"Aerogels are open-cell nanoporous materials, unique in terms of low density, low thermal conductivity, low dielectric constants and high acoustic attenuation. Those exceptional properties stem from their complex hierarchical solid framework (agglomerates of porous, fractal secondary nanoparticles), but they also come at a cost: low mechanical strength. This issue has been resolved by crosslinking silica aerogels with organic polymers. The crosslinking polymer has been assumed to form a conformal coating on the surface of the skeletal framework by covalent bridging elementary building blocks. However, "assuming" is not enough: for correlating nanostructure with bulk material properties, it is important to know the exact location of the polymer on the aerogel backbone. For that investigation, we synthesized a new norbornene derivative of triethoxysilane (Si-NAD) that can be attached to skeletal silica nanoparticles. Those norbornene-modified silica aerogels were crosslinked with polynorbornene by ring opening metathesis polymerization (ROMP). The detailed correlation between nanostructure and mechanical strength was probed with a wide array of characterization methods ranging from molecular to bulk through nano. Subsequently, it was reasoned that since the polymer dominates the exceptional mechanical properties of polymer crosslinked aerogels, purely organic aerogels with the same nanostructure and interparticle connectivity should behave similarly. That was explored and confirmed by: (a) synthesis of a difunctional nadimide monomer (bis-NAD), and preparation of robust polyimide aerogels by ROMP of its norbornene end-caps; and, (b) synthesis of dimensionally stable ROMP-derived polydicyclopentadiene aerogels by grafting the nanostructure with polymethylmethacrylate (PMMA) via free radical chemistry"--Abstract, page iv.
Whitefield, Philip D.
Ph. D. in Chemistry
United States. Army Research Office
National Science Foundation (U.S.)
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Monolithic hierarchical fractal assemblies of silica nanoparticles crosslinked with polynorbornene via ROMP: a structure-property correlation from molecular to bulk through nano
- Polyimide aerogels by ring opening metathesis polymerization (ROMP)
- Nanotopology of bulk deformation in polydicyclopentadience gels, and how grafting with PMMA yields dimensionally stable nanoporous solids (Aerogels
xvi, 227 pages
© 2012 Dhairyashil P. Mohite, All rights reserved.
Dissertation - Open Access
Small-angle x-ray scattering
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Electronic OCLC #
Link to Catalog Record
Mohite, Dhairyashil, "Organic and composite aerogels through ring opening metathesis polymerization (ROMP)" (2012). Doctoral Dissertations. 1972.