NMR Characterization of Sol-Gel derived Hybrid Nanonmaterials: insight on organic-inorganic Interfaces

This thesis is focused on the synthesis and structural characterization of hybrid Organic-Inorganic materials with different application fields (materials for VOC sensing and for polymer–based nanocomposites), exploiting the conventional sol-gel method or the Nano Building Block (NBBs) approach with the in situ water production route. In the first part of the work the co-condensation of TEOS and organofunctional alkoxysilanes allowed preparation of Hybrid Sol-Gel Networks The synergic use of XRD with NMR allowed to study in deep the phase interaction. The hybrid coatings, prepared by dip-coating technique demonstrated similarity in structural features with the bulk xerogels. Two different approaches were combined to study the coatings sorption ability towards selected Volatile Organic Compounds (VOC). The coatings appeared promising in the field of detection and removal of VOCs at low temperatures, possessing the ability to quickly desorb entrapped volatiles. Fine adjustments of such hybrids can allow to discriminate between similar compounds and decrease the water sorption phenomenon, since not only the microstructure, but the polarity of the effective hybrid coatings surface plays decisive role in sorption process. In the second part of the work the synthesis parameters were fine-tuned in order to obtain Si-based SH–functionalized NBBs. The water provided in-situ through the esterification reaction of chloroacetic acid and 1-propanol enabled the hydrolysis-condensation of –SH functionalized alkoxysilane. The choice of exploited catalyst (TFA or DBTL) and esterification reaction parameters variations clearly ruled out the preferences in NBBs structural units formation. Varying the reaction temperature conditions allowed to follow the kinetics of esterification reaction and relate the water production rate to the kinetics of NBBs growth, highlighting strong correlation of H2O availability to condensation extent. The complementary exploitation of multi-nuclear NMR, FTIR and GPC techniques elucidated in full complexity the NBBs structural features development during the reaction.