Complexes of polyelectrolyte hydrogels with organic dyes: Effect of chargedensity on the complex stability and intragel dye aggregation

The swelling behavior of polyelectrolyte gels based on poly(diallyldimethyl ammonium chloride) (copolymers of diallyldimethylammonium chloride and acry lamide with the variable composition) and poly(methacrylic acid, sodium sal t) in the presence of organic water soluble dyes (alizarin, naphthol blue b lack, rhodamine) was studied. The collapse of the polyelectrolyte gels in t he presence of oppositely charged dyes together with the effective absorpti on of dyes was observed. The shrinking degree and the dye absorption by the gel depend on the charges of the polymer network and the dye, and also on the dye concentration. Stability of the gel-dye complexes in a salt solutio n of NaCl and Al-2(SO4)(3) was studied. It was shown that the complex stabi lity in the salt solution depends on the charge density of the polymer chai ns forming the gel. The increase of charge density of polymer generally lea ds to the enhancement of the complex stability. For the systems with the fr action of charged poly(diallyldimethylammonium chloride) monomer units abov e 0.5 the release of alizarin to the external solution of Al-2(SO4)(3) rese rvoir is practically completely suppressed. The obtained results show that oppositely charged dyes are generally from stable complexes with polyelectr olyte gels. (C) 1999 John Wiley & Sons, Inc.