Langmuir film formation of amphiphilic hybrid block copolymers based on poly(ethylene glycol) and poly(methacrylo polyhedral oligomeric silsesquioxane)

摘要

The Langmuir film formation of poly(ethylene glycol) (PEG)- and poly(methacrylo polyhedral oligomeric silsesquioxane) P(MA-POSS)-based diblock copolymers (PEG(5k)-b-P(MA-POSS)(x)) at the air/water interface is investigated. While the Langmuir film formed by the PEG(5k) collapses at pi approximate to 8 mN m(-1), the PEG(5k)-b-P(MA-POSS)(x) forms a stable film on the water surface revealing various phase transitions in surface pressure vs mean molecular area (pi-mmA) isotherm-manifested by various pseudo-plateaus during compression. At higher surface coverage, the pi-mmA isotherm exhibits a phase transition that is attributed to the transformation of the P(MA-POSS) monolayer into a multilayer film that is confirmed by AFM measurements of the Langmuir-Blodgett films fabricated before and after the phase transition and direct infrared reflection absorption spectroscopy of the Langmuir film during compression. At a still higher surface pressure, another pseudo-plateau is observed that is assigned to the ultimate film collapse as verified by the Brewster angle microscopy.