Influence of catalyst in the synthesis of a cellulose-based sensor: Kinetic study of 3-glycidoxypropyltrimethoxysilane epoxy ring opening by Lewis acid

Hybrid halochromic sensor coatings were realized immobilizing Nitrazine Yellow (NY) onto cotton fabrics via the epoxy group of 3-glycidoxypropyltrimethoxysilane (GPTMS) silica precursor in acidic condition. Boron trifluoride diethyl etherate (BF3OEt2) in a various percentage range (1-10%, w/w GPTMS) has been used to catalyze the epoxide ring opening. In order to optimize the system, an FTIR study has been developed and kinetic data were obtained for the epoxy ring opening process. A linear correlation between the obtained kinetic rates and BF3 percentage was observed. By nuclear magnetic resonance (NMR) analysis in solution the real structure of NY, derived from an attack of diazonium salt to para hydroxyl position, was confirmed and the final product of the reaction between NY and GPTMS was characterized. Finally, the different amounts of catalyst were found to affect the coatings wash fastness and the halochromic response of the cellulose-based sensors.