The role of mild TEMPO–NaBr–NaClO oxidation on the wet adhesion of regenerated cellulose membranes with polyvinylamine

Abstract

X-ray Photoelectron Spectroscopy (XPS) was used to characterize the functional groups present on regenerated cellulose films after mild oxidation with TEMPO-NaBr-NaClO and the results were correlated with the adhesion forces holding together two wet cellulose films laminated with a thin (i.e. less than 10 mg/m 2 ) layer of polyvinylamine (PVAm). There was no correlation between adhesion and carboxyl content, whereas wet adhesion was proportional to the total content of aldehyde and hemiacetal groups on the cellulose. It is proposed that aldehyde groups react with neighboring cellulose chains to form hemiacetals which serve as crosslinks strengthening the cellulose surface. The hemiacetals can also be attacked by primary amines to give imine and aminal covalent linkages to the PVAm adhesive layer.

Lysozyme-Triggered Epidermal Growth Factor Release from Bacterial Cellulose Membranes Controlled by Smart Nanostructured Films

“…In addition, decreased signal intensity at 288.1 eV (from 20.8% to 16%) was obtained after the reaction . As previously noted by DiFlavio et al, oxidation caused the CO contribution (286.6 eV) to reduce—63.9% for untreated and 57.6% for oxidized samples—because of the conversion of primary alcohols to carboxylic groups. Moreover, according to Johansson and Campbell, air‐exposed surfaces are highly susceptible to contamination by carbonaceous materials at nonpredictable levels, explaining the increase at 285.0 eV (CC) from 15.1% to 21.9% after the oxidative process.…”

Surface Functionalized Nanofibrillar Cellulose (NFC) Film as a Platform for Immunoassays and Diagnostics

“…While the carboxylation of the NFC films could not be followed via XPS measurements (as reported by us and other groups [9], most probably due to the medium-dependent surface reconstruction of cellulose in dry medium [21], the EDC/NHS activation of the carboxyl groups leads to ester groups, which are XPS detectable [21,48]. Furthermore, the NHSesters formed during film activation contain nitrogen not otherwise present in unmodified or carboxylated films.…”

Surface modification of cellulose membranes

“…Since the experiment employed water as a solvent swelling might have added to the destabilisation of the inner membrane structure (water/MC: 4.82 nSw; (El Seoud et al, 2008)). A milder oxidation approach was investigated by DiFlavio et al (DiFlavio et al, 2007). They conditioned RC membranes with TEMPO/NaBr and afterwards subjected them to oxidation by sodium hypochlorite, which yielded presumably a mixture of the corresponding carboxylic, aldehyde and hemiacetal groups.…”