Langmuir, Vol.14, No.22, 6448-6456, 1998
Monolayer formation of hydrophobically modified maleic anhydride and maleic acid copolymers on various subphases
The formation and transfer of ordered layers of poly(maleic anhydride-alt-alkyl vinyl ether)s and poly(maleic acid-alt-alkyl vinyl ether)s with and without (cyanobiphenylyl)oxy moieties on aqueous subphases is studied by use of the Langmuir-Blodgett technique. The length of the spacers, flexibility of the polyelectrolyte backbone, pH of the subphase, and the presence of counterions determine the orientation of the polymers at the air-water interface. As counterions Cu2+, Mg2+, tetrabutylammonium, n-dodecyltrimethylammonium, and n-dodecyl sulfate are used. The increase in lift-off area proves the interaction of both cationic and anionic surfactants with the maleic acid copolymers. This is due to electrostatic interactions between the charged groups and hydrophobic interactions between the side chains of the polymer and surfactant tail. The pi-A isotherms and Brewster angle microscopy of the maleic acid copolymers on water and on a 1 mM n-dodecyltrimethylammonium solution show the formation of a triple layer upon compression of the monolayer. Monolayers of the maleic acid copolymers on both subphases could be transferred onto hydrophilic glass and quartz slides in a Z-type fashion. However, second harmonic generation (SHG) measurements showed that the noncentrosymmetry is not maintained in the deposited multilayers.
Keywords:LANGMUIR-BLODGETT-FILMS;AIR-WATER-INTERFACE;PREFORMEDPOLYMERS;POLYELECTROLYTES;AMPHIPHILES;BEHAVIOR