SURFACE MONOLAYERS OF WELL-DEFINED AMPHIPHILIC BLOCK COPOLYMER COMPOSED OF POLY(ACRYLIC ACID) OR POLY(OXYETHYLENE) AND POLY(STYRENE) .1. INTERPOLYMER COMPLEXATION AT THE AIR-WATER-INTERFACE

Amphiphilic block polymers (2, 3) composed of poly(acrylic acid) (PAA) or poly(oxyethylene) (POE) and chain length controlled poly(styrene) (PSt) have been prepared by using a catalytic system of tri-bromomethyl-terminated oligomer and manganese carbonyl. All the amphiphilic materials formed well-behaved surface monolayers, and the II-A curves for them expanded systematically with an increase of the PSt chain length. The monolayers for 2 were considerably affected by varying the pH in the subphase, due to a conformational change of the PAA segment. Interpolymer complexes between 2 or 3 and poly(vinylpyrrolidone) or PAA in the subphase, respectively, were formed at the air-water interface at an appropriate pH value. In the case of 3-PAA complexed monolayers, the limiting area was markedly expanded below pH 5, which corresponds to the apparent dissociation constant (pKJ of PAA, suggesting a formation of interpolymer complex. Above pH 5, the limiting area was close to that on water (in the absence of PAA) due to the suppression of such complexation by the ionization of the carboxy-lic acid groups. Such interpolymer complexation was also reversibly controllable at the air-water interface by varying the pH in the subphase. © 1990, American Chemical Society. All rights reserved.