Real-Time Monitoring of a Sol-Gel Reaction for Polysilane Production Using Inline NIR Spectroscopy

The sol-gel process is an effective method forthe preparationof homogeneous structured nanomaterials whose physico-chemical propertiesstrongly depend on the experimental conditions applied. The controlof a three-component reaction with silanes showing multiple reactionsites revealed the need for an analytical tool that allows a rapidresponse to ongoing transformations in the reaction mixture. Herein,we describe the implementation of near-infrared (NIR) spectroscopybased on compact, mechanically robust, and cost-efficient micro-optomechanicalsystem technology in the sol-gel process of three silanes witha total of nine reaction sites. The NIR-spectroscopically controlledreaction yields a long-time stable product with reproducible quality,fulfilling the demanding requirements for further use in coating processes. H-1 nuclear magnetic resonance measurements are used as referencevalues for the calibration of a partial least squares (PLS) regressionmodel. The precise prediction of the desired parameters from collectedNIR spectroscopy data acquired during the sol-gel reactionproves the applicability of the calibrated PLS regression model. Thedetermined shelf-life and further processing tests verify the highquality of the sol-gel and the produced highly cross-linkedpolysilane.