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Title: Fabrication of polymeric microcarriers with reduced permeability using layer-by-layer, surface-initiated polymerization and emulsion techniques
Author: Zhao, Li
ISNI:       0000 0004 7652 7247
Awarding Body: Queen Mary University of London
Current Institution: Queen Mary, University of London
Date of Award: 2017
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In recent years, polymeric microcarriers have drawn great attention because of their potential applications in medical, cosmetic and some other industries. A variety of materials, preparation techniques have been explored to endow these microcarriers the desired properties. In spite of encouraging improvements in other properties, the low permeability of microcarriers remains a challenge which results in massive amount of cargo loss due to fast release. This work aimed to develop microcarriers with reduced permeability by coating with biocompatible and hydrophobic polymers via different techniques such as Layer-by-Layer, surface-initiated atom transfer radical polymerization and emulsion methods. This thesis starts with an introduction and literature review, which present the background of this work, followed by the description of materials as well as methods used in this work in chapter 3. Chapter 4 studied various parameters for fabricating structurally intact Poly(lactic acid) stereocomplex microcapsules, and demonstrated that heat treatment could significantly reduce the permeability of PLA microcapsules. In chapter 5, Layer-by-Layer and surface-initiated atom transfer radical polymerization techniques were combined to fabricate PMMA coated microparticles with low permeability. A polyelectrolyte macroinitiator and Poly(sodium 4-styrenesulfonate) were first deposited onto CaCO3 particles through LbL process, followed by growing PMMA brush layer via ATRP from the polyelectrolyte precursor. Chapter 6 introduced a simple emulsion method to prepare PLA coated CaCO3 microparticles with low permeability, which can retain bioactive molecules within the particles. It was found that 0.8 was the optimal CaCO3/PLA mass ratio in terms of the low permeability of microparticles as well as high-usage of polymers. In chapter 7, PLA films were synthesized from two different types of macroinitiators, with one being polyelectrolyte based and the other one being Poly(2-hydroxyethyl methacrylate) polymer brush precursor. The kinetics of PLA film growth from different precursors was compared whilst degradation of PLA films was also studied.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Engineering and Materials Science ; Polymerization ; polymeric microcarriers