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http://hdl.handle.net/11375/28347
Title: | Flexible Nanoscale Composites with Co-Continuous Morphology Prepared by Controlled Cavitation of Thermoplastic Materials and In Situ Polymerization of Conductive Networks |
Authors: | Kornberg, Anton |
Advisor: | Zhu, Shiping Thompson, Michael |
Department: | Chemical Engineering |
Keywords: | co-continuous structures, composite materials, conductive polymers, organic electronics, flexible electronics, battery materials, interfaces |
Publication Date: | 2022 |
Abstract: | For the purpose of creating inexpensive micro- and nano-scaled network structures of ion- or electron-conductive nature without significant deterioration to the inherent mechanical nature of a commodity thermoplastic or elastomer, a novel investigation was undertaken to use controlled cavitation in the matrix of a commodity polymer. To thoroughly examine the capabilities of this approach with cavitation, the initial morphology of the matrix was varied based on the distribution and structure of its crystalline phase. This action of significant cavitation intensification created a void space within which a secondary polymer network of unique functionality could be introduced. The preliminary experiments showed that the approach under exploration was able to incorporate a continuous ion-conductive network into a polyethylene matrix, with remarkably minor losses in its mechanical properties despite the soft gel-like nature of the new polymer phase. Control over the resulting matrix morphology was gained by varying experimental conditions, such as applied pressure and degree of matrix elongation. The frequency of interface defects, on which transverse crazes were initiated, was increased by expanding the crystal-amorphous boundary area. The reactive polymerization solution, while penetrating the matrix, lowered the energy of the inner surface of the emerging crazes, thereby influencing the channels by which it penetrated. Upon polymerization and soaking with an electrolyte, a continuous conductive acrylic hydrogel now formed an internal network in the polyethylene specimen. The resulting material displayed ion conductivity approaching that of the pure acrylic hydrogel while its modulus declined by only 12%. The continued experiments examined the creation of a continuous nanoscaled network in an olefinic matrix to impart it with higher value-added functionality, in that case, potentially combined ion and electron conductivity. Such structures were fabricated based on the same procedure in a high-pressure reactor by stretching polyethylene films while immersing them in an emulsified medium of aniline in chloroform, which resulted in the formation of crazes filled with doped polyaniline. The important element to these experiments was the pre-compounded addition of synthesized polyaniline fibers as a nucleating agent in the polyethylene matrix, which reduced the size of its crystallites and subsequently enhanced the material conductivity by acting as nodes to the emerging polyaniline network synthesized withing the deformation-induced crazing. Excessively high craze frequency was not desirable since it resulted in a decrease in the craze diameter, making it difficult for the polyaniline emulsion droplets to penetrate the matrix. The final part of the work was focused on alternative matrix materials, such as polyolefin elastomers (POE), which could increase the flexibility of a resulting conductive materials. The experiments aimed at studying the effect of initial domain structure on cavitation behavior with three different POEs and, accordingly, characterize their resulting conductivity. Successful materials were demonstrated, though only after overcoming their excessive elastic recovering which would otherwise collapse the craze voids before the secondary polymer phase could permanently established itself as a conductive network. The results presented in this study demonstrate the capability of controlled crazing through morphological tuning to create inexpensive materials for battery and flexible electronics manufacturing, where conductive polymer composites are widely adopted. |
URI: | http://hdl.handle.net/11375/28347 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Kornberg_Anton_B_2022-12_PhD.pdf | 15.3 MB | Adobe PDF | View/Open |
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