A copolymer of maleic anhydride and styrene is functionalized with Diels–Alder (DA) capable pendant groups to enable the study of this material with different crosslink densities. This constituent is synthesized using commercially available starting materials and relatively simple and uncomplicated chemistries which open the possibility for its use in large-scale applications. The 10%, 25%, 50%, and 100% DA nominal crosslinking based on available pendant furan groups on the polymeric component is investigated. The reaction kinetics are monitored using infrared spectroscopy and rheology. Based on the rheological results, carbon nanotube (CNT) incorporation into the DA matrix is explored in order to determine its effects on the complex modulus of the material. This work done in this report is meant as a proof of concept for this DA material with the possibility of its incorporation into other commonly used bulk materials and/or adhesives to allow for an easily reversible product formulation.
A report meant to document the chemistries investigated by the author for covalent surface modification of CNTs. Oxidation, cycloaddition, and radical reactions were explored to determine their success at covalently altering the CNT surface. Characterization through infrared spectroscopy, Raman spectroscopy, and thermo gravimetric analysis was performed in order to determine the success of the chemistries employed. This report is not exhaustive and was performed for CNT surface modification exploration as it pertains to the "Next Gen" project.
Electrostatic modes of atomic force microscopy have shown to be non-destructive and relatively simple methods for imaging conductors embedded in insulating polymers. Here we use electrostatic force microscopy to image the dispersion of carbon nanotubes in a latex-based conductive composite, which brings forth features not observed in previously studied systems employing linear polymer films. A fixed-potential model of the probe-nanotube electrostatics is presented which in principle gives access to the conductive nanoparticle's depth and radius, and the polymer film dielectric constant. Comparing this model to the data results in nanotube depths that appear to be slightly above the film-air interface. This result suggests that water-mediated charge build-up at the film-air interface may be the source of electrostatic phase contrast in ambient conditions.
Increasing energy costs, the dependence on foreign oil supplies, and environmental concerns have emphasized the need to produce sustainable renewable fuels and chemicals. The strategy for producing next-generation biofuels must include efficient processes for biomass conversion to liquid fuels and the fuels must be compatible with current and future engines. Unfortunately, biofuel development generally takes place without any consideration of combustion characteristics, and combustion scientists typically measure biofuels properties without any feedback to the production design. We seek to optimize the fuel/engine system by bringing combustion performance, specifically for advanced next-generation engines, into the development of novel biosynthetic fuel pathways. Here we report an innovative coupling of combustion chemistry, from fundamentals to engine measurements, to the optimization of fuel production using metabolic engineering. We have established the necessary connections among the fundamental chemistry, engine science, and synthetic biology for fuel production, building a powerful framework for co-development of engines and biofuels.
The thermal cycling effects as well as isothermal conditions on a conductive multi-walled carbon nanotube (MWCNT) filled latex film are presented and analyzed for a multi-day exposure period. Using a water-based latex solution, multi-walled CNT's have been doped within it and then applied with stencil masked spray deposition to the surface of a non-conductive manufactured substrate. Four-point probe resistivity measurements were conducted in-situ via electrodes deposited across the width of the latex film on the top surface via brush application. The temperature range of consideration was computer controlled using a nitrogen purged environmental chamber cycling between-50 to 80 °C with isothermal holds at each extrema. We have identified long term and short-term temperature-dependent resistivity trends as well as a correlation between environmental conditions and the effect on electrical properties of the nanocomposite.
In this study we report a novel method of dispersing multi-walled carbon nanotubes (MWCNTs) using an electrospinning depositional process onto a conventional, uncured preimpregnated composite material. The main focus is the determination of the process parameters in order to consistently and homogeneously disperse MWCNTs onto a secondary substrate. Due to the exceptional thermal, mechanical, and electrical properties that can be exploited in CNTs, a homogenous dispersion can lead to isotropy in material properties of interest-mechanical, thermal, electrical etc. By combining these materials with structural composite materials, the true spirit of a tailored engineering material can be exploited even further to induce specific properties that are desired for a particular application. Through the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, as well as vertical scanning interferometry, the resulting electrospun fibers are imaged and correlated with process parameters.
This report summarizes the results of a one-year, feasibility-scale LDRD project that was conducted with the goal of developing new plastic scintillators capable of pulse shape discrimination (PSD) for neutron detection. Copolymers composed of matrix materials such as poly(methyl methacrylate) (PMMA) and blocks containing trans-stilbene (tSB) as the scintillator component were prepared and tested for gamma/neutron response. Block copolymer synthesis utilizing tSBMA proved unsuccessful so random copolymers containing up to 30% tSB were prepared. These copolymers were found to function as scintillators upon exposure to gamma radiation; however, they did not exhibit PSD when exposed to a neutron source. This project, while falling short of its ultimate goal, demonstrated the possible utility of single-component, undoped plastics as scintillators for applications that do not require PSD.