Organic-inorganic hybrid glasses were obtained by the sol-gel method using
as starting materials tetraethoxysilane (TEOS) and the gel modifier, dietho
xydimethylsilane (DEDMS). The effect of various molar ratios of DEDMS and T
EOS on the quality of gels has been determined. It has been found that tran
sparent gels can be obtained only at the molar ratio DEDMS:TEOS less than o
r equal to1. To determine the effect of DEDMS addition on the structure and
microstructure of silica gel derived from TEOS, FTIR spectra of gels were
measured and the porous structure was examined. From FTIR data it follows t
hat DEDMS accelerates polycondensation reaction already at 40 degreesC; the
evidence of it is the loss of the band at 950 cm(-1) characteristic for Si
-OH groups in the spectra of gels modified by DEDMS. The examinations of po
rous structure of gels showed that DEDMS causes some reduction of the speci
fic surface area of gels and small increase of the dimensions of pores. The
organic dye (2 ' ,7 ' dichlorofluorescein) was introduced into both, silic
a gel and organically modified (DEDMS) silica gel. The optical absorption i
n the ultra-violet and visible wavelengths of hybrid glasses as well as the
thermal stability of colour up to 200 degreesC were determined. The colour
derived from the 2 ' ,7 ' dichlorofluorescein depended in the first place
on the thermal treatment parameters and was stable to 100 degreesC; heating
of gels to 200 degreesC reduced the colour intensity. Any effect of DEDMS
addition on the optical absorption of gels containing organic dye was not o
bserved. (C) 2001 Elsevier Science B.V. All rights reserved.