Adsorption properties of oligo(fluorooxetane)-b-poly(ethylene oxide)-b-oligo(fluorooxetane) triblock copolymers at the air-water interface: comparison of hydroxyl and acetate end groups.

ABA triblock copolymers, where A is an oligo(fluorooxetane) and B is poly(ethylene oxide) (PEO), are prepared easily using an α,ω-dihydroxy PEO initiator and cationic, ring-opening polymerization of a fluorinated oxetane monomer. Terminal hydroxyl groups can be converted readily and quantitatively to acetate groups using acetic anhydride. Both types of triblock copolymers are surface active in water. The hydroxyl- and acetate-terminated triblocks exhibit differences in adsorption behavior. Both materials show similar surface tension reduction efficiencies (minimum surface tension at aggregation limit); however, the acetate-terminated triblock copolymer is much more effective (surface tension reduction at a given concentration to the aggregation limit). This behavior is explained by the influence of hydrogen bonding on adsorption properties of the hydroxyl-terminated triblock copolymer compared to the acetate-terminated version.