Organic-inorganic hybrids containing B_2O_3

摘要

Hybrid organic-inorganic polymers containing different borate compounds have been synthesised by the sol-gel method. As precursors, LiOCH_3, H_3BO_3, B(OCH_3)_3, Na_2B_4O_7. 10H_2O and polyvinyl alcohol (PVA) are used. The phase formation and structural changes are established by infrared spectroscopy and x-ray diffraction. The hybrids obtained are transparent and flexible up to 180 deg C By heat treatment up to 300 deg C it is possible to obtain glass like bulk materials or coatings. Above this temperature the samples gradually transform into powders which are in an amorphous or crystalline state depending on composition. It is established that the simultaneous participation of Li_2O and Na_2O leads to the formation of a transparent glass after melting at 850 deg C without any crystalline inclusions. It is assumed that the network of the gels and the glass is built from complex structural units formed by BO_3 and BO_4 groups in different ratios depending on the composition. The BO_4 groups are predominant in the structure of the gels containing both Li_2O and Na_2O.