Keywords and Phrases
Aerogels; Contact angle; K-index; Morphology; Polyurea; SEM
"The morphology of a material is intrinsically a qualitative property and in order to relate nanomorphology to synthetic conditions, it is necessary to express nano/micro-structure quantitatively. In this context, polyurea aerogels were chosen as a model system with demonstrated potential for rich nanomorphology and being guided by a statistical Design-of-Experiments model, a large array of materials (208) with identical chemical composition, but quite different nanostructures were prepared. By reflecting upon the SEM images, it was realized that our first pre-verbal impression about a nanostructure is related to its openness and texture; the former is quantified by porosity (Π), and the latter is related to the contact angle (θ) of water droplets resting on the material. Herewith, the θ/Π ratio is referred to as the K-index, and it was noticed that all polyurea aerogel samples could be put in eight K-index groups with separate nanomorphologies. The K-index was validated as a morphology predictor by compressing samples to different strains: as porosity decreases, contact angle decreases proportionally, and the K-index remains constant. The predictive power of the K-index was demonstrated with new PUAs prepared in eight binary solvents. Finally, using response surface methodology, K-indexes and other material properties of interest were correlated to synthetic conditions, thus enabling synthesis of materials with prescribed properties at a time. The second part of this dissertation focuses on polyurea aerogels consisting of different arrangements of nanoparticles (1.2 ≤ K-index ≤ 1.5). SAXS, XRD and SEM have demonstrated that these nanostructures consist of similar-size primary particles. A model for the formation of these nanoparticles through Molecular Dynamic simulations is suggested"--Abstract, page iv.
Miller, F. Scott, 1956-
Ph. D. in Chemistry
National Science Foundation (U.S.)
United States.Army Research Office
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- K-index: A descriptor, predictor and correlator of complex nanomorphology to other material properties
- Multi-scale progressive failure mechanism and mechanical properties of nanofibrous polyurea aerogels
xiii, 242 pages
© 2019 Tahereh Taghvaee, All rights reserved.
Dissertation - Open Access
Electronic OCLC #
Taghvaee, Tahereh, "Polyurea aerogels: From nanoscopic to macroscopic properties" (2019). Doctoral Dissertations. 2813.