Cs2Zn(CN)4: a first example of a non-cyano spinel of composition A2M(CN)4 with A=alkali metal and M=group 12 metal

The crystal structure of monoclinic Cs2Zn(CN)4 (C2/c, Z = 4) was solved and refined from high-resolution synchrotron powder diffraction data (ESRF: Swiss-Norwegian beamline). In contrast to all other known cyanides of composition A2M(CN)4 with A = alkali metal and M = group 12 metal, which crystallize in cubic or rhombohedrally distorted spinel variants and thus with A+ in an octahedral coordination, the Cs+ cation in Cs2Zn(CN)4 shows an eight-fold coordination by CN− anions of the [Zn(CN)4]2− tetrahedra. Upon heating, no phase transition is observed. Instead, a reversible melting at approx. T = 380°C occurs.

Reversible Colloidal Crystallization

We report 3D colloidal self-assembly (crystallization) of poly(ionic liquid) latexes to produce crystals that exhibit reversible melting and recrystallization in water, due to “classical” interparticle interactions, typical of multifunctional polymers. These new materials are derived from an ionic liquid monomer that is polymerized at room temperature by redox-initiated polymerization. Particle synthesis, self-assembly, thermal properties, and introductory light diffraction effects are reported with a focus on melting. These crystals are distinguishable from classical colloidal crystalline arrays, and are the first such crystals to exhibit thermal melting. This new hydrogel offers promise for engineering large volume production of photonic crystals active in the visible and proximal spectral regions, by crystallization from suspension (solution), characteristic of most useful chemical compounds.

Structural changes of layered alkylsiloxanes during the reversible melting–solidification process

Structural changes of layered alkylsiloxanes occurring during the reversible melting–solidification process were investigated by in situ XRD and NMR.

Mechanical Relaxations and Transitions in Poly(Vinylidene Fluoride) PVDF

Dynamic mechanical spectroscopy and differential scanning calorimetry measurements carried out on PVDF films are reported. Several mechanical relaxations are observed around - 100° C, -40° C, and 17° C at 1 Hz, respectively. It is shown that thermomechanical treatments induce variation of material morphology as revealed by calorimetry and low-frequency mechanical spectroscopy. The effect of long-term ageing at room temperature is attributed to reversible melting and formation of small crystallites. The molecular rearrangements involved in ageing at room temperature are characterized by a slow dynamics.