Chemical and Biomolecular Engineering - Theses

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Start date: 1968 × Subject: convective polymer assembly × Subject: layer-by-layer × Subject: polymer capsules ×

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    Rapid, facile and automated polymer assembly techniques for the preparation of layer-by-layer capsules
    Richardson, Joseph Jacob ( 2014)
    Layer-by-layer (LbL) assembled films and capsules have shown potential application in diverse fields such as energy and drug delivery, because they can be prepared from various polymers and loaded with numerous materials. Although film deposition on planar substrates can be rapid and facile using techniques such as spray-coating or spin-coating, the layering of particles generally requires longer and more involved protocols. LbL assembly on particles typically uses random diffusion as the adsorption driving force, which can lead to the risk of aggregation during layering and washing. To overcome the inherent challenges surrounding polymer deposition on particulate matter, immobilization techniques for suspending the template particles were developed. Immobilizing the template particles has allowed for rapid, facile, and automated layering methods to be applied to particles of varying sizes and compositions. Large particles were suspended in a liquid-based fluidized bed for layering, while smaller particles required immobilization in a porous hydrogel before facile layering was possible. The use of a fluidized bed allowed for the large scale production of polymer microcapsules at a rate roughly ten times faster than conventional methods. However, this technique was generally limited to particles above 5 micrometers. For the hydrogel immobilized particles, a naturally derived polysaccharide, agarose, was used as an immobilizing agent. Electrophoresis, convection and diffusion were then used to deposit polymers on immobilized particles and form capsules ranging from below 100 nanometers to above 1 micrometer. These driving forces allow for the use of different polymer combinations, can be used to load various types of cargo, and can be used to form polymer replica particles. Each driving force has unique benefits, and all three driving forces are either already automated, or potentially automatable. The speed, ease, scope and scale with which these capsules can now be produced should benefit research and development directed towards the application of LbL capsules.