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.