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

The Langmuir film formation of poly(ethylene glycol) (PEG)- and poly(methacrylo polyhedral oligomeric silsesquioxane) P(MA-POSS)-based diblock copolymers (PEG5k-b-P(MA-POSS)x) at the air/water interface is investigated. While the Langmuir film formed by the PEG5k collapses at π ≈ 8 mN m−1, the PEG5k-b-P(MA-POSS)x forms a stable film on the water surface revealing various phase transitions in surface pressure vs mean molecular area (π-mmA) isotherm—manifested by various pseudo-plateaus during compression. At higher surface coverage, the π-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.