Swelling, dewetting and breakup in thin polymer films for cultural heritage

Abstract

The removal of ultrathin amorphous polymer films in contact with nonsolvent/solvent binary mixtures is addressed by means of neutron reflectometry and atomic force microscopy.

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

“…In addition, NR can be linked to a complex sample environment like cone/plate rheology, as was done here as well. In contrast to our previous study, we cannot easily complement NR by microscopy as the gel cannot be removed from the film after application without destroying the system.…”

“…To limit the amount of aggressive solvent in the cleaning process, it was proposed to work in so-called “mild conditions” by diluting the solvent with water . However, the results preceding this work on such binary mixtures obtained by neutron reflectometry (NR) showed that above a solvent fraction of 0.3%, the water invades the whole film through a dewetting-type process, destroying the entire varnish and exposing the underlying layer to the bare liquid. On the other hand, at the beginning of the 1990s, to reduce the capillary penetration and the concentration of liquid solvents on surfaces, Wolbers suggested to increase the viscosity of the products using polymer solutions as a matrix for the cleaning agent, so-called Wolbers gels .…”

“…NR was found to be an effective technique that gives both structural and chemical information, thanks to targeted hydrogen/deuterium (H/D) labeling. It is an ideal tool to observe the solvent penetration in real-time and has already proven this in similar experiments. ,− It is a nondestructive and noninvasive technique for the investigation of thin polymer films, liquid/solid and liquid/liquid interfaces with a resolution of a few Ångströms. In addition, NR can be linked to a complex sample environment like cone/plate rheology, as was done here as well.…”

The Effect of Extraction Conditions on the Barrier and Mechanical Properties of Kefiran Films

“…The next region, 3000-2800 cm −1 , is representative of the bands attributed to the symmetric and anti-symmetric stretching modes of C-H in the methyl (CH 3 ) and methylene (CH 2 ) functional groups [35]. Additionally, the most relevant peak at 2925 cm −1 can be related to the symmetric and asymmetric stretching vibration of the aliphatic group (CH 2 ) [45]. At about 2850 and 2917 cm −1 , the bands are attributed to C-H stretching, and the peak intensity decrease is dependent on the addition of glycerol into kefiran films, which might be due to the disruption on the kefiran film's structure.…”

“…This concentration of water within the matrix of the film influences the balance between two forces that exist inside the film: extension and retraction. Therefore, the thickness of the films limits the concentration and depth of penetration of the water molecules in the polymer matrix, and also the overall swelling of the films [45]. According to the literature, the kefiran film shows very low swelling capacity.…”