Silane Meets Click Chemistry: Towards the Functionalization of Wet Bacterial Cellulose Sheets

Abstract

The modification of cellulosic materials is of great interest in materials research. Wet bacterial cellulose sheets were modified by an alkoxysilane under mild conditions to make them accessible to click chemistry derivatization. For this purpose (3-azidopropyl)triethoxysilane was grafted covalently onto the cellulosic surface. The silanized bacterial cellulose sheets were characterized comprehensively by attenuated total reflectance FTIR spectroscopy, solid-state NMR spectroscopy, thermogravimetric analysis, SEM with energy-dispersive X-ray spectroscopy, and elemental analysis. To demonstrate subsequent click chemistry functionalization, a new fluorophore based on fluorescein was synthesized and clicked to the silane-modified bacterial cellulose. The new method renders bacterial cellulose and other never-dried cellulosic materials susceptible to direct and facile functionalization in an aqueous medium without the need to work in water-free organic phases or to employ extensive protecting group chemistry and functional group interconversion.

Bacterial cellulose as a material for wound treatment: Properties and modifications. A review

“…The silane grafting approach is generally a promising tool to introduce functional groups of different kinds to the BC surface. It was demonstrated by Hettegger et al (2015), the grafting of azido-alkyl groups onto wet BC can be performed under mild, environmentally friendly conditions. The modification does not affect BC fibrillar structure; the fibrils on the surface were shown to be covered by siloxane together with 3-D polysiloxane network, providing accessibility and proper reactivity of the azide functional groups towards further click chemistry derivatization reactions.…”

Quantitative and Qualitative Analysis of Surface Modified Cellulose Utilizing TGA-MS

“…In order to enhance the interfacial adhesion, natural fibers are generally modified by physical methods such as plasma and corona discharge [9,10,11] as well as chemical treatments e.g., esterification, etherification, or oxidation [12,13,14,15,16,17,18]. A widely applied chemical method is the treatment of cellulose with silane coupling agents [19,20,21,22]. Surface silylation has an impact on the physicochemical properties of lignocellulosic fibers altering, e.g., moisture absorption, chemical resistance, thermal degradation, surface hydrophilicity, and improving the mechanical properties of cellulosic composites [23,24,25,26,27].…”

Nucleophilic substitution on silica surfaces: Comparison of the reactivity of α- versus γ-chlorosubstituted silanes in the reaction with sodium azide

“…15) In principle several pathways could lead to azido-functionalized silica surfaces: 1) the surface grafting agent (3-azidopropyl)trialkoxysilane could be synthesized prior to solgel processing from 3-chloropropyltrialkoxysilanes. 23) However, the ¡-analogue has not been reported so far and a stronger influence of the azido moiety on the phase separation process and thus on the hierarchically organized network structure is expected; 2) Solgel processes could be catalyzed by HI instead of HCl to facilitate the formation of the azido functionalized surface in the nucleophilic halide-azido exchange. In this case a strong influence on the final network structure can be expected as has been shown recently by using HBr or HNO 3 as the solgel catalyst.…”