EFFECTS OF SUBPHASE PH ON SURFACE PRESSURE AREA ISOTHERMS AND MONOLAYER DEPOSITION OF PREFORMED POLYMERS WITH ACID AND ESTER HYDROPHILIC GROUPS

The effects of subphase pH on the surface pressure-area isotherms, Langmuir-Blodgett deposition efficiency onto silicon and ionization of monolayers of derivatives of preformed alpha-olefin-maleic anhydride copolymers have been investigated. These materials contained either solely carboxylic acid or a mixture of acid and ester hydrophilic groups. The area per repeat unit of these polymer materials is insensitive to pH and is not significantly different for the di-acid and acid-ester materials. The collapse pressures decrease with increasing pH. For both the di-acid and acid-ester polymers, deposition on silicon occurs on both the in- and out-strokes for pH values lower than approximately 7.5. At higher pH values deposition is observed for out-strokes but the monolayer transferred is returned to the water surface on subsequent instrokes. The ionization of deposited multilayers of the di-acid and acid-ester polymers occurs with an apparent pK(a) of approximately 8-8.5. With the exception of the variation of collapse pressure with pH, the behaviour of these polymeric monolayers is generally similar to that found for low molar mass carboxylic acids.