ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 5, pp. 818!821. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + N.B. Valetova, L.L. Semenycheva, I.S. Il’ichev, A.N. Artemov, D.F. Grishin, 2007, published in Zhurnal Prikladnoi Khimii, 2007,
Vol. 80, No. 5, pp. 841!844.
AND POLYMERIC MATERIALS
Features of Polystyrene Synthesis in the Presence
N. B. Valetova, L. L. Semenycheva, I. S. Il’ichev, A. N. Artemov, and D. F. Grishin
Lobachevsky Institute of Chemistry, Nizhnii Novgorod State University, Nizhni Novgorod, Russia
Received October, 16, 2006; in final form, December 2006
Abstract-Features of radical polymerization of styrene in the presence of (diphenylbutadiene)tricarbonyl-
chromium were studied.
New approaches to control over the kinetic param-
eters of synthesis of polymers attract a great attention.
These methods involve formation of stable radicals
controlling chain propagation by the mechanism of
reversible inhibition directly in the polymerization
system (in situ) . Under these condition, poly-
merization is faster and the reaction temperature is
lower (50380oC) than those in the presence of stable
nitroxyl radicals introduced directly into the poly-
Metal-containing monomers including chromium
complexes can be used as chain-terminating agents
formed in situ under the conditions of radical initia-
tion . Organochromium compounds react with ini-
tiator radicals or with growing macroradicals to form
relatively stable metal-containing carbon radicals af-
fecting directly the polymerization rate and the molec-
ular weight of the polymers .
The aim of this study was to develop a procedure
of gel-free polymerization of one of the most prac-
tically important monomers, styrene, in the presence
of (diphenylbutadiene)tricarbonylchromium (DPB).
This complex can accept an initiator radical to form
in situ a relatively stable sterically hindered carbon
radical stabilized additionally by the arenetricarbonyl-
(Diphenylbutadiene)tricarbonylchromium was pre-
pared by the procedure described in . Its physico-
chemical properties were similar to the published data.
Styrene was purified by the conventional procedure
. Commercial azobis(isobutyronitrile) (AIBN) used
as an initiator was recrystallized from methanol. Di-
tert-butylperoxytriphenylantimony (DPS) was pre-
pared by the procedure described in . Triisobutyl-
boron was a commercial product. Physicochemical
properties of all the compounds used in this study
were similar to the published data.
Styrene was polymerized in temperature-controlled
evacuated ampules. The polymerization kinetics was
studied by gravimetric and thermographic methods.
To remove unchanged monomer from the polymeriza-
tion product, the polymers were precipitated with
hexane from an ethyl acetate solution under argon.
The molecular weight (MW) and molecular weight
distribution (MWD) were estimated by gel permeation
chromatography (GPC) . Chromatographic analy-
sis was performed on a Knauer liquid chromatograph
with a Linear-2 column ([Phenomenex]). An R-2301
Knauer differential refractometer was used as a de-
tector. The eluent was chloroform.
The study of the kinetics of styrene radical poly-
merization initiated by AIBN in the presence of DPA
showed that DPB substantially affected propagation
of the polymeric chain and significantly decreased
the gel effect (Fig. 1). Autocatalytic polymerization is
almost completely suppressed at a DPB concentration
of 0.3 mol %. In this case, the time dependence of the
styrene conversion is almost linear (Fig. 2, curve 2),
which is typical for controlled radical polymerization
13]. Styrene polymerization initiated by the radi-
cal initiator in the absence of the chromium complex
is characterized by the S-shaped time dependence of
the conversion (Fig. 2, curve 1), which is typical for
polymerization with gel effect. In this case the MW