Supramolecular organization of ±camphor-10-sulfonic acid and N,N-dimethyl formamide into giant spherulites

Abstract

Cast films of ±camphor-10-sulfonic acid (CSA) from N,N-dimethyl formamide (DMF) produced giant spherulites (diameter ≈ 1 cm) after isothermal crystallization at 50-62 °C. They did not exhibit any color under ordinary visible light, but when observed through a polarizing microscope, they showed different colors at different angles of the polarizer. The color also depends on thickness of the film from which giant spherulites are produced. IR study indicates supramolecular organization of CSA and DMF by H bonding, and elemental analysis suggests that the complex be produced in a 1:1 molar ratio of the components. The X-ray and differential scanning calorimetry study concludes that the supramolecular crystal is different from that of CSA. Similar results are obtained when cast films of CSA from N,N-dimethyl acetamide are crystallized but casting from methyl formamide/formamide produce only liquid crystalline texture.