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Different experimental techniques were applied to study thermal and structural properties, strength of H-bonds, possible keto - enol tautomerism and molecular dynamics at various thermodynamic conditions in the H-bonded active substance, curcumin (CRM). Dielectric measurements revealed dynamical features of examined compound that are uncharacteristic for the associated systems. This includes enormously large pressure coefficient of the glass transition temperature and prominent drop of the fragility with compression. Simultaneously, the shape of α -process slightly broadened at elevated pressures. Infrared investigations demonstrated that this effect is related to the variation in the population of H-bonds. Moreover, we studied the changes in the structural and dynamical properties of the glasses prepared upon cooling of the melt (ordinary glass, OG) and the one obtained after compression of CRM in the liquid phase and decompression at T = 293 K (dense glass, DG). Interestingly, during the aging of the latter sample, a clear shift of the β -relaxation towards higher frequencies was noted. This unexpected result indicated that the density of DG is probably getting smaller with time. Complementary X-ray diffraction experiments confirmed this supposition. Additionally, they showed that in DG there are traces of polymorph II of CRM that has a higher density than initial crystals (polymorph I). Finally, infrared studies demonstrated that H-bond pattern in DG is slightly different with respect to OG. Furthermore, Raman investigations suggested that probably keto - enol tautomerism might be shifted towards diketo form in the glass obtained at high compression. Our investigations are very interesting in the context of better understanding of the behavior of associated systems at high compression as well as provide a better insight into dynamics of higher density glasses produced at elevated pressures. Unlabelled Image [ABSTRACT FROM AUTHOR]

This work demonstrates the effect of a high dc bias field (up to 160 kV/cm) on the polyaddition reaction of the modeled epoxy resin system. Polymerization of bisphenol A diglycidyl ether (DGEBA) supported by high electric field results in obtaining epoxides with significantly increased molecular weight, which is seven-fold higher than the zero-field reference (M n = 4.7 kg/mol). We also found a markedly reduced dispersity (Ð = 1.52 at 0 kV/cm, Đ = 1.21 at 160 kV/cm). The molecular weight and dispersity of obtained polymers change almost linearly with the reaction time. By following polymerization kinetics in the real-time of the experiment, via dielectric spectroscopy, we observe slowing down the reaction progress at dc fields of E = 160 kV/cm, compared to the zero-field case, E = 0 kV/cm. The polymer materials obtained in the presence/absence of static electric fields exhibit distinctly different glass transition temperatures. Our study highlights a better control over the reaction and product properties attained by using only the magnitude of the applied field as the control variable. Thus, a high electric field could provide an alternative pathway in synthesizing and developing advanced polymer materials using simpler, "green", less-expensive, and technologically demanding approaches. [Display omitted] [ABSTRACT FROM AUTHOR]