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PROBING POLYMER DYNAMICS USING HIGH THROUGHPUT BROADBAND DIELECTRIC SPECTROSCOPY

Xiao, Zhang
http://rave.ohiolink.edu/etdc/view?acc_num=akron1533127319642101

Abstract Details

2018, Doctor of Philosophy, University of Akron, Polymer Engineering.
The non-Arrehnius behaviors of glass transition dynamics have attracted a great deal of research efforts. Despite challenges, several key parameters have been identified, including glass transition temperature, fragility, and the stretching exponent ß. A deeper understanding of the dynamic correlations among these parameters is useful for discovering new theories and developing next-generation materials. Besides the dynamic correlations, it is worthwhile to investigate the tunability of these parameters. A systematic investigation of these underlying connections requires screening a large number of samples, which poses a great challenge for the traditional BDS setup. The goals of this dissertation are, thus, to: 1) develop a high-throughput experimental setup for BDS; 2) further investigate the underlying connections among Tg, m, and the stretching exponent ß; and 3) investigate the tunability of Tg and m through copolymerization and nanoparticles. In the first part of our research, we have successfully developed High Throughput Broadband Dielectric Spectroscopy (HTBDS), a novel strategy to probe dynamics of a large number of samples within a short amount of time. The results agree well with the commercially available BDS setup. In this section, the overall setup of testbed, temperature control, structure of the LabView program, and operation protocols have been discussed. Following these developed protocols, we used three polymers as test materials to validate the instrument. The results are in agreement with results from the commercially available setup. Consequently, the HTBDS setup realizes an order of magnitude improvement of experimental throughput. Upon validating the HTBDS instrument, in the second part of this research, we applied this new strategy to probe a series of acrylate-based statistical copolymers. Tg, m, and the stretching exponent ß, and the underlying dynamical correlations have been investigated. The results on T_g agree with the Fox glass transition mixing rule based on the bulk mass concentration, indicating the absence of self-concentration effects observed from other systems. In terms of m, we found that fragilities at 100 s show nonmonotonic trends with comonomer compositions. Its values extrapolated at 0.001 s exhibit a roughly linear correlation with monomer concentrations. As of dynamical correlations, the stretching exponent ß is correlated roughly with T_g, but not with fragility. In the third part of research, we attempt to conduct a combinatorial study on the effect of additives on the polymer glass transition dynamics. First, we found that dispersion alone does not guarantee the changes of polymer dynamics, as evidenced by the results found in the PCL/surfactant-free clay systems. The dispersion level was confirmed by scattering and microscopic analysis, and the BDS results This corroborates the previous simulation efforts suggesting that such parameters as particle sizes, interfacial energy, and matrix-additive stiffness contrast play vital roles for Tg and m. Therefore, we used HTBDS to further investigate a series of polymer-nanoparticle systems with varying molecular structures for both the particles and the matrices. We have identified polymer-particle systems exhibiting both trivial and non-trivial interfacial confinement effects. Different levels of the interfacial confinement effect were employed to test the robustness of two different functional forms.
David S. Simmons (Advisor)
Alamgir Karim (Advisor)
Kevin Cavicchi (Committee Chair)
Yu Zhu (Committee Member)
Siamak Farhad (Committee Member)
147 p.
Chemical Engineering; Chemistry; Polymer Chemistry; Polymers
Polymer Dynamics; Interfacial Confinement; Polymer Glass Transition; Polymer Nanocomposites; Dielectric Spectroscopy; High Throughput Characterization

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Citations

  • Xiao, Z. (2018). PROBING POLYMER DYNAMICS USING HIGH THROUGHPUT BROADBAND DIELECTRIC SPECTROSCOPY [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1533127319642101

    APA Style (7th edition)

  • Xiao, Zhang. PROBING POLYMER DYNAMICS USING HIGH THROUGHPUT BROADBAND DIELECTRIC SPECTROSCOPY . 2018. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1533127319642101.

    MLA Style (8th edition)

  • Xiao, Zhang. "PROBING POLYMER DYNAMICS USING HIGH THROUGHPUT BROADBAND DIELECTRIC SPECTROSCOPY ." Doctoral dissertation, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1533127319642101

    Chicago Manual of Style (17th edition)

akron1533127319642101
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This open access ETD is published by University of Akron and OhioLINK.