Hynek Beneš

Characterizing Crystal Disorder of Trospium Chloride: A Comprehensive,13C CP/MAS NMR, DSC, FTIR, and XRPD Study

Analysis of C cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and X-ray powder diffraction data of trospium chloride (TCl) products crystallized from different mixtures of water-ethanol [φ(EtOH) = 0.5-1.0] at various temperatures (0°C, 20°C) and initial concentrations (saturated solution, 30%-50% excess of solvent) revealed extensive structural variability of TCl. Although (13) C CP/MAS NMR spectra indicated broad variety of structural phases arising from molecular disorder, temperature-modulated DSC identified presence of two distinct components in the products. FTIR spectra revealed alterations in the hydrogen bonding network (ionic hydrogen bond formation), whereas the X-ray diffraction reflected unchanged unit cell parameters. These results were explained by a two-component character of TCl products in which a dominant polymorphic form is accompanied by partly separated nanocrystalline domains of a secondary phase that does not provide clear Bragg reflections. These phases slightly differ in the degree of molecular disorder, in the quality of crystal lattice and hydrogen bonding network. It is also demonstrated that, for the quality control of such complex products, (13) C CP/MAS NMR spectroscopy combined with factor analysis (FA) can satisfactorily be used for categorizing the individual samples: FA of (13) C CP/MAS NMR spectra found clear relationships between the extent of molecular disorder and crystallization conditions.

Influence of sol-gel conditions on the final structure of silica-based precursors

Abstract This work studied the solvent-free sol–gel process of (3-glycidyloxypropyl)trimethoxysilane using three different experimental setups and a ternary amine (DABCO) or a tin-based compound (DBTL) as the sol–gel catalysts, which allowed to prepare homogeneous liquid products and control their final microstructures. The aim was to synthesize epoxy-functionalized precursors for hybrid epoxy-based materials. The NMR spectroscopy, MALDI-TOF, DLS, FTIR and SEC were used to characterize the obtained sols and xerogels. The formed silica structures were primarily dependent on the type of catalyst used, but small cyclic structures were always present. Nevertheless, the DABCO-catalyzed system showed a higher tendency to create cage-like structures in contrast to the system that used DBTL catalyst in which larger ladder-like structures prevailed. The sols as well as the final xerogels with the higher condensation degree of alkoxysilane bonds were prepared under the basic (DABCO) conditions. All prepared liquid products (sols) were well miscible with epoxy pre-polymers and therefore can be considered as suitable epoxy-functionalized precursors for preparation of hybrid materials based on epoxy matrix.