Interaction of nanosized copolymer networks with oppositely charged amphiphilic molecules

A new class of nanocomposite materials is synthesized by reacting nanoscale networks of cross-linked hydrophilic nonionic and cationic polymers, poly(ethylene oxide)-cl-polyethyleneimine, with anionic surfactants. Formation of hydrophobic domains from polyethyleneimine-surfactant complexes leads to a network collapse exhibited in a decrease in the particle size from ca. 300 nm to ca. 50 nm. Due to their cross-linked architecture, the poly(ethylene oxide)-cl-polyethyleneimine-based complexes are more resistant to the changes in the environmental characteristics, such as pH and salt concentration, compared to complexes formed by a graft copolymer, poly(ethylene oxide)-g-polyethyleneimine and surfactants. Poorly soluble biologically active molecules, retinoic acid and indomethacin, were immobilized in the network complexes forming stable aqueous dispersions. The release of the drug from the network dispersion has been demonstrated. These materials are potentially useful as carriers in pharmaceutical drug delivery applications.