Determining the role of charges in ionic polymer blend systems

Huang, Jennifer

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https://hdl.handle.net/2142/102851 Copy

Description

Title

Determining the role of charges in ionic polymer blend systems

Author(s)

Huang, Jennifer

Issue Date

2018-12-10

Director of Research (if dissertation) or Advisor (if thesis)

Evans, Christopher

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

ionic polymer blends, miscibility, crystalline, kinetics, amorphous, conductivity

Abstract

Little is known experimentally about the effect of charge in ionic multi-polymeric systems. Theory has shown that many charged systems have unusual phase diagrams that are asymmetric. Such a phenomenon would be ideal for tuning domain sizes or obtaining nontraditional structures in materials. One of the two studies presented in this thesis focuses on the crystallization kinetics in a crystalline-crystalline polymer blend, to better understand how to tune the number density and size of crystalline domains in crystalline-crystalline and crystalline-amorphous polymer blends. The blend system’s miscibility, kinetics, and final structures were studied at different compositions and compared to the homopolymers via differential scanning calorimetry (DSC), polarized optical microscopy (POM) and grazing-incidence wide-angle x-ray scattering (GI-WAXS). From DSC, the blends were found to melt at the same temperatures as the homopolymers but crystallize at much lower temperatures (at least a 20°C shift) due to slower kinetics. The blend kinetics were studied quantitatively via POM spherulite measurements over time and agreed with DSC data. GI-WAXS showed that the blends displayed crystalline features from both the individual components. The second study presented in this thesis focuses on amorphous charged blends. The blends are comprised of a plus-neutral polymer for high ionic selectivity, and poly(2-vinylpyridine) (P2VP) for mechanic integrity. Under proper processing conditions, the blend system was found to be at least partially miscible from being visually transparent and from having observed shifts of two glass transition temperatures inwards from those of the individual homopolymers. Preliminary conductivity data showed a decrease of at least four orders of magnitude when 50 wt% P2VP was added. For membrane applications, the trade-off between good mechanical properties and high ionic selectivity is yet to be optimized.

Graduation Semester

2018-12

Type of Resource

text

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http://hdl.handle.net/2142/102851

Copyright and License Information

Copyright 2018 Jennifer Huang

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