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Ellipsometry Measurements of Chemical Reactions and Diffusion Processes in Polymer films

Lin, Kehua
http://rave.ohiolink.edu/etdc/view?acc_num=akron1468703681

Abstract Details

2016, Master of Science in Polymer Engineering, University of Akron, Polymer Engineering.
Chemical crosslinking of layer-by-layer assembled films promotes mechanical stability and robustness in a wide variety of environments, which can be a challenge for polyelectrolyte multilayers in saline environments or for multilayers made from weak polyelectrolytes in environments of pH extremes. Heating branched poly(ethylene imine)/poly(acrylic acid) (BPEI/PAA) multilayers at sufficiently high temperature drives amidization and dehydration to covalently crosslink the film, but this reaction is rather slow with hours of heating typically required for appreciable crosslinking to occur. Here, more than an order of magnitude increase in the amidization kinetics is realized through microwave heating of BPEI/PAA multilayers on ITO/glass substrates. The crosslinking reaction is tracked using infrared spectroscopic ellipsometry to monitor the development of the crosslinking products. For thin films (c.a. 500 nm), microwave crosslinking generates a more uniform network as determined by ion diffusion during electrochemical impedance spectroscopy than does conventional heating, and for thick films (c.a. 1500 nm), gradients in the crosslink density can be readily identified by infrared ellipsometry. Such gradients in crosslink density are driven by the temperature gradient developed by the localized heating of ITO by microwaves. This significant acceleration of reactions using microwaves to generate a homogeneous crosslink network as well as being a simple method to develop graded materials should open new applications for these polymer films and coatings. As the infrared ellipsometry can detect the graded extinction coefficient which due to the graded crosslink density, IR ellipsometry can also use to measure the inter diffusion between different polymers. In this study, a new model using graded extinction coefficient through the bilayer system is introduced. Polymers used in this study are two types of polycarbonates (PC), which is a versatile material, have many applications in different aspect. Those two types of PC have different Tg. This material have several good properties such as high impact, temperature resistance, transparency and good electrical insulation properties. Several theory have tried to explain diffusion. However those theory are not perfect. Ellipsometry is an excellent way to observe the diffusion because it is a non-contact and non-destructive measurement. Form the result obtained, an obvious interfacial film broadening can be observed. When the heating temperature is higher than Tg of both polymers, both polymers exhibit high mobility. Moreover, when the heating temperature Tg1 < T < Tg2 (1 and 2 represent two different PC respectively, specific material are introduced in Chapter III), PC-1 shows a much higher mobility than PC-2. The interface broadening are most contributed by PC-1 as it moves much faster than PC-2.
Bryan Vogt (Advisor)
Nicole Zacharia (Committee Chair)
Steven Chuang (Committee Member)
81 p.
Polymers

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Citations

  • Lin, K. (2016). Ellipsometry Measurements of Chemical Reactions and Diffusion Processes in Polymer films [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468703681

    APA Style (7th edition)

  • Lin, Kehua. Ellipsometry Measurements of Chemical Reactions and Diffusion Processes in Polymer films. 2016. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1468703681.

    MLA Style (8th edition)

  • Lin, Kehua. "Ellipsometry Measurements of Chemical Reactions and Diffusion Processes in Polymer films." Master's thesis, University of Akron, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468703681

    Chicago Manual of Style (17th edition)

akron1468703681
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This open access ETD is published by University of Akron and OhioLINK.