Studies of interactions between silane coupling agents and cellulose fibers with liquid and solid-state NMR

The hydrolysis of three alkoxy-silane coupling agents, gamma-methacryloxypropyl trimethoxy silane (MPS), gamma-aminopropyl triethoxy silane (APS), and gamma-diethylenetriaminopropyl trimethoxy silane (TAS), was carried out in ethanol/water solutions (80/20 w/w) at different pH values and followed by H-1, C-13 and 21 Si NMR spectroscopy. Acidic media were found to stabilize the hydrolyzed forms. As expected, the formation of silanol groups was followed by their self-condensation to generate oligomeric structures, yielding, ultimately, solid homopolycondensated structures, as analyzed by Si-29 and C-13 high-resolution solid-state NMR. Hydrolyzed MPS in acidic media was then successfully adsorbed onto a cellulose surface and the ensuing substrates submitted to thermal treatment at 110-120 degrees C under reduced pressure, in order to create covalent bonds between cellulose and the coupling agent. Copyright (C) 2007 John Wiley & Sons, Ltd.