CHARGE-DENSITY EFFECT OF POLYELECTROLYTE CHAINS ON THE NANOSTRUCTURESOF POLYELECTROLYTE-SURFACTANT COMPLEXES

Small-angle X-ray scattering was used to investigate the nanostructure s of complexes formed by slightly cross-linked anionic copolymer gels of poly(sodium methacrylate-co-N-isopropylacrylamide) P(MAA/NIPAM) int eracting with tetradecyltrimethylammonium bromide (TTAB), and dodecylt rimethylammonium bromide (DTAB), respectively, at room temperature (si milar to 23 degrees C). In sequence with decreasing charge density of the P(MAA/NIPAM) copolymer chains, the structures of Pm3n space group cubic, face-centered cubic close packing of spheres, and hexagonal clo se packing of spheres were respectively determined. The structural ele ments of spheres and/or rods were shown to be the spherical and/or cyl indrical micelles formed by the self-assembly of TTA or DTA cations dr iven by both electrostatic and hydrophobic interactions of the charged copolymer chains/surfactants and of the surfactants/surfactants insid e the polyelectrolyte gel matrix. Both the aggregation number and the size of the micelles decreased with decreasing charge density of the c opolymer chains. By further decreasing the charge density of the P(MAA /NIPAM) chains, the structures of resulting complexes became less orde red.