Eugene G. Joseph

Effect of thermal history on the morphology of thermotropic liquid crystalline copolyesters based on PET and PHB

Abstract Morphological studies were carried out on thermotropic liquid crystalline copolyesters based on poly(ethylene terephthalate) (PET) and para-hydroxybenzoic acid (PHB), where PHB content varied from 30 mole percent up to 80 mole percent. The technique of chemical etching, using n-propylamine as the etchant, coupled with scanning electron microscopy was utilized to obtain structural information. Scanning electron microscopy results on chemically etched, compression moulded films show that selective chemical etching of the PET rich regions occur. This indicates that the morphology of the copolymers is hetergeneous in nature. Further support regarding a hetergeneous morphology was obtained by transmission electron microscopy. A morphological model has been proposed based on these results. The observance of non-equilibrium behaviour associated with amorphous PET regions (as seen from d.s.c. measurements) also strongly indicates the presence of a phase rich in PET and thus supports the non-homogeneous morphological model. Thermal analysis of these copolyesters suggests that the chain structure is non-random and this is an agreement with results published by Wunderlich et al. The glass transition temperature typically associated with PET is present and remains constant in all copolymers compositions where PET is the continuous phase. Further, the melting temperatures obtained experimentally are higher than the values predicted by theory for random copolymers and the melting endotherms are relatively narrow. These observations also indicate a non-random chain structure. Structural studies conducted on films compression molded at different temperatures show that morphological rearrangement occurs at higher temperatures with the formation of domains of the order of 10 microns.

Preliminary Thermal and Structural Studies of Blends Based on a Thermotropic Liquid Crystalline Copolyester and Poly(Ethylene) Terephthalate

Due to economic, technological, and regulatory pressures, there has been a gralual narrowing of the chemical variety of polymers being produced1. In order to obtain new materials with unique properties, one of the approaches taken by polymer scientists is to use polymer blends. Some of the reasons as to why these materials are attractive are (i) the ability to obtain higher performance materials economically, (ii) modification of performance as a market develops, (iii) extend the performance of an expensive resin and (iv) re-use of plastics scrap through blending and (v) genetation of a unique material in terms of processability or performance1. The two principal means by which polymer blends can be prepared are mechanical mixing or casting from solution.

Studying the activity of antitubercluosis drugs inside electrospun polyvinyl alcohol, polyethylene oxide, and polycaprolacton nanofibers.

The activity of antituberculosis drugs (streptomycin sulfate, isoniazid, pyrazinamid, and clarithromycin) embedded in biodegradable nanofibers against Mycobacterium avium has been studied by broth dilution assay and by agar plate assay. These drugs have also been embedded in electrospun polyvinyl alcohol (PVA), polyethylene oxide (PEO), and polycaprolacton (PCL) nanofibers to design a new single tablet containing first-line antituberculosis drugs. Our results show that antituberculosis drugs are active at tiny amounts (up to 300 µg mL(-1) of solvent). However, within polymer matrices, high amounts of drugs are required to avoid unwanted weak interactions within PEO and PCL matrices. The successful design of a single tablet containing required amounts of antituberculosis drugs is essential for the full treatment of tuberculosis in patients with HIV.

Designing and testing single tablet for tuberculosis treatment through electrospinning

Abstract Drug delivery systems refers to systems designed to transport or deliver drugs to treat a certain infected organ. Generally, these systems include loading of the drug and effective substances on a carrier (nanofibers, nanoparticles, nanorods, capsule, or matrix) and delivering these substances to the infected organs. The drugs can be used in the form of dispersion, emulsion, bandages, gels, creams, or as tablets. Developing controllable drug delivery systems allow them to be utilized in wide medical applications as wound dressings, skin treatments, or to treat internal infected organs. In this work, tuberculosis drugs (pyrazinamide, isoniazid, clarithromycin, and streptomycin) are loaded on poly(e-caprolactone), poly(ethylene oxide), and poly(vinyl alcohol) nanofibers to design single tablets suitable for HIV patients. The activity of these drugs loaded on the nanofiber is tested against Mycobacterium avium through broth dilution assay and by agar plate assay. The minimal inhibitory concentration and the minimal bactericidal concentration are also studied.