Interfacial and monolayer properties of poly(vinylcaprolactam)

The surface properties of a polydisperse poly(vinycaprolactam) (48 kDa) hav e been studied at the air/water and hexane/water interfaces. Adsorption of the polymer at both interfaces shows substantial time-dependent surface ten sion lowering at remarkably low concentrations in the aqueous phase. This a dsorption is increased by addition of electrolyte, which also lowers the lo wer consolute temperature (LCT) of the polymer in solution. Adsorption is e ndothermic, corresponding with the approach to the LCT as the temperature i s raised. Spreading of the polymer at the air/water interface from aqueous solutions is near quantitative. The surface pressure-area isotherms indicat e extensive coiling in the monolayer at low pressures and looping of the po lymer monolayer into the aqueous phase in the higher pressure range.