Influence of molecular weight on stepwise collapse of Langmuir monolayers of cyclolinear polyorganosiloxanes

Stepwise Collapse of Monolayers of Cyclolinear Poly(organosiloxane)s at the Air/Water Interface: A Brewster-Angle Microscopy and Scanning Force Microscopy Study

“…Surface Pressure − Area Isotherms. Extensive isotherm studies of films of PMPhCS-6 polymers that differ in molecular weight and molecular structure have recently been reported …”

“…Their height exceeds that for fraction II by a factor of 3, but the area ratios are the same. Compression beyond the trilayer leads to a very steep stepless increase in the surface pressure, which is associated with the formation of a thick layer …”

“…In this case the phenyl substituents at the silsesquioxane silicons are located on opposite sides of the monomer ring; they are randomly oriented in the atactic polymer. Detailed surface pressure−area isotherms for this series of polymers have been reported elsewhere. , The characteristic viscosity η, weight-average molecular weight M W , and weight-average degree of polymerization x̄ n are summarized in Table . These polymers melt to a columnar liquid-crystalline phase, which undergoes a transition to an isotropic phase at higher temperature.…”

“…The present study is part of an effort to understand the mechanism of collapse and to determine the factors that affect the morphology of the multilayers formed. It has been observed in previous studies of CLPOS 19,20 that the isotherms are strongly affected by the molecular weight and molecular structure of the polymer. We have therefore undertaken BAM and SFM studies of monolayers and multilayers formed by a series of CLPOS with different molecular weights and tacticities.…”

Cyclolinear polysiloxanes. I. Synthesis and characterization

“…A thorough literature and patent search revealed that the concept of CLPS and eCLPS is not novel. Makarova and coworkers1–4 synthesized various oligomeric cyclosiloxanes with siloxane units of different lengths and aliphatic spacers between the cyclic units, and they investigated the spreading behavior and liquid‐crystal properties of these materials. These Russian authors found evidence for mesophase formation and examined the ability of these constructs to form Langmuir monolayers, which upon lateral compression formed ordered layers up to seven layers thick.…”