Stability of Fluid Ultrathin Polymer Films in Contact with Solvent-Loaded Gels for Cultural Heritage

Abstract

The removal of ultrathin amorphous polymer films in contact with an aqueous gelled solution containing small amounts of good solvent is addressed by means of specular and off-specular neutron reflectometry. The distribution of heavy water and benzyl alcohol is revealed inside Laropal A81, often employed as a protective varnish layer for Culture Heritage in the restoration of easel paintings. The swelling kinetics, interface roughness, and film morphologies were recorded as a function of temperature and increasing benzyl alcohol concentration in the dispersion of Pemulen TR-2, a hydrophobically modified acrylic acid copolymer. The addition of small amounts of good solvent results in the appearance of water-filled cavities inside the varnish, which grow with time. It is shown that while increasing the solvent concentration greatly enhances the hole growth kinetics, an increase in temperature above the glass transition temperature does not have such a big effect on the kinetics.

Combined specular and off-specular reflectometry: elucidating the complex structure of soft buried interfaces

“…However, statistical interface roughness is often neither a unique nor a dominating source of OSS. In many cases the principle contribution to OSS is provided by other sources, such as long-range density or concentration fluctuations (Lauter et al, 2016;Lauter-Pasyuk et al, 2003), magnetic or structural micro-domains (Zabel et al, 2007), natural or artificial lateral micro-patterns (Toperverg & Zabel, 2015;Toperverg, 2015), dewetting holes (Castel et al, 2020) etc., whenever the corresponding SLD deviations from their mean value are sufficiently strong and of proper lateral and transverse dimensions. Although the DWBA approach can be readily formulated for all the cases listed above, when interpreting experimental OSS data one needs a reliable proof for the chosen model.…”

The evolution of surface structure during simulated atmospheric ageing of nano-scale coatings of an organic surfactant aerosol proxy

“…79 An increase in off-specular scattering around the critical edge has been demonstrated for a polymer film de-wetting from a surface. 80 We carried out off-specular NR measurements, showing evidence of off-specular scattering occurring around the critical edge, which increased at high humidity (see Section S9, ESI†).…”

From Nanoparticles to Gels: A Breakthrough in Art Conservation Science

“…A complementary task to consolidation and protection is the cleaning of works of art, i.e., the removal of any undesired layers from the works’ surface, including dirt/soil, contaminants, corrosion, or degradation products, as well as aged varnishes/coatings/adhesives, overpaint, and vandalism. Indeed, cleaning is one of the most recurrent restoration interventions, and the common issue to practically all cases is to achieve selective removal of the undesired layers without affecting the artifacts’ original components. , Given the complexity of surfaces and interfaces in works of art, and their frequent sensitiveness to aqueous solutions or solvents, achieving safe, selective, and time-effective cleaning is often a challenging task. − Historically, cleaning operations employed organic or biological materials, such as wine, vinegar, or bile fluids, which already contained solvents, surfactants, and colloidal soft matter. However, scientific awareness and rigorous materials design have been replacing serendipity and trial-and-error starting only in the 1980s.…”

“… 4 , 96 Given the complexity of surfaces and interfaces in works of art, and their frequent sensitiveness to aqueous solutions or solvents, achieving safe, selective, and time-effective cleaning is often a challenging task. 97 − 100 Historically, cleaning operations employed organic or biological materials, such as wine, vinegar, or bile fluids, which already contained solvents, surfactants, and colloidal soft matter. However, scientific awareness and rigorous materials design have been replacing serendipity and trial-and-error starting only in the 1980s.…”