Diversity and Structure-Property Correlation in Disordered Multicomponent Organic Crystal Forms

Abstract

The search for new multifunctional materials continues unabated, and with the realization that in solids, the material property can be tailored using the variability provided by molecular and submolecular forces. Harnessing intermolecular interactions in organic multicomponent systems forms the basis of the work described in this thesis. Model studies to unravel the variety of energetically favourable arrangements to either augment or generate anticipated physico-chemical properties are presented in three chapters. The relationship between subtle variations in intermolecular interactions involving halogens in solid solutions of different stoichiometries and the ensuing tuning ability of mechanical properties are described in Chapter 2. The property of mechanical bending, plastic as well as elastic, in methodically designed “solid solution of cocrystals” and its correlation with halogen bonded networks forms the basic theme of this work. The hitherto unexplored microstructural organization in organic eutectics is outlined using a series of cognate experiments involving variable temperature synchrotron X-ray powder diffraction, variable temperature high-resolution Raman spectroscopy, and electron microscopy form the content of Chapter 3 & 4. The enigma of the powder diffraction data depicting the components as a mixture while the bulk melting point is unique and is lower than the melting points of the individual components is sorted out. The final chapter describes the construction of a cheap, environmental friendly, and easy to synthesize ultrahigh proton conducting material based on salt cocrystals of amino acids and oxalic acid. It is observed that these materials possess the highest proton conductivity value (3.03 * 10-2 S cm-1 at 60 °C and 95% RH) among all pure organic-based materials designed and reported so far in the literature.