1070-4272/03/7603-0442$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 3, 2003, pp. 442! 447. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 3,
2003, pp. 457! 462.
Original Russian Text Copyright + 2003 by N. Khimich, Koptelova, G. Khimich.
AND INDUSTRIAL ORGANIC CHEMISTRY
Synthesis and Structure of Nanocomposites in the Aromatic
N. N. Khimich, L. A. Koptelova, and G. N. Khimich
Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences, St. Petersburg, Russia
Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
Received July 24, 2002
Abstract-The possibility for preparing an organic3inorganic nanohybrid without chemical bonds between its
components by the sol3gel procedure was studied.
Nanocomposites are intensively studied in modern
materials science . These studies gave rise to
fundamentally new materials with peculiar optical,
nonlinear optical, ion-conductive, and other properties
Among nanocomposites known to date, we chose
organic3inorganic hybrids prepared by the sol3gel
method, which is one of the simplest, environmentally
cleanest, and most convenient procedures . To a
first approximation, this method involves (in the case
of formation of SiO
matrix) hydrolysis of tetra-
alkoxysilane with subsequent polycondensation of the
liberated silanols to form a three-dimensional network
incorporating the components added in advance.
Nanocomposites are formed owing to various inter-
facial interactions between the organic (i.e., polymers)
and inorganic (the three-dimensional network or its
fragments) components. The nanocomposites in which
the organic and inorganic components are chemically
bound are characterized by the best mechanical prop-
erties and highest heat resistance. Preparation of these
systems requires modification of the organic compo-
nent with, e.g., commercially available derivatives of
lane , (3-aminopropyl)triethoxysilane , and
3-(triethoxysilyl)propyl isocyanate .
The trialkoxysilane derivatives are cohydrolyzed
with tetraethoxysilane, which provides uniform distri-
bution of the organic component chemically bonded
with the inorganic matrix. Nanohybrids can be also
formed without special binders. In this case, the active
functional groups of the organic component (OH or
) polycondense with silanol liberated in the hy-
drolysis of tetraalkoxysilanes to form chemical bonds
between the components of the system [9, 10].
However, there are nanohybrids with the micro-
structure formed exclusively by van der Waals and
hydrophilic3hydrophobic interactions or hydrogen
bonds . To our knowledge, organic3inorganic
hybrids with the microstructure determined mainly
by physical interactions of the components have not
been prepared previously by the sol3gel procedure.
This is due to the fact that the organic components of
these systems should be sufficiently hydrophobic and
should not contain active functional groups, whereas
polar solvents such as alcohols and water are neces-
sarily used in modern sol3gel organic synthesis .
This confines the range of organic components intro-
duced into the SiO
matrix to strongly polar structures
soluble in aqueous solutions.
The systematic studies of sol3gel synthesis of
monolithic silica gel  show that this process
can be performed in low-polar nonaqueous systems.
This prevents uncontrolled phase separation (introduc-
tion of a lyophobic organic component into the lyo-
philic system) and formation of a nonuniform material
in the first steps of the sol3gel process. In this work
we studied features of formation of organic3inorganic
hybrids with the microstructure mainly determined
by van der Waals and hydrophobic3hydrophilic inter-
actions of the organic an inorganic components.
The organic component of the composite was an
ester dendrimer of the second (1) and third (2) genera-
tions with benzene groups in external layer: