Doctoral Dissertations
Abstract
"Aerogels are porous lightweight materials, unique among all solids in terms of low density, low thermal conductivity, low dielectric constants and high acoustic attenuation. The penalty for those exceptional properties is fragility. That issue has been addressed by bridging covalently (crosslinking) the elementary nanoscopic building blocks of silica aerogels with polymers. To streamline the crosslinking process we synthesized a bidentate free radical initiator (Si-AIBN) that gets attached on the skeletal nanoparticles and induces crosslinking by surface initiated polymerization (SIP). Here, we extend the scope of Si-AIBN in two directions: (a) we demonstrate extremely adhering, covalently attached polymer coatings on oxidized surfaces (glass, metal) and eventually we adapt the method into highly durable conducting polymer films; and, (b) we engage a carbonizable crosslinker (acrylonitrile), whereas the resulting polymer coating, polyacrylonitrile (PAN), can react carbothermally with the underlying silica backbone to yield monolithic, highly porous (>70% v/v) silicon carbide (SiC) suitable as a high temperature catalyst support. Meanwhile, PAN is the major starting material of carbon fiber used industrially in high-strength composites for automotive and aerospace applications. It was thus deemed desirable to explore the synthesis of PAN-derived porous carbons. Although free-radical solution polymerization of acrylonitrile may afford gels, those linear-polymer based gels collapse upon drying and they cannot be converted to aerogels. Use of 1,6-hexanediol diacrylate (HDDA) or ethyleneglycol dimethacrylate (EGDMA) as molecular crosslinkers induces phase-separation of "live" nanoparticles that react with one another forming a robust, covalently bonded 3D network than can be dried into carbonizable and eventually graphitizable aerogels. Phase-separation can be also induced prior to polymerization by surfactants, and thus eventually we demonstrate an environmentally friendly aqueous route to PAN aerogels and carbons"--Abstract, page iv.
Advisor(s)
Sotiriou-Leventis, Lia
Leventis, Nicholas
Committee Member(s)
Nath, Manashi
Whitefield, Philip D.
Kakkatukuzhy, Isaac M.
Department(s)
Chemistry
Degree Name
Ph. D. in Chemistry
Publisher
Missouri University of Science and Technology
Publication Date
Summer 2011
Journal article titles appearing in thesis/dissertation
- Robust PEDOT films by covalent bonding to substrates using in tandem sol-gel, surface initiated free-radical and redox polymerization
- Click synthesis of monolithic silicon carbide aerogels from polyacrylonitrile-coated 3D silica networks
- "Green" aerogels and porous carbons by emulsion gelation of acrylonitrile
Pagination
xv, 170 pages
Note about bibliography
Includes bibliographical references.
Rights
© 2011 Anand G. Sadekar, All rights reserved.
Document Type
Dissertation - Open Access
File Type
text
Language
English
Subject Headings
Aerogels
Colloids
Free radicals (Chemistry)
Nanotechnology
Thesis Number
T 9904
Print OCLC #
795201803
Electronic OCLC #
795395111
Link to Catalog Record
Recommended Citation
Sadekar, Anand G., "Aerogels and films through free radical polymerization" (2011). Doctoral Dissertations. 2125.
https://scholarsmine.mst.edu/doctoral_dissertations/2125