M E T H O D S

1
COVALENT CROSSLINKED COMPOSITE POLYELECTROLYTE
HYDROGEL
ECATERINA STELA DRAGAN, MARIA MARINELA PERJU
Petru Poni Institute of Macromolecular
Chemistry, Iasi, Romania, email sdragan_at_icmpp.ro
M O T I V A T I O N A N D O B J E C T I V E S

• Among the composite hydrogels, those bearing
  ionic groups occupy a special place, numerous
  contributions being focused on the preparation
  and characterization of such materials, the
  presence of ionic or ionizable centers increasing
  the number of external stimuli, which could
  support their use as smart materials 1-6
• Preparation of ionic hydrogels by covalent
  cross-linking of two polycations, one natural and
  another one synthetic, both bearing primary amine
  groups able to react with glutaraldehyde (GA) as
  cross-linking agent, was now investigated as a
  novel route to prepare composite hydrogels
• Chitosan, with a deacetilation degree of 85 has
  been used as a natural weak polycation, and
  polyN-(?-aminoethylene)acrylamide (PAEA),
  derived from polyacrylonitrile by the
  aminolysis-hydrolysis reaction, was used as a
  synthetic weak polycation
• The main parametres varied to design the
  hydrogel properties were the molar ratio between
  polycations, the ratio between the primary amine
  groups and cross-linking agent, and the total
  concentration of polycations
• The swelling degree was evaluated as a function
  of the synthesis parameters.

M A T E R I A L S
M E T H O D S

• Molar mass of chitosan was determined using the
  viscometric method. The intrinsic viscosity of
  chitosan solution in 0.3 M CH3COOH 0.2 M
  CH3COONa (11, V/V) was measured with an
  Ubbelohde viscometer at 25 oC. The viscosity
  average molecular weight of the starting chitosan
  was calculated using the equation ? 1.38 x
  10-4 MV0.85 7
• FT-IR spectra of the initial polycations and of
  their hydrogels were obtained using a Bruker
  Vertex 70 FT-IR spectrometer. Trasmission spectra
  were recorded in KBr pellets
• Swelling degree (SD) of hydrogels was calculated
  as follows
• SD (Ws - Wd)/Wd, where Ws si Wd are the
  weights of the swollen and dry samples,
  respectively.

PolyN-(?-aminoethylene) acrylamide (PAEA)
Chitosan
R E S U L T S

• Influence of cross-linker concentration on the
  properties of composite hydrogels

GA/NH2, 0.07541 HG 3
GA/NH2, 0.06051 HG 2
GA/NH2, 0.03771 HG 1
FIGURE 2 Swelling kinetics of the composite
hydrogels at 23 oC total concentration of
polycations 3.5 wt. molar ratio PAEACHI
0.7860214.
PAEA
FIGURE 3 Swelling degree as a function of the
molar ratio GA/NH2 at 23 oC total concentration
of polycations 3.5 wt. molar ratio PAEACHI
0.7860.214 the inset, swelling degree as a
function of pH.

• Swelling degree in water of the composite
  hydrogels as a function of the total
  concentration of polycations and the molar ratio
  PAEA CHI

CHI 1
FIGURE 1 FT-IR spectra of the initial
polycations and of their hydrogels.

R E F E R E N C E S
C O N C L U S I O N S
1. T. Wang, M. Turhan, S. Gunasekaran, Polym.
Int. 2004, 53, 911-918. 2. K.- F. Lin, C.- Y.
Hsu, T.- S. Huang, W.-Y Chiu, Y.- H. Lee, T.- H.
Young J. Appl. Polym. Sci., 2005, 98, 2042 -
2047. 3. J. Berger, M. Reist, J. M. Mayer, O.
Felt, N. A. Peppas, R. Gurny Eur. J. Pharm.
Biopharm., 2004, 57,19 - 34. 4. H.- S. Tsai, Y.-
Z. Wang Polym. Bull., 2008, 60, 103 - 113. 5. K.
De. Yao, T. Peng, H. B. Feng, Y, Y. He J. Polym.
Sci Part A Polym. Chem., 1994, 32, 1213 -
1223. 6. M. Y. Abdelaal, E. A. Abdel- Razik, E.
M. Abdel-Bary, I. M. El- Sherbiny J. Appl. Polym.
Sci., 2007, 103, 2864 -2874. 7. A. I. Gamzazade,
V. M. Shimac, A. M. Skljar, E. V. Stykova, S. A.
Pavlova, S. V. Rogozin Acta Polymerica, 1985, 36,
420 - 424.

• The swelling degree in water decreased as the
  content of the cross-linking agent increased, as
  expected
• The increase of the synthetic polycation
  content (PAEA) in the initial polycation mixture
  led to the increase of the swelling degree, PAEA
  being hydrophylic in the whole range of pH
• A lower total concentration of polycations led
  to a higher swelling degree in water at pH
  6.5-7, the swelling at pH 2 being almost constant.