1070-4272/05/7803-0484+2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 3, 2005, pp. 484 ! 486. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3,
2005, pp. 490! 492.
Original Russian Text Copyright + 2005 by Kulish, Gerchikov, Kolesov, Zaikov.
AND POLYMERIC MATERIALS
Supramolecular Effect in Initiated Oxidation of Polyisoprene
and Polyisoprene!Polybutadiene Blends
in Chlorobenzene Solution
E. I. Kulish, A. Ya. Gerchikov, S. V. Kolesov, and G. E. Zaikov
Bashkir State University, Ufa, Bashkortostan, Russia
Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia
Received December 9, 2004
Abstract-Specific features of initiated oxidation of polyisoprene and polyisoprene!polybutadiene blends in
chlorobenzene solution were studied in relation to the supramolecular state of the polymer in solution.
Available data  show that the mechanisms of
oxidation of low- and high-molecular-weight com-
pounds have much in common. Nevertheless, there are
certain differences associated primarily with the struc-
tural features of the polymers and their state in solu-
tion. Polymer solutions are nonuniform, and condi-
tions of diffusion of oxygen molecules into a macro-
molecular globule are different, which gives rise to
supramolecular effect in oxidation of polymers and
polymer blends in solution.
Polyisoprene (PI) and polybutadiene (PB) were
purified by double reprecipitation with ethanol from
solution in chlorobenzene (CB). Chlorobenzene was
purified as described in . The initiator, dicyclohex-
yl peroxydicarbonate (DCPDC), was recrystallized
from toluene. The polymer solution was prepared at
40oC for 4 h with inert gas bubbling. Solutions of
polymer blends were prepared by mixing the solutions
of the individual polymers of equal concentration in
the required proportion. The initiator was added just
before the kinetic experiment. The initiation rate con-
for dicyclohexyl peroxydicarbonate was taken
The rate of initiated oxidation of the polymers was
determined in a manometric unit from the oxygen
uptake. The solution in the reaction vessel was stirred
at 60oC with a magnetic stirrer (200 rpm). No appar-
ent oxidation of CB at 60oC was observed (no oxygen
uptake), which allows us to neglect the solvent oxida-
tion in the experiments on initiated oxidation of PI
and PI3PB blends in solution.
The kinetic curve of oxygen uptake with PI in CB
is linear and is independent of the liquid phase vol-
ume and of the stirring rate, which indicates that the
oxidation is kinetically controlled.
Viscometric studies of solutions of the polymers
and their blends were performed with an Ubbelohde
viscometer by the standard procedure .
The dependence of the PI oxidation rate on the PI
content in solution is plotted in Fig. 1a. As seen, with
increasing content of the polymer the oxidation rate
grows nonlinearly. A similar pattern was observed
previously in  for initiated oxidation of PE and PP
and in  for oxidation of PB in CB.
By plotting the experimental data in the ln3ln coor-
dinates, we determined the reaction order with respect
to the polymer, n = 0.32. The order with respect to the
polymer of the previously studied liquid-phase oxida-
tion of PB in CB was 0.35.
The observed trends can be explained taking into
account the structural changes occurring in the poly-
mer solution. Viscometric studies of solutions of PI in
CB, performed at the same temperature as that of the
oxidation runs, show that the transition (crossover)
from a dilute solution containing discrete macromo-
lecular globules which do not interact with each other
to a semidilute solution occurs for PI at a concentra-
(Fig. 1b). Thus, as for the previous-
ly studied PB, in a dilute polymer solution, when the
sequence of oxidation events occurs within one glob-
ule, the oxidation rate appreciably grows with an
increase in the total polymer content in the solution
(Fig. 1a, portion 1).