<![CDATA[<b>Formation of dense cellulose monolayers on silver surfaces</b>]]>

Abstract

A adsorção do derivado de celulose, 6-O-(2,3-bis(tiosulfato)propil-oxi-2-hidroxi-propil)-celulose (TSHP), sobre superfícies de prata foi investigada por meio de elipsometria, medidas de ângulo de contato e de espectroscopia de fotoelétrons usando fonte de raios-X (XPS). Os resultados mostraram que a formação de uma densa monocamada de TSHP sobre prata é um processo irreversível, porém lento. A partir dos resultados de XPS foi proposto um modelo para explicar quimissorção de TSHP sobre prata, no qual os grupos tiosulfato sofrem clivagem homolítica, com formação de radicais livres de enxofre. Estes ligam-se covalentemente à superfície de prata, formando uma monocamada estável de TSHP. The adsorption of a new cellulose derivative, 6-O-(2,3-bis(thiosulfato)propyl-oxy-2-hydroxypropyl)-cellulose (TSHP), onto silver surfaces was investigated by means of ellipsometry, contact angle measurements and X-ray photoelectron spectroscopy (XPS). The results showed that the formation of a dense TSHP monolayer on silver surfaces is an irreversible and slow process. Based on XPS results a model was proposed to explain the chemisorption of TSHP on silver substrates. This model considers the homolytical cleavage of the thiosulfate groups attached to the cellulose chains with the formation of thio radicals, which bind covalently to the silver surface. The formation of silver thiolates lead to a stable TSHP monolayer on silver surfaces.

Humidity Response of Cellulose Thin Films

“…The first interesting finding was that the very interface between the substrate and the cellulose “bulk” layer is rather different to the bulk layer. Although some functionalized cellulose derivatives have been exploited for monolayer formation, − there are only a few studies available which have attempted the generation of neat cellulose monolayers. For these cases, either submonolayers, fractal structures, or open films have been realized. , Therefore, the exact nature of such interfaces and their importance for film formation still remains hardly accessible.…”