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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
Research Student Awards

PhD Thesis: Processing of Polymer-based Systems for Improved Performance and Controlled Release

Author: MA, Jia

Year: 2011

Supervisor(s): Gleb Sukhorukov, Ton Peijs

This thesis focuses on improved processing methods for enhanced mechanical
properties in polymer nanocomposites, and controlled drug release in polymer based
delivery systems. Supercritical carbon dioxide assisted mixing was successfully used
in preparation of polypropylene/sepiolite and polypropylene/multiwall carbon
nanotube nanocomposites. Relatively homogeneous dispersed and well separated
nanofillers were obtained throughout the PP matrix. A better preservation of
nanofiller lengths was observed in the scCO2 assisted mixing. Mechanical property
studies showed a marked increase in Young’s modulus and tensile strength with the
addition of nanofillers. More interestingly, techniques usually designed to achieve
high quality PP nanocomposites, such as the use of masterbatches, maleic anhydride
grafted polypropylene compatibilizers or polymer coated MWNTs are not needed to
achieve equivalent mechanical properties with scCO2 assisted mixing. ScCO2 was
also used as a foaming technique to modify the traditional cured poly(ethyl
methacrylate/tetrahydrofurfuryl methacrylate) system for a controlled release of
chlorhexidine. Highly porous structures were produced and chlorhexidine released
from scCO2 foamed samples was more than 3 times higher than traditionally cured
samples. By altering the processing conditions, such as CO2 saturation time and
depressurization time the CX release rate was altered. Finally, the electrospinning
method was combined with the layering encapsulation technique in order to enable
the incorporation of water-soluble drugs in poly(lactic-co-glycolic acid) fibres for
biomedical applications. Water-soluble drug, Rhodamine 6G or protein bovine serum
albumin, loaded calcium carbonate microparticles were successfully incorporated in
PLGA fibres and a bead and string structured composite fibres.

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