Pure and Applied Chemistry

Abstract: The morphology of blends of two types of hydrogen-bonding systems was studied with a view to understanding the effect of blending on the extent of hydrogen bonding and changes in the morphology.One of them is the long-chain carbamate with a C₁₈ alkyl side chain, and the other is stearic acid, which also has a C₁₇ alkyl chain. At low concentrations, the C₁₈ carbamate reduces the size of the crystals of stearic acid. However, the stearic acid has no effect on the morphology of the carbamate. The morphological changes are due to the disruptive packing of the alkyl chains, rather than a change in the extent of hydrogen bonding. The blends of homologous carbamates studied before [Moniruzzaman, Goodbrand, Sundararajan, J. Phys. Chem. Part B 107, 8416 (2003)] are more effective in mutually controlling the spherulite size and imparting transparency than the carbamate/stearic acid blend. The presence of the carbamate as the minor component changes the ratio of the intensities of the X-ray reflections at 2 (theta)=21.6 and 2.21°. It is found that in the blends with the carbamates quenched from the melt, the stearic acid exhibits a polymorphic transition from the E to the C form in the differential scanning calorimetry (DSC) analysis.