Morphological control in the solution crystallisation of polymeric nanoparticles

Chapter One gives a broad introduction to the research described herein, initially discussing the reasons for morphology control, polymerisation techniques and self- assembly methods. A general introduction to solution crystallisation of polymers is given, with a focus on block copolymers with a crystalline core-forming block. Chapter Two discusses the use of various poly(L-lactide) based amphiphiles to propose a unimer solubility-based shape selectivity mechanism for the formation of 1D and 2D nanostructures, leading to a single component solution phase protocol for the preparation of uniform diamond-shaped platelets. Chapter Three considers the use of three different morphologies, namely spheres, cylinders and platelets, as nanocomposites in calcium alginate hydrogels, where a greater shear strength is measured for platelet-composite hydrogels. Chapter Four utilises the proposed unimer solubility approach to create 2D diamond-shaped platelets of controlled size and shape. The use of different size platelets as water-in-water Pickering emulsifiers is explored, where larger plates are shown to give more stable emulsions. Chapter Five employs the use of a poly(ɛ-caprolactone) crystallisable core-forming block for the preparation of 1D cylindrical structures of controlled length and dispersity. Direct epitaxial growth in water is shown, leading to the preparation of strong hydrogel materials. Chapter Six summarises the research presented, giving general conclusions as well as discussing the scope for future investigations in this area of research

Frequency reconfigurable patch antenna for 4G LTE applications

A compact printed multi-band frequency reconfigurable patch antenna for 4G LTE applications is presented in this paper (50 x 60 x 1.6 mm3). The antenna consists of W-shaped and Inverted-U shaped patch lines connected in a Tree-shape on the front side of the antenna. The back-side of the antenna contains a 90°-tilted T-shaped strip connected with an Inverted-L shaped strip which is shorted with a patch on the front side for increasing the electrical length to cover lower frequency bands. Frequency reconfigurability is achieved by inserting three switches i.e., PIN diodes. The most critical part of this work is the designing of RLC-based DC line circuits for providing the DC biasing to the PIN diodes used as switches and inserting them at optimum locations. This antenna is reconfigurable among eight different 4G LTE frequency bands including 0.9 GHz, 1.4 GHz, 1.5 GHz, 1.6 GHz, 1.7 GHz, 1.8 GHz, 2.6 GHz, 3.5 GHz and WLAN band 2.5 GHz. The antenna exhibits different radiation patterns having a different direction of peak gain at different frequencies and for different switching combinations. The antenna is simulated with CST, and a prototype is fabricated to compare the measured and simulated results with good accuracy

Hookworm infestation as a cause of melena and severe anaemia in farmer

Abstract Hookworm infections remain a major cause of morbidity in the developing world. Prevalence is highest in agricultural areas, where use of waste water for irrigation and poor hygiene increases infection rates among farmers. Infections present with gastrointestinal symptoms and chronic anaemia, and there are usually no signs of overt blood loss.The following report describes a case of melena in a middle-aged farmer, where the diagnosis of hookworm infestation was delayed due to the unusual presentation. The patient underwent multiple blood transfusions before referral to the Aga Khan University Hospital (AKUH), Karachi and was managed conservatively with mebendazole at our hospital after exclusion of other possible causes of gastrointestinal bleeding. This case highlights the importance of considering hookworm infestations as a cause of melena in the older age group, where other critical differentials such as peptic ulcer disease and occult malignancy may result in delay in initiation of treatment and a significant financial burden on the patient

Controlling the size of two-dimensional polymer platelets for water-in-water emulsifiers

A wide range of biorelevant applications, partic- ularly in pharmaceutical formulations and the food and cosmetic industries, require the stabilization of two water-soluble blended components which would otherwise form incompatible biphasic mixtures. Such water-in-water emulsions can be achieved using Pickering stabilization, where two-dimensional (2D) nanomateri- als are particularly effective due to their high surface area. However, control over the shape and size of the 2D nanomaterials is challenging, where it has not yet been possible to examine chemically identical nanostructures with the same thickness but different surface areas to probe the size-effect on emulsion stabilization ability. Hence, the rationale design and realization of the full potential of Pickering water-in-water emulsion stabilization have not yet been achieved. Herein, we report for the first time 2D poly(lactide) platelets with tunable sizes (with varying coronal chemistry) and of uniform shape using a crystallization-driven self-assembly methodology. We have used this series of nanostructures to explore the effect of 2D platelet size and chemistry on the stabilization of a water-in-water emulsion of a poly(ethylene glycol) (PEG)/dextran mixture. We have demonstrated that cationic, zwitterionic, and neutral large platelets (ca. 3.7 × 10 6 nm 2 ) all attain smaller droplet sizes and more stable emulsions than their respective smaller platelets (ca. 1.2 × 105 nm 2 ). This series of 2D platelets of controlled dimensions provides an excellent exemplar system for the investigation of the effect of just the surface area on the potential effectiveness in a particular applicationPostprint (published version

Core functionalization of semi-crystalline polymeric cylindrical nanoparticles using photo-initiated thiol–ene radical reactions

Sequential ring-opening and reversible addition–fragmentation chain transfer (RAFT) polymerization was used to form a triblock copolymer of tetrahydropyran acrylate (THPA), 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) and L-lactide. Concurrent deprotection of the THPA block and crystallization-driven self-assembly (CDSA) was undertaken and allowed for the formation of cylindrical micelles bearing allyl handles in a short outer core segment. These handles were further functionalized by different thiols using photo-initiated thiol–ene radical reactions to demonstrate that the incorporation of an amorphous PMAC block within the core does not disrupt CDSA and can be used to load the cylindrical nanoparticles with cargo

Understanding the CDSA of poly(lactide) containing triblock copolymers

Using crystallization driven assembly (CDSA) the simple preparation of well-defined tuneable 1D and 2D structures based on poly(lactide) triblock copolymers is demonstrated.</p