Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 4, pp. 713−718.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.V. Pestov, S.Yu. Bratskaya, Yu.A. Azarova, M.I. Kodess, Yu.G. Yatluk, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84,
No. 4, pp. 678−683.
AND POLYMERIC MATERIALS
N-2-(2-Pyridyl)ethyl Chitosan: Synthesis
in Gel and Sorption Properties
A. V. Pestov
, S. Yu. Bratskaya
, Yu. A. Azarova
, M. I. Kodess
, and Yu. G. Yatluk
Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia
Institute of Chemistry, Far-Eastern Branch, Russian Academy of Sciences, Vladivostok, Russia
Received June 22, 2010
Abstract—A procedure was developed for preparing a new heterocyclically substituted chelating aminopolymer,
N-2-(2-pyridyl)ethyl chitosan, by direct addition of 2-vinylpyridine to chitosan under the conditions of synthesis
in gel. The resulting polymer has the degree of substitution of up to 1. The ability of the samples obtained to sorb
transition and noble metal ions was evaluated.
Chemical modiﬁ cation of a polymeric matrix,
including natural polymers, by introduction of chelating
groups is a widely used way to enhance the capacity
and selectivity in sorption of metal ions. For example,
carboxyalkylation of chitosan, an aminopolymer known
as effective sorbent of many metal ions , yields
derivatives that exhibit higher sorption capacity and
high selectivity to certain 3d-metal ions, in particular, to
Cu(II) [2, 3]. Essential changes in sorption properties are
also ensured by modiﬁ cation of chitosan with nitrogen-
containing functional groups. It is known that grafting
of low-molecular-weight polyethylenimine to chitosan
leads to a considerable increase in the sorption capacity
ions , and dimethylaminoethylation of chitin
allows preparation of a polymer that can coordinate the
cluster used as reduction catalyst . Covalent
linking of aza crown ethers to chitosan molecule enhances
the selectivity of the sorption of Hg
 and Ag
ions. Preparation of a chitosan derivative containing
2-pyridyl substituent [N-(2-pyridyl)methyl chitosan,
PMC] is considered as one more way to enhance the
capacity and selectivity in sorption of Cu(II) ions .
Indeed, the formation of a ﬁ ve-membered chelate ring
increases the sorption capacity of the polymer by a factor
of 3 compared to the polymer containing nonchelating
4-pyridyl group . PMC also exhibits high sorption
capacity for noble metal ions , comparable with that
of sulfur-containing chitosan derivatives .
In [8–10], heterocyclic derivatives of chitosan were
prepared by linking 2-thienyl and 2-pyridyl groups
to the chitosan amino group via methylene bridge,
using a sequence of the Schiff base formation in the
reaction with the corresponding aldehyde and the
reduction with borohydrides. Such polymeric matrices
can form with transition metal ions a ﬁ ve-membered
chelate ring. Therefore, the polymers cross-linked with
epichlorohydrin can be used as effective sorbents.
However, this route to heterocyclic chitosan
derivatives has certain drawbacks. First, the process
consists of two steps: heterylmethylidenation of chitosan
and reduction of the product obtained. Second, it
involves the use of organic solvents (methanol, dimethyl
sulfoxide) and of poorly stable and toxic hydride
reductants (sodium cyanoborohydride or borohydride).
A more efﬁ cient route of amine heterylation is direct
addition of α,β-conjugated compounds. In particular,
with 2-(2-pyridyl)ethyl group introduced into chitosan,
sorption of metal ions can be accompanied by formation
of a six-membered chelate ring, which can lead to
selective sorption of deﬁ nite kinds of ions.