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Title: Novel polymer stabilised emulsions as reaction vessels and for particle synthesis
Author: Ur Rehman, Saif
ISNI:       0000 0004 7228 3273
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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This project is divided into three parts. In the first part control and selectivity over inter-droplet interactions was demonstrated. This was achieved by two type of pH responsive polymeric surfactants: cationic PDMAEMA based and anionic PSHEMA based branched copolymers. These surfactants were synthesised by thiol-regulated free-radical branching polymerisation. They showed excellent capability in inducing selective electrostatic assembly to the emulsion system triggered by change in pH. This controlled aggregation was easily reversed with the change in solution pH back to basic. Stability and aggregation of the emulsion system was characterised using laser diffraction and zeta potential. The results show that both cationic and anionic emulsions are stable, remain non-responsive and demonstrate no significant change in droplet size diameter at different pH if present in separate systems. Selective aggregation and increase in droplet size diameter was observed when both emulsions were mixed at pH2. Images obtained from confocal microscopy were in good agreement with laser diffraction and zeta potential data about the size of droplets. In the second and third part, the effects of polymeric surfactants in the fabrication of poly(3-hexylthiophene) (P3HT) nanoparticles and their optical properties were studied. Herein the solvent emulsion evaporation technique was exploited to fabricate P3HT nanoparticles of different sizes and tailor their optical properties. Linear triblock and star-block copolymers of different molecular weights and architectures were used to facilitate the fabrication of P3HT nanoparticles. Experiments confirmed that the molecular weight does affect the stability of the emulsion and ultimately the size and properties of nanoparticles. The P3HT particle size ranged from 170nm to 900 nm depending upon the molecular weight of the polymeric surfactant used during fabrication. The dispersion colour ranged from deep purple to violet red, which was also confirmed by UV-Vis characterisation. Characteristic peaks of P3HT were observed in all particles. The intensities of these peaks were different to each other, largely due to the size and morphology of the particles in solution. It was also noted that these particles showed strong fluorescence around 670 nm wavelengths. We have shown that it is possible to fabricate nanoparticles with pre-defined size and characteristics.
Supervisor: Georgiou, Theoni ; Stingelin, Natalie ; Weaver, Jon Sponsor: Islamic Development Bank
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral