1070-4272/05/7801-0026C2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 1, 2005, pp. 26 !32. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1,
2005, pp. 28!35.
Original Russian Text Copyright + 2005 by Golubeva, Korytkova, Gusarov.
AND INDUSTRIAL INORGANIC CHEMISTRY
Hydrothermal Synthesis of Magnesium Silicate Montmorillonite
for Polymer!Clay Nanocomposites
O. Yu. Golubeva, E. N. Korytkova, and V. V. Gusarov
Grebenshchikov Institute for Silicate Chemistry, Russian Academy of Sciences, St. Petersburg, Russia
Received September 7, 2004
Abstract-Conditions of hydrothermal synthesis of magnesium silicate montmorillonite Mg
O with a particle size of 503100 nm are optimized, including the temperature, initial chemicals, reaction
medium, and run duration.
At present, synthesis of hybrid polymer3inorganic
nanocomposites appears to be one of the most effec-
tive ways in developing novel structural materials.
A steadily growing interest in nanocomposites is
stimulated by their improved physical and mechanical
characteristics as compared to micro- and macrocom-
posites containing the same or even larger amounts
of an inorganic filler.
Interest in polymer3inorganic nanocomposites
based on layered silicates has quickened since 1987,
when a series of works on Nylon3clay hybrids were
published by the Toyota Research Center . It was
demonstrated that small additions of layered minerals,
particularly montmorillonite, significantly enhance
the thermal resistance and mechanical characteristics
of the polymer.
Later on polymeric nanocomposites with layered
silicates as fillers were intensively studied . Poly-
mer3silicate nanocomposites were found to be char-
acterized by increased strength, thermal and chemical
resistance, and ionic conductivity and by lower ther-
mal expansion coefficient and gas permeability as
compared to the initial polymer. Several character-
istics were also improved, such as the flame propaga-
tion resistance and barrier action, which could not be
realized with any other filler . It is significant that
such improvements of properties were not accom-
panied by noticeable increase in the density or de-
crease in the light transmission .
The possibility of improvement of a series of per-
formance characteristics stimulated more extensive
applications of polymer3inorganic materials in such
areas as motor-car construction, light industry, elec-
tronics, and aerospace industry .
In the works devoted to synthesis and characteriza-
tion of polymer3inorganic nanocomposites, such poly-
mers as polyester, polyurethane, polystyrene, poly-
propylene, polyethylene, polybutadiene resin, poly-
aniline, and many others were used . However, in
all cases, practically the only material, montmorillo-
nite, representing a layered silicate, was used a filler.
Layered silicates are very convenient materials for
fabrication of nanocomposites (nanocomposite is a
composite material in which a filler dispersed in the
polymer matrix has at least one dimension of nano-
meter size). Silicate layers, being about 1 nm thick
and 10031000 nm wide, have highly developed sur-
face capable of interacting with the polymer matrix.
The particle size distribution and interaction of the
silicate layers with the polymer matrix control the per-
formance characteristics of the resulting composite.
Minerals belonging to the montmorillonite group,
in their turn (by virtue of their structural features), are
the most suitable layered silicates for nanocomposites.
Montmorillonites are natural clay minerals with the
general formula (Na, Ca, K)
, x = 0.0530.45; y = 0.0530.65. The mont-
morillonite group includes about 20 different min-
erals, among them the title mineral, montmorillonite,
being the most abundant. The crystal structure of
these minerals is characterized by layered arrangement
of cations and anions (Fig. 1). Montmorillonite stacks
have a plane of symmetry. They are faced to each
other by similarly charged oxygen layers, thus sta-
bilizing the aluminum(magnesium)3oxygen3hydroxo
layers by the van der Waals forces.
Water and other polar liquids can easily penetrate
into the interlayer space of the montmorillonite lattice,
expanding the layers to the extent depending on the