A REVIEW AND STUDY OF VERY HIGH NANOFILLER-CONTENT NANOCOMPOSITES: THEIR PREPARATION METHODS, CHARACTERIZATION AND PROPERTIES by JEFFREY PHILIP GEORGE Submitted for partial fulfillment of the requirements For the degree of Master of Science Thesis adviser: Dr. Hatsuo Ishida Department of Macromolecular Science and Engineering CASE WESTERN RESERVE UNIVERSITY August, 2019 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis/dissertation of Jeffrey Philip George candidate for the degree of Master of Science*. Committee Chair Dr. Hatsuo Ishida Committee Member Dr. David Schiraldi Committee Member Dr. Gary Wnek Date of Defense June 6th, 2019 *We also certify that written approval has been obtained for any proprietary material contained therein. Table of Contents Table of Contents................................................................................................ i List of Figures..................................................................................................... iv List of Tables...................................................................................................... x Acknowledgement.............................................................................................. xi Abstract............................................................................................................... xii Chapter 1: A Review on the Very High Nanofiller-Content Nanocomposites: Their Preparation Methods and Properties with High Aspect Ratio Filler........ 1 1.1 Introduction............................................................................................... 2 1.2 Definition of Nanofillers........................................................................... 4 1.3 Types of Nanofillers.................................................................................. 6 1.3.1 Clay Nanofiller................................................................................. 6 1.3.2 Graphene Oxide Nanofiller.............................................................. 8 1.3.3 Other Nanofillers.............................................................................. 9 1.4 Different Fabrication Techniques.............................................................. 9 1.4.1 Layer-by-Layer Deposition Techniques and Its Variants................. 10 1.4.2 Electrophoretic Deposition (EPD) ................................................... 14 1.4.3 Mechanical Self-assembly Methods................................................. 15 1.4.3.1 Earlier Mechanical Methods....................................................... 16 1.4.3.2 Doctor Blading (DB) and Vacuum Assisted Filtration (VAF)... 17 1.4.3.3 Solution Casting (SC)…............................................................. 21 1.4.3.4 Gel Casting and Hot-pressing Fabrication Method.................... 25 1.4.4 Other Novel Techniques................................................................... 26 1.4.4.1 Chemical Assembly.................................................................... 26 1.4.4.2 Gel-film Transformation Method............................................... 29 1.4.4.3 Ice Templating............................................................................ 30 1.4.4.4 Freeze Drying............................................................................. 31 1.4.4.5 Wet Spinning.............................................................................. 33 1.4.4.6 Other Methods for Viscous Systems.......................................... 34 1.4.5 Fabrication of Single Component Nanocomposite Systems............ 36 1.5 Surface Modification................................................................................. 37 i 1.5.1 Surface Treatment of Polymer......................................................... 37 1.5.2 Chemical Treatments of Inorganic Nanofillers................................ 39 1.5.3 Grafting Modification of Nanoparticles........................................... 42 1.6 Mechanical Properties of High Filler-content Nanocomposites............... 46 1.6.1 Effects of Interfacial Interactions..................................................... 46 1.6.1.1 Hydrogen Bonding..................................................................... 47 1.6.1.2 Covalent Bonding....................................................................... 50 1.6.1.3 Electrostatic Bonding................................................................. 51 1.6.1.4 Synergistic Combinations of Bonding....................................... 54 1.6.2 Effects of Crosslinking Agents........................................................ 59 1.6.3 Effects of Fabrication Methods........................................................ 65 1.6.4 Effects of Electrochemical Reduction.............................................. 67 1.7 Electrical Properties of High Filler-content Nanocomposites................... 71 1.8 Gas Barrier Properties of High Filler-content Nanocomposites................ 75 1.9 Flame Retardancy Properties of High Filler-content Nanocomposites...... 78 1.10 Conclusions................................................................................................ 81 Chapter 2: Application of Very High Nanofiller-content Laponite/DNA Nanocomposite coating on Polyurethane Foam through Single-Dip Fabrication 83 2.1 Introduction................................................................................................. 84 2.2 Experimental Section.................................................................................. 87 2.2.1 Materials............................................................................................ 87 2.2.2 Preparation of LAP/DNA suspensions.............................................. 87 2.2.3 Preparation of coated PU foams......................................................... 88 2.2.4 Preparation of LAP/DNA nanocomposite films................................ 88 2.2.5 Characterization................................................................................. 88 2.3 Results and Discussion................................................................................ 89 2.3.6 FT-IR spectroscopy............................................................................ 89 2.3.7 SEM and EDX analysis...................................................................... 91 2.3.8 Thermal Stability................................................................................ 92 2.3.9 Compression Testing.......................................................................... 95 2.3.10 Flammability...................................................................................... 97 ii 2.4 Conclusion.................................................................................................. 99 2.5 Acknowledgement...................................................................................... 99 References........................................................................................................... 100 iii List of Figures 1. Figure 1.1: Geometric definition of nanofillers. (a) nanoparticle, (b) nanorod, (c) nanoplatelet, (d-f) secondary particle or aggregate form of each nano-fillers...................................................................................... 4 2. Figure 1.2: Proposed structural models of MTM/PVA nanocomposites prepared by evaporation-induced assembly. (a) The composites with MTM weight fraction, w, between 0 wt% and 30 wt% have a random structure. The crystallinity of PVA decreases, accompanied by the increase of the constrained region. (b) The composites with w between 30 wt% and 70 wt% have a nacre-like layered structure. PVA is completely constrained by MTM platelets. (c) The structure of composites with w between 70 wt% and 100 wt% is transformed to tactoids..................... 5 3. Figure 1.3: The structure of a 2:1 layered silica.................................... 8 4. Figure 1.4: The structural model of Graphene oxide............................. 8 5. Figure 1.5: (A) Schematic diagram of a LbL assembly method. (B) Simplified picture of alternating layers of oppositely charged polymers being adsorbed on substrate. (C) Chemical structures of sodium salt of poly(styrene sulfonate) and poly(allylamine hydrochloride)................. 11 6. Figure 1.6: Free-standing, 300-bilayer PVA/MTM composite film showing high flexibility and transparency............................................. 12 7. Figure 1.7: The SA-LbL fabrication of CH/AL nanocomposite films... 13 8. Figure 1.8: The scheme showing the electrophoretic deposition assembly to construct nano-laminated film structure............................................. 15 9. Figure 1.9: Schematic illustrations of the different physical methods used to increase the orientation of the talc tablets.......................................... 17 10. Figure 1.10: A schematic representation of the VAF fabrication of nano- composite films from a solution of dispersed inorganic nanofiller and polymer.................................................................................................. 18 11. Figure 1.11: SEM and TEM images of various layered PVA/MTM nacre- mimetic paper composites obtained via paper-making process. Panels a-d show films of thicknesses of 0.17, 0.063, 0.044, and 0.026mm, iv demonstrating that even thick films can be prepared and the film thickness can be tuned. The digital photograph (e) demonstrates the light translucence of nacre-mimetic papers of various thicknesses (from left