1070-4272/05/7803-0487+2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 3, 2005, pp. 487! 491. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3,
2005, pp. 493! 497.
Original Russian Text Copyright + 2005 by Sashina, Novoselov.
AND POLYMERIC MATERIALS
Polyelectrolyte Complexes of Fibroin with Chitosan
E. S. Sashina and N. P. Novoselov
St. Petersburg State University of Technology and Design, St. Petersburg, Russia
Received September 23, 2004
Abstract-Fibroin3chitosan polyelectrolyte complexes are studied by X-ray diffraction, IR spectroscopy, and
scanning calorimetry. Mechanical characteristics and the swellability of the blend films at various pHs are
The polysaccharide chitosan is a chitin deacetyla-
tion product exhibiting fungicidal and bactericidal
activities . Blends of chitosan with uncharged poly-
mers such as polyvinyl alcohol and polyesters, and
also polyelectrolyte complexes with carboxymethyl
cellulose, alginate, carboxymethyl chitin, and other
polyelectrolytes were studied . In these com-
plexes, chitosan behaves as a weak polymeric base
At present, polymer blends of chitosan with fibroin
are being studied. Fibroin is a weak polymeric acid
(isoelectric point at pH 4.035.0) . When mixing
dialyzed aqueous salt solutions of fibroin with chito-
san solutions in dilute acids [9, 10], pH-sensitive
polymeric complexes are formed, which can be used
in the form of films or gels as separating membranes,
microcapsules, medicinal implants, and catalysts.
In this work we studied synthesis and properties
of chitosan3fibroin blend films prepared from hexa-
In the work we used Bombyx mori silk fibroin pre-
treated to remove sericin and fatty, waxy, and mineral
compounds, and cut into short fibers 3.6 mm long and
34.6 mm in diameter. The fibers were dissolved in
aqueous 6 M LiBr at 60oC and dialyzed across a
semipermeable membrane. The dialyzed fibroin solu-
tion was dried at room temperature to obtain a film
and then allowed to stand in a vacuum at 40oC for
Chitosan was purchased from Dalwoo-Chitosan
Co. Ltd. (Korea) (degree of deacetylation 95%; mois-
ture content 7.5%; viscosity at 25oC of 2% solution in
2% acetic acid 30.8 mP).
As a solvent we used 1,1,1,3,3,3-hexafluoro-2-
propanol (HFP) from Merck (main product content
99%; bp 58oC; r
1.61531.618 g cm
The polymers were dissolved in HFP at room tem-
perature to obtain a clear solution of the desired con-
centration. The resulting solution was then vacuum-
filtered (Buchner funnel) through a glass filter no. 1.
Equimolar polymer solutions were mixed for 1 h with
continuous stirring to obtain the desired polymer
weight ratio. As a result, stable clear solutions were
Films were prepared by pouring the solutions
onto a foil, which was followed by removing the
solvent. The resulting films were 0.4 30.6 mm thick.
Some of the films were treated with methanol for
30 min and then air-dried. Mechanical characteristics
of the films were determined using an Instron tensile-
testing machine in accordance with DIN EN ISO
527-3 standard. Swelling of the films in distilled
water and buffer solutions at pH 2.0 and 4.0 was
studied gravimetrically. The films were kept in solu-
tion at room temperature for 30 min (this time was
demonstrated to be sufficient to reach the maximal
swelling). The degree of swelling Dw (%) was esti-
are the weights of the film before
and after swelling (g).
The density of the films was measured on an Accu-
Pyc 1330 V2.01 He pycnometer (the United States).
The film morphology was examined in a polarized
light using an Olympus U-SMAD-2 BX-50 JVC
microscope (magnification 0200). The infrared spectra
of the films were recorded on an IFS25 spectrometer
(Bruker). Thermal analysis was carried out on a