Stepwise collapse of monolayers of cyclolinear poly(organosiloxane)s at the air/water interface: A Brewster-angle microscopy and scanning force microscopy study

We report studies of the collapse of monolayers of cyclolinear poly(organosiloxane)s that consist of six-membered rings joined by oxygen bridges and that contain two phenyl groups per monomer unit. Surface pressure-area isotherms show that these films undergo a stepwise collapse. The organization within the films has been examined at different stages of the collapse process by Brewster-angle microscopy. Films transferred to mica by the Langmuir-Blodgett technique have been imaged by scanning force microscopy. Five fractions of an atactic polymer with molecular weights (M-W) ranging from 8900 to 85 000 and one trans-tactic polymer (M-W = 8100) have been investigated. Bilayers of the fractions with the highest M-W's appear in the form of islands but the bilayers in the other samples have the form of ribbons 50-250 nm wide.