Novel water-soluble polymers, N -(γ-propanoyl-valin)-chitosan and N -(γ-propanoyl-aspartic acid)-chitosan, were synthesized by reaction of low molecular weight chitosan with N α -(3-bromopropanoyl)-valine and N α -(3-bromopropanoyl)-aspartic acid, respectively, under mild conditions. Prior to reaction with chitosan, the peptide substituents have been prepared by standard peptide chemistry methods from 3-bromopropanoic acid and the relevant α-amino acid tert -butyl esters. The chemical structure and physical properties of the novel chitosan derivatives were characterized by 1 H NMR and IR spectroscopy. The polymers are highly soluble in a wide pH range, which opens new perspectives for the applications of chitosan-based materials.

Water-soluble peptide-chitosans were obtained by reaction of low-molecular-weight chitosan, having a low degree of acetylation, with peptide substituents under mild conditions. These peptide substituents were prepared by standard peptide chemistry from 3-bromopropanoic acid and tert -butyl esters of the α-amino acids glycine and phenylalanine. The structure of the new peptide-chitosan polymers was confirmed by proton nuclear magnetic resonance and infrared spectroscopy. The thermotropic and morphological properties of both the new peptide-chitosans and two other analogues, derived from valine and aspartic acid [synthesis reported in Batista, M. K. S., Pinto, L. F., Gomes, C. A. R., & Gomes, P. (2006). Novel highly soluble peptide-chitosan polymers: Synthesis and spectral characterization. Carbohydrate Polymers, 64 , 299–305], were evaluated by differential scanning calorimetry and scanning electron microscopy, respectively. As compared to the parent unmodified chitosan, the four peptide-chitosans had higher thermosensitivity, porosity and water-holding capacity, and such effects increased with the hydrophilicity of the peptide ligands. The acid-base properties of the four peptide-chitosans were also evaluated by potentiometric techniques and reflected the influence of the inserted ligands on the polymers’ acidity constants. It was also possible to confirm the polymers’ solubility over the 2–10 pH range. Overall, these polymers present physico-chemical properties that make them promising candidates for the design of novel drug delivery systems.

This work reviews the application of various standard isotherms to evaluate the micropore volume in a range of microporous materials. The selected materials have quite different surface chemistry, and are relevant due to their properties for adsorption and catalysis: zeolites, activated carbons, clay-based materials and MOFs. Some cases were analysed before and after being used as supports in the heterogenization of homogeneous catalysts. The discussion is centred, but not limited, to the three standard isotherms that are mostly employed in the literature (t-curve, non-porous carbon and non-porous hydroxylated silica) for the assessment of the micropore volume. For a given material the values of the micropore volumes from the different standard isotherms were compared, particularly against the values from the largely used t-curve. The cases where major discrepancies were found could normally be ascribed to samples that have a broad micropore size distribution.

Turning waste into valuable products: K ₂ CO ₃ activation of rapeseed residues from biodiesel industry for the production of new and reusable activated carbons for caffeine removal from water.