Novel solid state properties of drugs, polymers and various chemicals by thermal and analytical techniques.

摘要

I have observed unique variations in AC electrical conductivity of solids by dielectric analysis (DEA or DETA) when studied with respect to temperature and frequency. A wide range of solids were examined for this study e.g. organics, polymers, carbohydrates, API's (active pharmacy ingredients) and amino acids. Experimental results clearly show novel dielectric behavior of a linear increase in a log ionic conductivity vs. temperature in the pre-melt (20 to 30°C below the melt temperature) and melt transition regions. We have differentiated the solids which show the conductivity variations in pre-melt from those which do not e.g. pre-melt conductivity variations observed with polar polymers such as nylons and acetal vs. not observed in nonpolar polymers such as polyethylene, polypropylenes and long chain alkanes e.g. tetraconsane and pentacosane.;Isothermal dielectric analysis was used to study the cause of this variation in solids which yielded a polarization time property. The effect of various experimental factors on the results such as the effect of heating rate, varying the frequency, and sample size on the dielectric variations in the pre-melt temperature range have been studied. Correlating dielectric with calorimetric analyses gave us a better understanding of solid state properties. Calorimetric analysis was used to assure that the observed variations in the solid state properties are not due to moisture or impurities present in the sample. The ASTM E928-08 "Standard Test Method for Purity by Differential Scanning Calorimetry (DSC)" was employed to verify the purity of the experimental chemicals used in this study e.g. Acetanilide, Acetophenitidine and Vanillin.;Activation energies were calculated based on Arhennius behavior to better interpret the changes in the solid. As the different chemicals were heat cool cycled they were more amorphous, as evidenced by the decreasing activation energy for charge transfer with an increasing amorphous content. Morphological studies done by scanning electron microscopy (SEM) showed mechanical variations of the solid state in the pre-melt temperature range when treated with dielectric field. These mechanical variations can be related to the changes in the pre-melt temperature range for the solid state.;To explore the cause and effect relationship between structure and enhanced electrical conductivity, we have conducted a number of reactions with and without the AC dielectric field to ascertain if it is affecting the reaction rate or products. The most predominant reaction of all experiments to date was of a reducing amino acid and carbohydrate which showed enhanced reaction rate in the dielectric field. Dielectric analyses of the materials were further investigated by evaluating malaria driven proteins and poly peptides to develop a sensor for detecting malaria.