Polyelectrolyte nanocapsules: continuous fabrication of multipurpose containment materials
File(s)
Author(s)
Elizarova, Iuliia
Type
Thesis
Abstract
The layer-by-layer approach is a highly versatile technique for fabrication of multi-layered structures of various shapes by consecutive deposition of oppositely charged materials (polyelectrolytes) onto selected substrates. This technique allows for control over size, shape, composition and thickness of the fabricated films. One of the main applications of this technique is the preparation of loadable multi-layered capsules that can be used in a variety of fields including drug delivery, self-healing materials, wastewater treatment, and others. The widely used classic layer-by-layer procedure for preparation of such capsules involves mixing of substrate particles with a saturated polyelectrolyte solution, waiting for the polyelectrolyte to adsorb onto the particles, and removing excess polyelectrolyte from the system by washing. This procedure has to be repeatedly performed for each successive layer. This leads to long production times, high labour intensity and significant losses of both construction and produced materials. This thesis addresses the aforementioned issues and describes the design and execution of the advanced flow-based capsule fabrication technique termed "continuous layer-by-layer approach" capable of producing hundreds of milligrams of multi-layered capsules per hour. Polyelectrolyte multi-layering occurs in tubing where templates are mixed with polyelectrolyte solution of choice resulting in the formation of polyelectrolyte layer around them. Newly coated templates are then passed into the next tubing segment to be mixed with a second polyelectrolyte solution of the opposite charge. This procedure can be repeated continuously until the desired number of layers is achieved. The main principle behind this method, which allows for elimination of intermediate washing steps, is using just enough polyelectrolyte to ensure the fabrication of a stable layer around templates while keeping the amount of unadsorbed polyelectrolyte present in the solution to a minimum. The developed method has been successfully used for fabrication of several types of hollow nano-capsules and functional multi-layered emulsions.
Version
Open Access
Date Issued
2017-10
Date Awarded
2018-02
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
License URL
Advisor
Luckham, Paul
Sponsor
Imperial College London
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)