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(organos iloxane)s that consist of six-membered rings joined by oxygen bridges and t hat contain two phenyl groups per monomer unit. Surface pressure-area isoth erms show that these films undergo a stepwise collapse. The organization wi thin the films has been examined at different stages of the collapse proces s by Brewster-angle microscopy. Films transferred to mica by the Langmuir-B lodgett technique have been imaged by scanning force microscopy. Five fract ions of an atactic polymer with molecular weights (M-W) ranging from 8900 t o 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 isla nds but the bilayers in the other samples have the form of ribbons 50-250 n m wide.