2-Dimensional surface properties of ω-methoxy poly (ethylene glycol) macromonomer and homopolymer at the air-water interface

Abstract

Two-dimensional surface properties of the macromonomer have been investigated using a Langmuir Film Balance. The macromonomer forms an expanded film, similar to hydrophilic polymers, with a maximum limiting area (A₀) of 8.75 Ų molecule^-1 at 25°C that probably arises from the more expanded conformation. The macromonomer undergoes a transition, causing a change of orientation at the interface, in the pressure region 2-6.5 mN m^-1, corresponding to respective areas of 8.4 and 5.5 Ų molecule^-1. The polymerization reaction of the macromonomer promotes hydrophobic behaviour indicated by a large collapse pressure, π_c (10 mN m^-1) and maximum surface pressure, π (16 mN m^-1) in homopolymeric film. Monolayer studies also suggest that the size of the homopolymer is 41-48 times larger than that of the macromonomer at the air-water interface.