Gelatin, a protective agent against iron gall ink corrosion?

Iron gall Inks are known to promote paper degradation, thus jeopardizing the conservation of written Heritage. This phenomenon, also called iron gall ink corrosion, is not only governed by chemical reactions occurring between ink constituents and cellulose (the main constituent of paper) but also by the penetration of ink components inside the paper. This penetration depends on the ability of water and ink soluble components to migrate inside the sheet. This latter is composed of hydrophilic cellulosic fibers (of diameter approx. 10 µm) embedded in a size that lowers water affinity and thus makes it suitable for writing. This work aims to better understand the impact of gelatin size on iron gall ink corrosion by investigating the distribution of gelatin and ink components at the scale of individual paper fibers. STXM, a nano-scale mapping technique (resolution of 30 nm) that also allows NEXAFS analysis was used for this purpose. Fe L-edge measurements enabled to map iron distribution and to locate iron(II) and iron(III) rich areas. N K-edge measurement made it possible to map gelatin distribution. C K-edge measurements allowed mapping and discrimination of cellulose, gallic acid, iron gall ink precipitate and gelatin. Three fibers were studied: an inked fiber with no size, a sized fiber that was afterwards inked and an inked fiber sprayed with gelatin (to model the impact of conservation treatments that use gelatin as a re-sizing agent). Analysis of gelatin and ink ingredients distribution inside and outside the cellulosic fiber gave some clues to account for the limiting impact of gelatin on iron gall ink corrosion.

Thermoresponsive Property of Polymer Hydrogels Induced by Copolymerization of Hydrophilic and Hydrophobic Monomers: Comprehensive Study from Monomer Sequence and Water Affinity

In order to raise the possibility of practical use of thermoresponsive hydrogels in various fields, it is imperative to achieve on-demand control of responsive behavior especially by using a simple...

Marine protected areas do not prevent marine heatwave-induced fish community structure changes in a temperate transition zone

Acute climate events like marine heatwaves have the potential to temporarily or permanently alter community structure with effects on biodiversity and ecosystem services. We aimed to quantify the magnitude and consistency of climate driven community shifts inside and outside Marine Protected Areas before and after a marine heatwave using a kelp forest fish community dataset in southern California, USA. Abundance, biomass, diversity and recruitment of warm-water affinity species during the marine heatwave were significantly greater compared with prior years yet cool-water affinity species did not show commensurate declines. Fish communities inside MPAs were not buffered from these community shifts. This result is likely because the particular species most responsible for the community response to environmental drivers, were not fisheries targets. Resource managers working to preserve biodiversity in a changing climate will need to consider additional management tools and strategies in combination with protected areas to mitigate the effect of warming on marine communities.

Stable metal–organic frameworks with low water affinity built from methyl-siloxane linkers

A new approach to the development of MOF materials with low water affinity is presented using siloxane-derived linkers. The low water affinity is conferred by the linker without the requirement of any post-synthetic processing apart from activation.

The behavior of ions in water is controlled by their water affinity

The strong, long-range electrostatic forces described by Coulomb's law disappear for ions in water, and the behavior of these ions is instead controlled by their water affinity – a weak, short-range force which arises from their charge density. This was established experimentally in the mid-1980s by size-exclusion chromatography on carefully calibrated Sephadex® G-10 (which measures the effective volume and thus the water affinity of an ion) and by neutron diffraction with isotopic substitution (which measures the density and orientation of water molecules near the diffracting ion and thus its water affinity). These conclusions have been confirmed more recently by molecular dynamics simulations, which explicitly model each individual water molecule. This surprising change in force regime occurs because the oppositely charged ions in aqueous salt solutions exist functionally as ion pairs (separated by 0, 1 or 2 water molecules) as has now been shown by dielectric relaxation spectroscopy; this cancels out the strong long-range electrostatic forces and allows the weak, short-range water affinity effects to come to the fore. This microscopic structure of aqueous salt solutions is not captured by models utilizing a macroscopic dielectric constant. Additionally, the Law of Matching Water Affinity, first described in 1997 and 2004, establishes that contact ion pair formation is controlled by water affinity and is a major determinant of the solubility of charged species since only a net neutral species can change phases.