Interfacial behavior of poly(ethylene oxide)-b-poly(e-caprolactone) copolymers at the air-water interface

The self-assembly of Poly(ethylene oxide)-b-Poly(e-caprolactone) linear copolymers (PEO-b-PCL) was studied at the air-water interface. All the polymers have the same PEO chain length (60 repeat units) and the no. of e-caprolactone repeat units in the PCL block ranges from 11 to 35. The Langmuir monolayers were analyzed by surface pressure-mean mol. area (p-MMA) isotherms and compression-expansion hysteresis expts. The p-MMA isotherms exhibited 3 phase transitions around 6, 11 and 14mN/m. The first 2 transitions at lower pressures are thought to arise from PEO dissoln. in the water subphase whereas the higher pressure transition arises from PCL desorption and subsequent crystn. above the interface. The Langmuir-Blodgett films morphologies were also investigated by At. Force Microscopy (AFM). AFM imaging revealed formation of cryst. domains in the whole surface pressure range, suggesting that addnl. PCL crystn. takes place in the monolayer during and after transfer. [on SciFinder (R)]