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- Adsorption (1)
- Lignin modification (1)
- Metal-organic frameworks (1)
- Microporous materials (1)
- Mussel-inspired adhesive systems (1)
- N,O ligands (1)
- Zinc (1)
Organisationseinheit der BAM
- 6 Materialchemie (1)
- 6.3 Strukturanalytik (1)
Five distinct analytical techniques were compared for the quantification of the H2O (0·1-7·4 wt%) and D2O (up to 5·5 wt% D2O) contents in rhyolitic glasses. The hydrogen concentration in obsidians was measured using nuclear reaction analysis (NRA) and converted into H2O concentration. The bulk water content (H2O+D2O) of synthesised glasses was determined using thermal extraction in conjunction with KarlFischer titration (KFT). Unextracted H2O was measured by infrared (IR) spectroscopy after remelting the KFT products at high pressure. These well characterised glasses were subsequently used to calibrate secondary ion mass spectrometry (SIMS), infrared and evolved gas analysis (EGA). The calibrations of SIMS for H2O and D2O show a significant matrix effect at H2O and D2O concentrations larger than ~3 mol/l with the relative sensitivity factor (RSF) decreasing with bulk water content. Molar absorption coefficients for the OH stretching vibration band at 3570 cm-1 and the OD stretching vibration band at 2650 cm-1 in the infrared absorption spectra were reinvestigated. In the range 0·1-6 wt% the H2O content of glasses could be reproduced within analytical error using a constant linear molar absorption coefficient. However, it appears that the absorption coefficients for the 3570 cm-1 band as well as for the 2650 cm-1 band both decrease systematically with concentration of dissolved H2O and D2O (epsi3570=80 (±1) - 1·36(±0·23)CH2Ot and epsi2650=61·2(±1) - 2·52(± 0·30)CD2Ot). EGA allows quantification of the H2O content as well as the study of dehydration kinetics. It is shown that H2O is released under vacuum already at room temperature from glasses containing >7 wt% H2O.
We report on a new series of isoreticular frameworks based on zinc and 2-substituted imidazolate-4-amide-5-imidate (IFP-1–4, IFP=imidazolate framework Potsdam) that form one-dimensional, microporous hexagonal channels. Varying R in the 2-substitued linker (R=Me (IFP-1), Cl (IFP-2), Br (IFP-3), Et (IFP-4)) allowed the channel diameter (4.0–1.7 Å), the polarisability and functionality of the channel walls to be tuned. Frameworks IFP-2, IFP-3 and IFP-4 are isostructural to previously reported IFP-1. The structures of IFP-2 and IFP-3 were solved by X-ray crystallographic analyses. The structure of IFP-4 was determined by a combination of PXRD and structure modelling and was confirmed by IR spectroscopy and 1H MAS and 13C CP-MAS NMR spectroscopy. All IFPs showed high thermal stability (345–400°C); IFP-1 and IFP-4 were stable in boiling water for 7 d. A detailed porosity analysis was performed on the basis of adsorption measurements by using various gases. The potential of the materials to undergo specific interactions with CO2 was investigated by measuring the isosteric heats of adsorption. The capacity to adsorb CH4 (at 298 K), CO2 (at 298 K) and H2 (at 77 K) at high pressure were also investigated. In situ IR spectroscopy showed that CO2 is physisorbed on IFP-1–4 under dry conditions and that both CO2 and H2O are physisorbed on IFP-1 under moist conditions.
The 2-methoxyphenol units (G-units) in lignin are modified by demethylation and oxidation to provide the activated lignin as one part of an advanced biobased two-component (2K) adhesive system, which exhibits promising shear strengths in dry and underwater applications. The activation of lignin is straightforward and generates quinones via demethylation and periodate oxidation. These act as Michael acceptors and react smoothly with multi-thiol-star polymers to yield thiol-catechol connectivities (TCCs). The mussel-inspired material platform acts as a very robust and versatile adhesive, combining low-cost and readily available lignin with multi-thiols to achieve outstanding adhesion strengths of up to 15 MPa in dry application. In particular, the 2K system is compatible with the marine biological environment and shows no acute toxicity to sensitive organisms such as fish eggs. Thus, one possible application of this material could be an adhesive for setting temperature-resistant corals in damaged reefs.