Poly(monomethyl itaconate) as subphase stabilizer of maleic anhydride-alt-stearyl methacrylate monolayers at the air-water interface. The study on surface pressure-area isotherms

Alternating maleic anhydride-alt-stearyl methacrylate (MA-alt-StM) amphiphilic copolymer and poly(stearyl methacrylate) (PStM) were spread as monolayers by evaporation of chloroformic ca. 0.1% (w/v) solutions on the surfaces of water and aqueous solutions. Surface pressure (π) vs. area (A) (Ų per repeating unit) isotherms (298 K) were measured for MA-alt-StM and PStM spread on water and on aqueous poly(monomethyl itaconate) (PMMeI) solutions at pH 3.0 and 7.0. PMMeI modified considerably the shape of the MA-alt-StM-on-water isotherms. The zero-pressure limiting area per repeating unit (ru), A₀, rose from 38 to 41 Ų/ru (Table 2). At pH 3.0, the surface pressure along the MA-alt-StM isotherm on aqueous PMMeI as subphase was higher than that at pH 7.0 under otherwise identical conditions. At pH 3.0, PMMeI stabilized the MA-alt-StM monolayers, presumably via H-bonding which is believed to result in an interpolymer complex. The formation of a complex is supported in terms of Brewster angle microscopy images (Figs. 2, 3 in conjunction with Fig. 1), which showed the monolayer (supposed to contain the complex) to be more homogeneous, and by FTIR spectra (Fig. 5) which adduced evidence for the occurrence of specific interactions.