Microwave-assisted intercalation of 1-alkanols and 1,omega-alkanediols into alpha-zirconium phosphate. Evidence of conformational phase transitions in the bimolecular film of alkyl chains

摘要

A series of 1-alkanols and 1,omega-alkanediols with chain lengths ranging from 2 to 18 and 2 to 10 carbon atoms, respectively, was intercalated into alpha-Zr(HPO4)(2).H2O by exposing it, intimately dispersed with the guest species, to microwave radiation. The intercalation of 1-hexanol in the presence of different amounts of 1-propanol was also investigated. Thermogravimetric analysis showed that the intercalation compounds contained as a maximum 2 mol of alkanol or I mol of alkanediol per I mol of zirconium phosphate. The correlation between the interlayer distance of the samples, determined at room temperature, and the number of carbon atoms in the alkyl chain indicates that the alkanol molecules are arranged as an ordered bimolecular film in the interlayer region of the host. Differential scanning calorimetry analysis and X-ray powder diffraction patterns of representative samples taken at different temperatures showed a phase transition in which the bimolecular film undergoes a change from an all-trans conformation to a conformation in which the O-C-1-C-2-C-3 torsion angle changes from 180 to 136degrees. The temperature at which this phase transition occurs was found to increase with the increasing number of carbon atoms in the alkyl chain. Similar effects were observed with the 1,omega-alkanediol intercalates. [References: 19]