Grinding-induced equimolar complex formation between thiourea and ethenzamide.
We prepared and characterized a grinding-induced equimolar complex of thiourea with ethenzamide. When thiourea and ethenzamide were co-ground at a molar ratio of 3 : 1, new powder X-ray diffraction (PXRD) peaks were observed in addition to PXRD peaks of thiourea crystals. The optimum stoichiometry of the new structure was confirmed as 1 : 1 mol/mol. Effect of grinding time on the thiourea-ethenzamide equimolar complex formation was investigated by using PXRD, differential scanning calorimetry and Fourier transform infrared spectroscopy. The equimolar crystal structure was confirmed by X-ray diffraction measurements of the single crystal which was recrystallized from ethanol. It was found that the intermolecular hydrogen bond formations between thiourea and ethenzamide molecules contributed to the equimolar complex formation. The complex formation was not observed in the cases where benzamide, salicylamide or 3-ethoxybenzamide was co-ground with thiourea. 2-Alcoxyl benzamide structures should be required for the grinding-induced equimolar complex formation with thiourea.
Salicylic acid/gamma-cyclodextrin 2:1 and 4:1 complex formation by sealed-heating method.
A novel complex of salicylic acid (SA) and gamma-cyclodextrin (gamma-CD) was obtained via the sealed-heating method. The influence of the water content of gamma-CD on the complex formation with SA by sealed-heating process was investigated. Quantitative determination of SA revealed that sealed-heated samples of SA and gamma-CD with low water content (0.8-5.4%) formed the SA/gamma-CD = 2:1 complex, while the samples with high water content (8.5-11.5%) formed the SA/gamma-CD = 4:1 complex. The molecular arrangements of gamma-CD in 2:1 and 4:1 complexes were determined by powder X-ray diffraction measurements to be in monoclinic-columnar and tetragonal-columnar forms, respectively. The results of infrared spectroscopy and (13)C solid-state NMR measurements showed that two types of SA molecules resided in the 4:1 complex, whereas only one type of SA molecules existed in the 2:1 complex. The obtained 2:1 complex was assumed to contain two SA molecules per one gamma-CD, with the SA molecules existing in the intermolecular spaces formed by the gamma-CD columns. In the case of the 4:1 complex, two SA molecules were incorporated into the intermolecular spaces while the other two SA molecules were included within the gamma-CD cavity.
Degradable polymers : principles and applications
1. Why Biodegradable Polymers? G. Scott. 2. An Overview of Biodegradable Polymers and Biodegradation of Polymers S.H. Huang. 3. Degradation and Stabilization of Carbon-Chain Polymers G. Scott. 4. Techniques and Methods of Polymer Degradation S. Karlsson, A.-C. Albertsson. 5. Biodegradation of Aliphatic Polyesters Suming Li, M. Vert. 6. Starch-Polymer Composites C. Bastioli. 7. Polymers from Renewable Sources E. Chiellini, et al. 8. Sustainable Poly(Hydroxyalkanoate) (PHA) Production G. Braunegg. 9. Polyhydroxyalkanoates: Properties and Modification for High Volume Application I. Chodak. 10. Biodegradable Polymers in Medicine E Piskin. 11. Environmentally Biodegradable Water-Soluble Polymers G. Swift. 12. Plastics and the Environment J. Guillet. 13. Degradable Hydrocarbon Polymers in Waste and Litter Control G. Scott, D.M. Wiles. Subject Index.