Reversible, nondegradative conversion of crystalline aromatic poly(ether ketone)s into organo-soluble poly(ether dithioketal)s

Crystalline aromatic poly(ether ketone)s Such as PEEK and PEK may be cleanly and reversibly derivatized by dithioketalization of the carbonyl groups With 1,2-ethanedithiol or 1,3-propanedithiol under strong acid conditions. The resulting 1,3-dithiolane and 1,3-dithiane polymers are hydrolytically stable, amorphous, and readily soluble in organic solvents such as chloroform and THF and are thus (unlike their parent polymers) easily characterized by gel permeation chromatography (GPC). GPC analysis of a range of derivatized PEEK samples using light-scattering detection revealed, in some instances, a bimodal molecular weight distribution with a small but potentially significant (and previously undetected) very high-molecular-weight fraction.

A synthetic tripeptide as a novel organo-gelator: a structural investigation

A self-associating synthetic tripeptide [Boc-Ala(1)-Aib(2)-beta-Ala(3)-OMe (Aib: alpha-amino-isobutyric acid, beta-Ala: beta-alanine)] forms thermoreversible transparent gels in various organic solvents and this offers the first example of a peptide gelator whose molecular self-assembly afforded for gelation has been characterised by single-crystal X-ray diffraction and FT-IR and NMR spectroscopic studies. The crystal structure of an analogous synthetic non-gelator tripeptide [Boc-Ala(1)-Gly(2)-beta-Ala(3)-OMe] is also discussed in light of the self-assembly of the gelator tripeptide. (C) 2003 Elsevier Science Ltd. All rights reserved.

Have increased dissolved organic carbon (DOC) losses from UK peat and organo-mineral soils been driven by the decline in acid rain?

Dissolved organic carbon (DOC) concentrations have been rising in streams and lakes draining catchments with organic soils across Northern Europe. These increases have shown a correlation with decreased sulphate and chloride concentrations. One hypothesis to explain this phenomenon is that these relationships are due an increased in DOC release from soils to freshwaters, caused by a decline in pollutant sulphur and sea-salt deposition. We carried out controlled deposition experiments in the laboratory on intact peat and organomineral O-horizon cores to test this hypothesis. Preliminary data showed a clear correlation between the change in soil water pH and change in DOC concentrations, however uncertainty still remains about whether this is due to changes in biological activity or chemical solubility.