1070-4272/05/7807-1162C2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 7, 2005, pp. 1162!1165. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 7,
2005, pp. 1183!1186.
Original Russian Text Copyright + 2005 by Nemilov, Orlova, Chulkova.
AND POLYMERIC MATERIALS
Kinetics of Polycondensation of Betulin with Adipic Acid
V. E. Nemilov, T. V. Orlova, and Yu. S. Chulkova
St. Petersburg State University of Technology and Design, St. Petersburg, Russia
Received November 23, 2004; in final form, April 2005
Abstract-The influence of various factors on the kinetics of polycondensation of betulin (a triterpene alcohol
of the lupane series) with adipic acid was studied.
Extension of the range of polymeric binders for
composite materials involves a search for nontradi-
tional sources of monomers. One of such sources can
be by-products from processing of vegetable raw ma-
terials and from wood-chemical and wood-processing
industry. These by-products contain a large amount
of various polyfunctional organic compounds.
Of certain interest in this respect is betulin, a triter-
pene alcohol of the lupane series containing primary
and secondary hydroxy and isopropenyl groups, which
creates prerequisites for preparing linear thermoplastic
polymers . Since the isopropenyl group does not
tend to polymerize because of its structural features,
the probability of formation of branching polymers in
this case will be low. The most acceptable procedure
for polycondensation of betulin with dibasic organic
acids is polycondensation in the melt, since the agents
involved are thermally stable above the melting points
of the monomers.
Betulin was isolated from birch crust; its character-
istics were as follows: hydroxy number 253.1, iodine
number 47.6, and acid number 0, which corresponds
to 99.5% purity of the product. Adipic acid dried at
80oC met the requirements of GOST (State Standard)
When studying the kinetic features of the process,
we used the method of separate samples; to reduce the
thermal oxidative degradation, the synthesis was per-
formed in a nitrogen flow. In analysis of the kinetic
features of the polycondensation of these monomers,
it is difficult to determine with sufficient accuracy the
changes in the concentrations of primary and second-
ary hydroxy groups of betulin separately. Therefore,
we determined the overall changes in the concentra-
tion of hydroxy groups by acylation with acetic anhy-
dride in pyridine. The carboxy groups were deter-
mined by neutralization, and double bonds, by the
iodine3bromine method. It should be noted that the
concentration of double bonds remained constant in
the course of the synthesis, which confirmed the low
reactivity of the double bond in betulin. The ratio of
the hydroxy and carboxy groups remained equimolar;
therefore, the kinetic parameters determined for the
hydroxy and carboxy groups coincided.
In this study we considered the kinetic features of
polycondensation of betulin with adipic acid in a melt;
the upper limit of the polycondensation temperature is
determined by the thermal stability of betulin (265oC),
and the lower limit (215oC), by the solubility of betu-
lin in adipic acid at the equimolar reactant ratio.
The variation of the concentration of the hydroxy
groups at various temperatures is shown in Fig. 1. As
seen, the polycondensation shows no deviations; how-
ever, the plot of lnw vs. lnc (w is the reaction rate,
and c, concentration) is not a straight line but consists
Fig. 1. Concentration of OH groups c as a function of reac-
tion time t. T, oC: (1) 265, (2) 250, (3) 230, and (4) 215.