The α-relaxation process in polymethylphenylsiloxane was studied over a broad temperature and pressure range by dielectric spectroscopy. In the vicinity of the glass temperature, the shape of the dielectric loss peak is independent of both temperature and pressure. The steepness index (fragility), describing the temperature dependence of the relaxation times, is also independent of pressure (and of molecular weight as well). Thus, the correlation between fragility and nonexponentiality of the relaxation function is maintained under conditions of high compression. The combined temperature and pressure dependences of the relaxation time conformed to the Avramov equation. This model offers a means to relate the relaxation behavior to thermodynamic properties of the material.

A series of five alcohols (3-methyl-2-butanol, 1-cyclopropylethanol, 1-cyclopentylethanol, 1-cyclohexylethanol, and 1-phenylethanol) was used to study the impact of the size of steric hindrance and its aromaticity on self-assembling phenomena in the liquid phase. In this Letter, we have explicitly shown that the phenyl ring exerts a much stronger effect on the self-organization of molecules via the O–H···O scheme than any other type of steric hindrance, leading to a significant decline in the size and concentration of the H-bonded clusters. Given the combination of calorimetric, dielectric, infrared, and diffraction studies, this phenomenon was ascribed to its additional proton-acceptor function for the competitive intermolecular O–H···π interactions. The consequence of this is a different packing of molecules on the short- and medium-range scale.

Metal–organic frameworks (MOFs), formed of metal centers coupled by organic molecules, exhibit inherent porosity and crystallinity. Although these systems have been examined for many potential applications, their multiferroic properties remain poorly understood. One of the approaches to get an insight into the ferroic features of these materials is the study of frameworks templated by protonated organic molecules possessing rotational and conformational freedom. The embedded organic cation with an internal electric dipole moment may be ordered on cooling, leading to the appearance of ferroelectric-like properties. Herein, we report a study of two structural phase transitions in one such material, the methylhydrazinium zinc formate [CH₃NH₂NH₂][Zn(HCOO)₃] framework (MHyZn), using various experimental techniques. High-temperature (HT) improper ferroelectric phase transition and low-temperature (LT) biferroic phase transition in MHyZn single crystals have been investigated in a broad temperature range using X-ray diffraction, longitudinal ultrasonic velocity and attenuation measurements, pyrocurrent measurements, and broadband dielectric spectroscopy. In addition, noncentrosymmetric to centrosymmetric structural transformation was confirmed for the HT phase transition with the use of temperature-resolved second harmonic generation on powder samples, while polarizing microscopy observation of a large deformation of ferroelastic-like domains attested to the noncontinuous character of the crystallographic system transformation (trigonal to triclinic) in the LT biferroic phase transition. Finally, we proved that the spontaneous electric polarization occurs due to freezing of motion around the 2- and 3-axes of the methylhydrazinium cation.

Acetamidinium manganese formate undergoes a phase transition from the Imma to the P 2 ₁ / n structure at 304 K and magnetic order below 9 K.

Non-monotonic changes in the static and dynamic properties of a series of phenyl alcohols were assigned to the interplay between the dispersive forces and H-bonding interactions.