Self-Assembly Behaviors of a Well-Defined Amphiphilic Brush Polymer at the Air-Water Interface

Self-assembly characteristics of a well-defined brush polymer, poly(oxy(n-dodecyl-thiomethyl)ethylene) were in detail investigated at the air-water interface with surface-area isotherm, X-ray reflectivity, and infrared spectroscopy analyses. The brush polymer self-assembled at the air-water interface as a fully-extended chain via favorable lateral packing of the bristles in a fully extended conformation, forming highly ordered, oriented Langmuir monolayer. This well-ordered monolayer was produced via a five-regime structure formation with varying surface pressure. A Langmuir monolayer film with <= 1.92 nm thick was formed in the low surface pressure regime <= 18 mN/m and then converted to a highly dense, ordered monolayer with 3.65 nm thick in the high surface pressure regime >= 35 mN/m through monolayer-to-bilayer transition and bilayer-to-monolayer inversion. These Langmuir film formations and their ordering and orientation might be driven by the well-defined chemical architecture and the lateral orderings of the polymer backbones and the bristles in fully extended conformations.