Aldehyde-conjugated chitosan-graphene oxide glucodynamers: Ternary cooperative assembly and controlled chemical release

Simultaneous condensation of aromatic aldehydes (ArxCHO; x = 1-4) on chitosan biopolymer (CS) affords, after water-evaporation, structurally-conjugated aryl-functionalized CS-Ar-x-f films. Similarly, cooperative assembly of two-dimensional nanometric graphene oxide (GO), aromatic aldehyde and chitosan provides transparent, flexible and crack-free aldehyde-functionalized, ternary-reinforced CS-Ar-x-GO-f nanocomposite films. Homogenous films were obtained using ortho-hydroxybenzaldehyde Ar-1 while the para-hydroxybenzaldehyde Ar-4 was prone to packing inside. Textural and mechanical properties were investigated and expectedly, significant improvement was found for CS-Ar-1-GO-f because of the great dispersion of the aromatic and the presence of the filler. The sensitivity of unsaturated C=N imine bond to hydrolysis was explored for triggering controlled release of aromatics from the as-prepared films. All of them were found to induce a time-dependent aromatic release. It has been moreover observed that the release was significantly delayed in CS-Ar-x-GO-f compared to CS-Ar-x-f, a fact attributed to the interplay of the ring with the basal and edges of graphene oxide, through pi-pi stacking and additional hydrogen bonding interactions. This finding shows that beyond the conventional wisdom using fillers for improving thermal and mechanical properties, the tiny carbon sheets can act as a regulator for aldehyde release, thereby providing a way for more controlled chemical delivery from confined nanocomposites.