On the Complex Formation in Polyelectrolyte Nanogel Systems

This paper aims to show aspects of complex formation in the polyelectrolyte nanogel system. Two sorts of systems, a polyanion (PA) and a cationic nanogel (CG) as well as an anionic nanogel (AG) and CG, were employed and studied mainly in the absence of simple salts by a combination of dynamic and static light scattering techniques. The main results are summarized as: (i) An intra-particle CG complex of PA forms via charge neutralization which follows a 1:1 stoichiometry; but (ii) the bound PA dissociates from the complex upon addition of CG, polycation or KC1, meaning that the polyelectrolyte exchange reaction takes place. (iii) The complexation upon addition of AG to CG whose charge number is grater than that of AG follows 'random model' in which the added AG uniformly binds to all of CG via a strong electrostatic attraction, whereas (iv) the addition of CG to AG results in a complex according to 'all-or-none model' in which a part of AG preferably binds to the added CG to neutralize its charges, but the other part is uncomplexed and remaining in the system. These can be understood by considering that the nanogels consist of cross-linked polyions and have the obscure sur連 絡 者:国 府 田 悦 男 E-mail:kokufuta@sakura.cc.tsukuba.ac.jp