Committee member) / Arizona State University (Publisher)
Created2018
Description
Polymer-nanoparticle composites (PNCs) show improved chemical and physical properties compared to pure polymers. However, nanoparticles dispersed in a polymer matrix tend to aggregate due to strong interparticle interactions. Electrospun nanofibers impregnated with nanoparticles have shown improved dispersion of nanoparticles. Currently, there are few models for quantifying dispersion in a PNC, and none for electrospun PNC fibers. A simulation model was developed to quantify the effects of nanoparticle volume loading and fiber to particle diameter ratios on the dispersion in a nanofiber. The dispersion was characterized using the interparticle distance along the fiber. Distributions of the interparticle distance were fit to Weibull distributions and a two-parameter empirical equation for the mean and standard deviation was found. A dispersion factor was defined to quantify the dispersion along the polymer fiber. This model serves as a standard for comparison for future experimental studies through its comparability with microscopy techniques, and as way to quantify and predict dispersion in polymer-nanoparticle electrospinning systems with a single performance metric.
ContributorsBalzer, Christopher James (Author) / Mu, Bin (Thesis director) / Armstrong, Mitchell (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12