of Methylphenyldichlorosilane at Various Temperatures
A. V. Kalinin and L. V. Agibalova
Lebedev Research Institute of Synthetic Rubber, Federal State Unitary Enterprise, St. Petersburg, Russia
Received June 8, 2010
Abstract—Products of hydrolytic polycondensation of methylphenyldichlorosilane at –60 and +20°С were
studied by gel permeation chromatography.
AND POLYMERIC MATERIALS
ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 6, pp. 1052–1055. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.V. Kalinin, L.V. Agibalova, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 6, pp. 1031–1034.
Organosilicon elastomers exhibit unique properties
ensuring the capability of materials based on them to
resist external actions under extreme conditions for a
long time. The main synthetic route to this class of
polymers is anionic polymerization with ring opening
. This leads to the need for preparing and isolating
the corresponding cyclotrisiloxanes, which makes the
process considerably more expensive because of the
use of vacuum equipment and high power consump-
tion. For example, 1,3,5-trimethyl-1,3,5-tris[2-(2,2,2-
siloxane has the boiling point of approximately 220°С
at 2 mm Hg .
One of the most widely used organosilicon elasto-
mers is poly(methylphenyl)siloxane. This polymer is
used as a component of protective coatings [3–5] and
as a heat-resistant stationary phase in high-temperature
gas–liquid chromatography . Good biological com-
patibility allows its use in cosmetic  and medical 
The capability of low-molecular-weight α,ω-siloxa-
nediols formed by hydrolysis of the corresponding
dichlorosilane to undergo further condensation with
the starting dichlorosilane was reported in . This
reaction was later named hydrolytic polycondensation.
It is also indicated in  that the reaction product is a
mixture of low-molecular-weight linear siloxanes and
cyclosiloxanes, unsuitable for direct use as elastomer
or coating. It was shown previously that, when the
hydrolysis of dialkyldichlorosilane is performed
slowly in the presence of an acid stronger than H
the corresponding polydialkylsiloxane of fairly high
molecular weight is formed [10, 11]. At the same time,
at temperatures of the order of –50°С chlorosilanes
react with water at relatively high rate, though con-
siderably more slowly than at room temperature .
In this study we examined the influence of
temperature on the molecular weight of products of
Synthesis of polymethylphenylsiloxane by hyd-
rolytic polycondensation. (1) A 0.5 dm
flask equipped with a thermometer, a wide-blade stirrer
with a rubber vacuum seal, and a dropping funnel was
charged with 1 mol (191 g) of methylphenyldichloro-
silane and 0.25–0.3 g of trifluoromethanesulfonic acid.
A solution of 1 mol (18 g) of distilled water in a
double volume of tetrahydrofuran was added from a
dropping funnel over a period of 24 h with vigorous
stirring and intermittent purging with dry argon. After
adding the whole amount, the thermometer and
dropping funnel were removed and the reactor was
connected to a water-jet pump. In the course of the
subsequent 2 days, the stirring was continued at a low
rate in a vacuum. Then the mixture was neutralized
with a concentrated aqueous K
solution, and the
product was dissolved in toluene, reprecipitated with
ethanol, and dried in a vacuum (3–4 mm Hg) at 200°С.
Yield of the polymer 120 g (88% of theoretical).
(2) Equipment and reactant dosage are the same as
in experiment 1. Before starting the experiment, the