Thermochromatism and structural evolution of metastable polydiacetylenic crystals.
Topochemically polymerized sodium 10,12-pentacosadiynoate (PCDA-Na) microcrystals show an irreversible red-to-blue chromatic transition accompanied by a distinct structural evolution upon initial thermal treatment, and show a subsequent completely reversible blue-to-red chromatic transition upon further thermal stimuli. Visible absorption spectroscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC) are used to investigate the thermochromatic transition behavior of the polydiacetylenic microcrystals. Brief quantum mechanical geometry optimization is employed to explain the lattice dimensional change during the irreversible red-to-blue chromatic transition of the metastable polydiacetylenic crystals.
Functionalisation of silica-carbonate biomorphs.
Biomorphs are a unique class of self-organised silica-carbonate mineral structures with elaborate shapes. Here we report first approaches to modify these complex inorganic architectures through silane chemistry, binding of nanoparticles, and organic polymerisation. This leads to functional nanostructures in which the complexity of the originally inorganic template is preserved, and offers new diagnostic tools to study the mechanisms underlying their formation.
Macroscopic single crystals of polymers by solid-state polymerization: a study of the monomer to polymer phase transformation of 1,6-dicarbazolyl hexadiyne
The solid-state polymerization of 1,6-di(N-carbazolyl-2,4-hexadiyne (DCH) giving rise to macroscopic single crystals of the corresponding polymer is described with regard to structural aspects. The crystal structures of the monomer and polymer are discussed with respect to the observed solid-state reactivity. An autocatalytic acceleration in the conversion-time characteristics of the radiation-induced polymerization is attributed to a non-destructive phase transition as indicated by a sudden change in the lattice parameters and the elastic constants of the polymerizing crystal. The same phase transition occurs with destruction of the parent lattice during thermal polymerization. The Young's modulus in the chain direction of radiation-polymerized crystals reaches the theoretical value expected for infinitely long polymer chains.