Doctoral Dissertations

Keywords and Phrases

Aerogels; Contact angle; K-index; Morphology; Polyurea; SEM

Abstract

"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.

Advisor(s)

Leventis, Nicholas

Committee Member(s)

Sotiriou-Leventis, Lia
Choudhury, Amitava
Nath, Manashi
Miller, F. Scott, 1956-

Department(s)

Chemistry

Degree Name

Ph. D. in Chemistry

Sponsor(s)

National Science Foundation (U.S.)
United States.Army Research Office

Comments

Financial support for this study was provided by National Science Foundation under Award No. CMMI-1030399 and the ARO under Award No. W911NF-14-1-0369.

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2019

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

Pagination

xiii, 242 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2019 Tahereh Taghvaee, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11604

Electronic OCLC #

1119724207

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