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Zhenpeng Li-Dissertation-Final.pdf (4.8 MB)

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Abstract Header

Information Programming by Scaling of Polymeric Layered Systems

Li, Zhenpeng
http://orcid.org/0000-0003-1495-8765
http://rave.ohiolink.edu/etdc/view?acc_num=case154834158541737

Abstract Details

2019, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science and Engineering.
Chapter 1: The shape memory behavior of polyvinyl acetate (PVAc), both at macro- and micro-scale, is presented. PVAc films exhibited excellent efficiency in programming macro-scale deformation. Cyclic tensile tests on PVAc films revealed the importance of molecular weight in programming macro-scale deformation in film. PVAc film with the highest molecular weight (~ 228 kDa) exhibited maximum durability in programming macro-scale deformation. This gives an important insight to the discovery of new shape memory polymers since chain entanglements in high molecular weight glassy polymers can impart shape memory behavior. In addition, such shape memory behavior can be exploited to imprint and tune micro-scale patterns on the film. Microprismatic patterns were embossed and programmed on shape memorizing PVAc films. Two different test methodologies were used to study the programmability of patterns on PVAc films. Pattern programming was significantly affected by the method used. In both cases, recovery time and temperature were two important parameters to determine the efficiency of programming. In addition, optical properties of PVAc films could be switched between reflective and transparent by programming patterns on the surface of the film. Chapter 2: Micro-scale surface shape memory effects were investigated on multilayer films that were produced with alternating layers of PVAc and PU. Two different types of micro-scale patterns, including a sharp microprismatic pattern and a smooth microlens pattern, were embossed on the surface of the PVAc/PU multilayer films by a PDMS replica mold using the soft lithography method. The microprismatic pattern as a permanent surface structure on the intrinsically transparent multilayer films renders the films opaque and the microlens surface pattern endows the clear films with focusing properties. The micro-structured surface is programmed by compression and recovery to switch the corresponding optical property of the film. Based on this switchable optical property, the patterned PVAc/PU multilayer film can be employed as an anti-counterfeiting feature in packaging. In this paper, the shape memory effect of the multilayered film was found to be dependent on the composition of the PVAc relative to the PU layers. In addition, the shape memory effect of the layered PVAc/PU films was enhanced compared to the PVAc control film. The recovery mechanism of the shape memory films was interpreted using Burgers viscoelastic model. The effects of the compression pressure, recovery temperature and the geometry of the patterns on the micro-scale shape memory behavior of the PVAc/PU multilayer films were also investigated. Chapter 3: Nano-layered films of PVAc/PU systems were fabricated by forced assembly coextrusion method. The bulk shape memory properties of PVAc/PU systems were utilized to program nanoscale patterns such as diffraction grating which exhibit iridescence after patterning. A hot embossing process has been utilized to imprint diffraction grating patterns as nano-scale information onto the surface of the thin multilayer films. Three levels of hierarchy i.e. layer thickness, spacing and heights of patterns, governs the functionality of the patterned multilayer film. The time and temperature dependent viscoelastic shape memory behavior determines the opto-mechanical tunability of the film. Mechanical switching of the patterns also leads to optical switching of the films which corresponds to their efficiency of information retrieval. The recovery of patterns as well as the diffractive property depends on the layer thickness (l) of films and heights of patterns (h0). The results illustrate that the higher ratio of h0/l better is the recovery of the grating patterns and the corresponding diffractive properties. This scaling effect enables versatile applications in information security by tuning the layer structure of the multilayer shape memory films. Chapter 4: The Polycarbonate (PC)/Nylon 6 and PC/Nylon 12 as well as PC/polyvinylidene fluoride (PVDF) 50/50 33L multilayer films were fabricated by forced assembly technology. The breakdown strengths, dielectric hysteresis properties and the broad band dielectric spectroscopic properties of these multilayer films were characterized as a function of temperature. At room temperature, the PC/Nylon 6 and PC/Nylon 12 films exhibited similar breakdown strengths as PC control films because of the small dielectric constant contrast between PC and Nylons. The PC/Nylon 6 and PC/Nylon 12 films exhibited a smaller energy density than PC/PVDF films at room temperature because of the smaller dielectric constants. At elevated temperatures higher than the Tgs of the Nylons (>75 ℃), PC/Nylon 6 and PC/Nylon 12 films presented enhanced breakdown strengths over PC control film, which were comparable with PC/PVDF films. The charge energy densities (Ucharge) of PC/Nylon 6 and PC/Nylon 12 films are higher than PC/PVDF film at temperatures higher than 100 ℃ because of the higher dielectric constants. The loss energy density (Uloss) of PC/Nylon 12 film is higher than the other two multilayer films because of a higher impurity ion mobility in Nylon 12 than Nylon 6 and PVDF. All in all, the discharge energy densities of PC/Nylon 6 and PC/Nylon 12 films are higher than PC/PVDF when the temperature increases over 100 ℃, which demonstrates that the PC/Nylon multilayer dielectric films are potential advanced capacitor films at high temperatures.
Eric Baer (Advisor)
Andrew Olah (Committee Member)
Lei Zhu (Committee Member)
James Anderson (Committee Member)
197 p.
Information Systems; Optics; Polymers
polymeric multilayer films; shape memory films; programmable optics; information programming; multilayer dielectrics; capacitor films

Recommended Citations

Citations

  • Li, Z. (2019). Information Programming by Scaling of Polymeric Layered Systems [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case154834158541737

    APA Style (7th edition)

  • Li, Zhenpeng. Information Programming by Scaling of Polymeric Layered Systems. 2019. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case154834158541737.

    MLA Style (8th edition)

  • Li, Zhenpeng. "Information Programming by Scaling of Polymeric Layered Systems." Doctoral dissertation, Case Western Reserve University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case154834158541737

    Chicago Manual of Style (17th edition)

case154834158541737
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© 2019, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.