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In this project we aim to produce a thermally triggered PLGA particulate gel, which is injectable and biocompatible. This will act as a scaffold for soft tissue repair. Three coating polymers were tested: Pluronics (PEG-PPG-PEG), poly(PPGMA-co-PEGMA) and poly(PNIPAm-DMA+). These were first tested as a dilute solution for clouding behaviour and then added to PLGA nanoparticles dispersions and tested rheologically for gel behaviour. These three polymers were chosen for their amphiphilic nature which may allow for surface attachment and decreasing miscibility with temperature. The PLGA copolymer in this work contained 75% lactic acid and 25% glycolic acid, and was made into a nanoparticle dispersion by interfacial deposition. The Pluronic L62 showed a promising cloud point temperature (Tclpt) of 37 °C, but did not show gel behaviour with the PLGA dispersions. It conferred thermally triggered aggregation, which may be useful as a drug delivery system. The poly(PPGMA-PEGMA) was synthesised using a free radical polymerisation feed method. These copolymers showed promising Tclpt values (20-37 °C) but only showed increased viscosity when heated at high concentration and when mixed with a PLGA dispersion. The structure-property relationships for these copolymers were analysed. Poly(NIPAM-DMA+) showed gelation at low concentrations without the particles, when the particle dispersion was added the gel maintained its strength up to 300% strain. This is unlike most particulate gels which tend to be brittle. Using cell culture the biocompatibility of these gels was tested. After 72 hours the cells appeared healthy and to be proliferating.

La pénurie d'eau est devenue un des problèmes clés à résoudre, et pour y faire face, il est nécessaire de disposer d'unités de traitement de l'eau efficaces. Au cours des dernières décennies la technologie des membranes est devenue l'une des techniques les plus prometteuses pour le traitement de l'eau. Néanmoins, les membranes ont une durée de vie limitée et sont, par ailleurs, sujettes à des phénomènes de colmatage - le dépôt, l'adsorption et l'absorption de particules dans la structure de la membrane -, ce qui réduit leur productivité, et augmente les coûts opérationnels. Une approche pour minimiser ce problème consiste à modifier des membranes hydrophobes, mécaniquement et chimiquement stables, en y greffant des matériaux amphiphiles afin de réduire le colmatage. L'objectif principal de ce travail est de caractériser les propriétés anti-colmatage des membranes de PVDF (Polyvinylidene fluoride) modifiées avec différents types de copolymères PS-PEGMA (Polystyrene - Poly(ethylene glycol) methacrylate), tout d'abord par l'utilisation de techniques classiques, puis, par le développement et / ou l'adaptation de techniques microfluidiques couplés à la microscopie à fluorescence et l'utilisation de la cartographie par microspectroscopie infrarouge à transformée de Fourier (IRTF). La cartographie IRTF a permis de quantifier localement le greffage et de mettre en évidence l'hétérogénéité du greffage sur la membrane. Ces cartes, représentant l'importance du greffage sur la membrane, ont par ailleurs été corrélées au dépôt de protéines sur la surface. Des systèmes microfluidiques ont également été développés pour caractériser sous microscope à fluorescence l'adsorption de protéines fluorescentes sur une membrane en présence d'un débit. Cette étude permet de suivre in situ et en dynamique l'adsorption (lors de cycles de filtration) et la désorption (lors de cycles de rinçage) de protéines sur la membrane. Ces mesures locales ont été mises en regard avec des mesures de permeabilité lors de cycles filtrations/rinçage mettant en évidence un rôle anti-fouling en particulier pour les copolymères tri-blocs ou pour les copolymères à enchaînement aléatoire. / Water scarcity has become one of the key issues to solve, and efficient water treatment is paramount to treat water sources. In recent decades membrane technology has become one of the promising solutions for water treatment. Nevertheless, membranes are prone to fouling phenomena - the deposition, adsorption, and absorption of particles in the membrane structure -, which hinders their life-span and productivity, and raise operative costs. One approach to minimize this issue is to modify the already mechanically and chemically stable hydrophobic membranes with amphiphilic materials. The main aim of this work is to characterise the anti-fouling properties of PVDF (Polyvinylidene fluoride) membranes modified with different types of PS-PEGMA (Polystyrene - Poly(ethylene glycol) methacrylate) copolymers, firstly by using classical techniques, and then, by developing and/or adapting new ones: microfluidic devices coupled with fluorescence microscopy, and the use of Fourier Transform Infrared microspectroscopy (FTIR mapping). FTIR mapping allowed the local detection of the coating layer and showed its heterogeneous distribution on the surface of the membrane. These maps, that represent the importance of the coating on the membrane, were correlated with the deposit of proteins on the surface. Microfluidic systems were also developed to characterise the adsorption of fluorescent proteins on the membrane under a fluorescent microscope in the presence of a flow. This study allowed the in-situ and dynamic follow-up of the adsorption - during filtration cycles - and of the desorption - during rinsing cycles - of the proteins on the membrane. These local measurements were compared against permeability measurements during the filtration/rinsing cycles evidencing the anti-fouling role of the copolymers used for the modification of the membranes, particularly for the triblock and random copolymers.

Cellulose is one of the most abundant biopolymers found in nature. Cellulose based derivatives have a number of advantages including recyclability, reproducibility, biocompatibility, biodegradability, cost effectiveness and availability in a wide variety of forms. Due to the benefits of cellulose based systems, this research study was aimed at developing novel cellulosic nanoparticles with potential pharmaceutical and personal care applications. Two different cellulosic systems were evaluated, each with its own benefits and proposed applications. The first project involves the synthesis and characterization of polyampholyte nanoparticles composed of chitosan and carboxymethyl cellulose (CMC), a cellulosic ether. EDC carbodiimide chemistry and inverse microemulsion technique was used to produce crosslinked nanoparticles. Chitosan and carboxymethyl cellulose provide amine and carboxylic acid functionality to the nanoparticles thereby making them pH responsive. Chitosan and carboxymethyl cellulose also make the nanoparticles biodegradable and biocompatible, making them suitable candidates for pharmaceutical applications. The synthesis was then extended to chitosan and modified methyl cellulose microgel system. The prime reason for using methyl cellulose was to introduce thermo-responsive characteristics to the microgel system. Methyl cellulose was modified by carboxymethylation to introduce carboxylic acid functionality, and the chitosan-modified methyl cellulose microgel system was found to be pH as well as temperature responsive. Several techniques were used to characterize the two microgel systems, for e.g. potentiometric and conductometric titrations, dynamic light scattering and zeta potential measurements. FTIR along with potentiometric and conductometric titration was used to confirm the carboxymethylation of methyl cellulose. For both systems, polyampholytic behaviour was observed in a pH range of 4-9. The microgels showed swelling at low and high pH values and deswelling at isoelectric point (IEP). Zeta potential values confirmed the presence of positive charges on the microgel at low pH, negative charges at high pH and neutral charge at the IEP. For chitosan-modified methyl cellulose microgel system, temperature dependent behaviour was observed with dynamic light scattering. The second research project involved the study of binding interaction between nanocrystalline cellulose (NCC) and an oppositely charged surfactant tetradecyl trimethyl ammonium bromide (TTAB). NCC is a crystalline form of cellulose obtained from natural sources like wood, cotton or animal sources. These rodlike nanocrystals prepared by acid hydrolysis of native cellulose possess negatively charged surface. The interaction between negatively charged NCC and cationic TTAB surfactant was examined and it was observed that in the presence of TTAB, aqueous suspensions of NCC became unstable and phase separated. A study of this kind is imperative since NCC suspensions are proposed to be used in personal care applications (such as shampoos and conditioners) which also consist of surfactant formulations. Therefore, NCC suspensions would not be useful for applications that employ an oppositely charged surfactant. In order to prevent destabilization, poly (ethylene glycol) methacrylate (PEGMA) chains were grafted on the NCC surface to prevent the phase separation in presence of a cationic surfactant. Grafting was carried out using the free radical approach. The NCC-TTAB polymer surfactant interactions were studied via isothermal titration calorimetry (ITC), surface tensiometry, conductivity measurements, phase separation and zeta potential measurements. The major forces involve in these systems are electrostatic and hydrophobic interactions. ITC and surface tension results confirmed two kinds of interactions: (i) electrostatically driven NCC-TTAB complexes formed in the bulk and at the interface and (ii) hydrophobically driven TTAB micellization on the NCC rods. Conductivity and surface tension results confirmed that the critical micelle concentration of TTAB (CMCTTAB) shifted to higher values in the presence of NCC. Phase separation measurements allowed us to identify the formation of large aggregates or hydrophobic flocs depending on the TTAB concentration. Formation of NCC-TTAB complexes in aqueous solutions was confirmed by a charge reversal from negative to positive charge on the NCC rods. The effect of electrolyte in shielding the negative charges on the NCC was observed from ITC, surface tensiometry and phase separation experiments. Several mechanisms have been proposed to explain the above results. Grafting of PEGMA on the NCC surface was confirmed using FTIR and ITC experiments. In phase separation experiments NCC-g-PEGMA samples showed greater stability in the presence of TTAB compared to unmodified NCC. By comparing ITC and phase separation results, an optimum grafting ratio (PEGMA : NCC) for steric stabilization was also proposed.

Cellulose is one of the most abundant biopolymers found in nature. Cellulose based derivatives have a number of advantages including recyclability, reproducibility, biocompatibility, biodegradability, cost effectiveness and availability in a wide variety of forms. Due to the benefits of cellulose based systems, this research study was aimed at developing novel cellulosic nanoparticles with potential pharmaceutical and personal care applications. Two different cellulosic systems were evaluated, each with its own benefits and proposed applications. The first project involves the synthesis and characterization of polyampholyte nanoparticles composed of chitosan and carboxymethyl cellulose (CMC), a cellulosic ether. EDC carbodiimide chemistry and inverse microemulsion technique was used to produce crosslinked nanoparticles. Chitosan and carboxymethyl cellulose provide amine and carboxylic acid functionality to the nanoparticles thereby making them pH responsive. Chitosan and carboxymethyl cellulose also make the nanoparticles biodegradable and biocompatible, making them suitable candidates for pharmaceutical applications. The synthesis was then extended to chitosan and modified methyl cellulose microgel system. The prime reason for using methyl cellulose was to introduce thermo-responsive characteristics to the microgel system. Methyl cellulose was modified by carboxymethylation to introduce carboxylic acid functionality, and the chitosan-modified methyl cellulose microgel system was found to be pH as well as temperature responsive. Several techniques were used to characterize the two microgel systems, for e.g. potentiometric and conductometric titrations, dynamic light scattering and zeta potential measurements. FTIR along with potentiometric and conductometric titration was used to confirm the carboxymethylation of methyl cellulose. For both systems, polyampholytic behaviour was observed in a pH range of 4-9. The microgels showed swelling at low and high pH values and deswelling at isoelectric point (IEP). Zeta potential values confirmed the presence of positive charges on the microgel at low pH, negative charges at high pH and neutral charge at the IEP. For chitosan-modified methyl cellulose microgel system, temperature dependent behaviour was observed with dynamic light scattering. The second research project involved the study of binding interaction between nanocrystalline cellulose (NCC) and an oppositely charged surfactant tetradecyl trimethyl ammonium bromide (TTAB). NCC is a crystalline form of cellulose obtained from natural sources like wood, cotton or animal sources. These rodlike nanocrystals prepared by acid hydrolysis of native cellulose possess negatively charged surface. The interaction between negatively charged NCC and cationic TTAB surfactant was examined and it was observed that in the presence of TTAB, aqueous suspensions of NCC became unstable and phase separated. A study of this kind is imperative since NCC suspensions are proposed to be used in personal care applications (such as shampoos and conditioners) which also consist of surfactant formulations. Therefore, NCC suspensions would not be useful for applications that employ an oppositely charged surfactant. In order to prevent destabilization, poly (ethylene glycol) methacrylate (PEGMA) chains were grafted on the NCC surface to prevent the phase separation in presence of a cationic surfactant. Grafting was carried out using the free radical approach. The NCC-TTAB polymer surfactant interactions were studied via isothermal titration calorimetry (ITC), surface tensiometry, conductivity measurements, phase separation and zeta potential measurements. The major forces involve in these systems are electrostatic and hydrophobic interactions. ITC and surface tension results confirmed two kinds of interactions: (i) electrostatically driven NCC-TTAB complexes formed in the bulk and at the interface and (ii) hydrophobically driven TTAB micellization on the NCC rods. Conductivity and surface tension results confirmed that the critical micelle concentration of TTAB (CMCTTAB) shifted to higher values in the presence of NCC. Phase separation measurements allowed us to identify the formation of large aggregates or hydrophobic flocs depending on the TTAB concentration. Formation of NCC-TTAB complexes in aqueous solutions was confirmed by a charge reversal from negative to positive charge on the NCC rods. The effect of electrolyte in shielding the negative charges on the NCC was observed from ITC, surface tensiometry and phase separation experiments. Several mechanisms have been proposed to explain the above results. Grafting of PEGMA on the NCC surface was confirmed using FTIR and ITC experiments. In phase separation experiments NCC-g-PEGMA samples showed greater stability in the presence of TTAB compared to unmodified NCC. By comparing ITC and phase separation results, an optimum grafting ratio (PEGMA : NCC) for steric stabilization was also proposed.

Surface functionalised silica materials have been prepared, followed by the extensive testing of their ability to remove metal ions from aqueous solutions. Modifications include ligand attachment and polymer grafting from the silica surface whilst the metals tested range from first row transition metals right through to the lanthanides and actinides. Characterisation of the materials produced has been of paramount importance for the understanding of the modification process and this is also extensively discussed. Atom transfer radical polymerisation (ATRP) has been used as the primary polymerisation method. Following polymerisation of 2-hydroxyethyl methacrylate (HEMA), post functionalisation was attempted. However, this was found to cause severe cross-linking and all attempts to attach ligands to this failed. Nonetheless, this process was transferred to grafting from silica surfaces and a novel approach to the characterisation of this material was implemented. (3-aminopropyl) triethoxysilane (APTES) was reacted with multiple forms of silica, primarily ZEOprep silica (average particle size 71.48 πm) and fumed silica (0.007 μm). This produced an amine coated surface to which 2-bromoisobutyryl bromide (BIBB) was attached, providing the required surface for radical polymerisation to proceed with a selected monomer. Solid State Nuclear Magnetic Resonance (SSNMR) has been utilised as the major characterisation technique for each step, leading to significant understanding of how this occurs. Thermogravimetric Analysis (TGA) and elemental analysis has supported this method at each stage whilst also enabling one to calculate the moles of APTES present, per gram of APTES-functionalised silica. For the ZEOprep silica this was calculated to be at up to 1.51 x 10-3 mol g-1 and for the fumed silica 1.63 x 10-3 mol g-1. As well as testing the selective nature of these materials, solutions of individual ions and radionuclides were used to measure the effectiveness of the materials for a specific ion. Rd values for these metals ions including solutions of Co(II), Ni(II), Cu(II), Cd2+, Eu(III) and [UO2]2+ have reached values ranging from 7.49 x 104 mL g-1 to as high as 2.17 x 109 mL g-1. These values are regarded as outstanding by other groups that have reported similar results and these are discussed in the report. This range includes values that were observed when competing Na+ and Ca2+ ions were present at 0.5 % and 1 % (w/w). pH testing was also investigated with the materials using a solution of europium ions to determine the most effective range and this was found to fall between pH 4 and 5. X-ray Photoelectron Spectroscopy (XPS) has been utilised to help gain an understanding of the binding between Cu(II) ions and APTES, suggesting that copper ions bind with oxygen atoms closer to the silica surface as well as the nitrogen atoms at the end of the ligand. Meanwhile STEM (Scanning Transmission Electron Microscope) has been used to show how effectively the surface area of the material is used by imaging the europium ions over a sample of APTES-functionalised fumed silica. Ligands and polymers have been focussed on to build a catalogue of functional materials and this has been achieved in collaboration with PhosphonicS Ltd. The most significant finding from these selective investigations was that uranyl ions were found to be the most readily removed. Cu(II) and Eu(III) ions were also removed relatively effectively whilst Co(II), Ni(II), Zn2+ and Cd2+ proved the most challenging but certainly not impossible. [UO2]2+ concentrations were reduced from 17.1 ppm to 1.6 ppm after 4 weeks with use of the ligand SEA (2-aminoethyl sulfide ethyl silica), even with six other metal ions present at similar initial concentrations and a starting pH of 4.67 by adding just 50 mg of the material to a 45 mL solution.