One-Step Coassembly of Nacre- Like Polymer Nanocomposites and Effects of Processing Methods

Organic/inorganic hybrid nanocomposite coatings (nanocoatings) with a nacre-like structure have been of great interest across many industries because of their outstanding properties. There are many processing methods that have been developed to create nacre-like materials, especially nacre-like coatings. However, many of these proposed methods present issues with scalability, involving complex processing steps, long processing times, harsh or harmful reagents, or limits to sample size. Any modern technology, especially for widespread consumer applications such as food packaging or wearable electronics, should be produced using scalable, environmentally-friendly means.
In this dissertation, we explore a flow-based method of producing nanocomposite materials with well-oriented nanosheets for various applications. I explore numerous approaches to improving flow-induced assembly, including materials selection, interface engineering, and processing technique. Dip coating, for example, is a scalable, versatile method of producing thin nanocomposite films. Using polyvinyl alcohol (PVA) is a binder material and exfoliated montmorillonite (MMT) clay as a filler material across these projects, I present the ways in which the choice of substrate, the use of additional filler materials, the molecular weight and degree of hydrolysis of PVA, and the degree of filler loading affect the properties (such as oxygen and water vapor barrier properties) of formed dip-coated films.
While dip-coating has proved to be an ideal approach to fabricating thin films, the fundamentals of the coassembly process need to be investigated for other processing techniques. Doctor blade coating and spin coating are two approaches in which hydrodynamic shear and high particle acceleration can induce high alignment of nanosheets. In doctor blade-assisted casting, the shearing force provided by the blade helps to induce high nanosheet alignment in the nanocoatings. Certain film properties, such as barrier performance, are able to be controlled via processing parameters, such as blade speed and suspension concentration. Spin coating uses centripetal acceleration to align the nanosheets into a similar nacre-like structure with little to no radial dependence on film thickness. Both methods were shown to create nanocoatings with sufficient barrier performance for various applications.