Langmuir and Langmuir−Blodgett Films of Multifunctional, Amphiphilic Polyethers with Cholesterol Moieties

Langmuir films of multifunctional, hydrophilic polyethers containing a hydrophobic cholesterol group (Ch) were studied by surface pressure−mean molecular area (π−mmA) measurements and Brewster angle microscopy (BAM). The polyethers were either homopolymers or diblock copolymers of linear poly(glycerol) (lPG), linear poly(glyceryl glycidyl ether) (lPGG), linear poly(ethylene glycol) (lPEG), or hyperbranched poly(glycerol) (hbPG). Surface pressure measurements revealed that the homopolymers lPG and hbPG did not stay at the water surface after spreading and solvent evaporation, in contrast to lPEG. Because of the incorporation of the Ch group in the polymer structure, stable Langmuir films were formed by Ch-lPGn, Ch-lPGGn, and Ch-hbPGn. The Ch-hbPGn, Ch-lPEGn, Ch-lPEGn-b-lPGm, Ch-lPEGn-b-lPGGm, and Ch-lPEGn-b-hbPGm systems showed an extended plateau region assigned to a phase transition involving the Ch groups. Typical hierarchically ordered morphologies of the LB films on hydrophilic substrates were observe...