Monolayers of hydrogen-bonded polymer blends at the air-water interface: poly(vinylacetate)+poly(4-hydroxystyrene)

The surface pressure (Pi) vs surface concentration (Gamma(s),) curves of th e hydrogen-bonded polymer blend poly(vinylacetate) + poly(4-hydroxystyrene) (PVAc + P4HS) have been measured at 25 degrees C,onto a water subphase at pH = 2.0. While PVAc forms extended monolayers. and the free surface of wat er is found to be a good solvent for it, P4HS forms compressed monolayers, and the surface is a near Theta-type solvent for it. PVAc and P4HS form mis cible non-ideal monolayers until near the collapse pressure through the who le concentration range. The composition dependence of the Pi-Gamma(s) curve s is rather complex. Contrary to what might be expected, the addition of PV Ac to the blend does not reduce the rigidity of the monolayer until its wei ght fraction is larger than 0.5. The compressibility data of the P4HS-rich monolayers suggest the existence of a second maximum at high surface covera ges, a result already observed in some polysiloxanes.