Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 2, pp. 324−326.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © V.V. Semenov, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 2, pp. 338−340.
Photolytic Procedure for Introducing
an Unsaturated Group in Polydimethyl Siloxane
V. V. Semenov
Razuvaev Institute of Organometallic Compounds, Russian Academy of Sciences, Nizhni Novgorod, Russia
Received November 14, 2011
Abstract—A procedure for introducing an unsaturated group in polydimethyl siloxane consisting in irradiating
its solution in hexane by UV light in the presence of phenylethinylpentamethyldisilane was proposed.
Photochemical reactions of oligoorganosilanes involv-
ing formation of reactive silicon particles can be used for
introducing functional groups in a molecule of liquid sili-
cone rubber [1, 2]. It is known from the photochemistry of
such compounds  that the irradiation of ethinyldisilanes
by UV light results in the formation of silacycloprenes.
Such species are highly active and readily react with
oxygen, moisture, alcohols, and ketones . The photo-
decomposition of phenylethinylpentamethyldisilane (I) in
the medium of liquid polydimethylsiloxane (PMS) should
involve the addition of a silanol end of a PMS molecule
to silacyclopropene with cycle disclosing:
As a result an unsaturated group necessary to perform
a vulcanizing process through the hydrosilylation reaction
in the presence of a hydride component and the Speyer’s
catalyst will be introduced into a terminal position of
a rubber molecule.
Phenylethinylpentamethyldisilane was synthesized
from pentamethylchlorodisilane Me
phenylethinylmagnesium bromide PhC≡CMgBr in a THF
medium. Polydimethyl silicone with hydroxyl terminal
H and viscosity of 3000 cSt was
obtained by the anion polymerization of octamethylcyclo-
(PMHS) was synthesized by the cation polymerization
of methylhydrocyclosiloxanes (Me
obtained by the co-hydrolysis of a Me
mixture in the molar relationship 2 : 1. Con-
centrated sulfuric acid taken in the amount of 1.5 wt %
of the weight of cyclosiloxanes was used as a catalyst.
According to a volumetric determination , PMHS
contained 0.45 wt % of hydrogen in ≡Si–H groups.
A solution of compound I and PMS in hexane was
irradiated by the full light of a DRT-240 mercury lamp.
After removal of hexane in vacuum liquid polydimeth-
ylsiloxane (PMSP) of yellow-green color was obtained.