Ordering of Poly(ethylene oxide)/Poly(propylene oxide) Triblock Copolymers in Condensed Films

• Published in: Langmuir Vol. 15; no. 7; pp. 2580 - 2585
• Main Authors: O'Connor, Stephen M, Gehrke, Stevin H, Retzinger, Gregory S
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 30-03-1999
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Surface properties; Monolayer; Compressibility; Property composition relationship; Liquid solid adsorption; Non ionic surfactant; Surfactant polymer; Air water interface; Ethylene oxide copolymer; Experimental study; Layer thickness; Spherical interface; Triblock copolymer; Adsorbed layers; Morphology; Structural model; Propylene oxide copolymer
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la9811113

Triblock copolymers of the form PEOαPPOβPEOα [where PEO is poly(ethylene oxide) and PPO is poly(propylene oxide)] form stable insoluble monolayers at both the air−water and solid−water interfaces. At the air−water interface, the nominal equilibrium spreading area of copolymers that have the same PPO content, or “core”, increases with increasing PEO content by an amount equivalent to the area of the hydrated ethylene ether subunits. With compression, a PEO-dependent transition from an expanded to a more condensed monolayer occurs at ∼10 dyn·cm-1, presumably because of condensation of PEO segments onto the core and out of the plane of the surface. Consistent with these results and interpretation, the thickness of adsorbed films of copolymers from series that have fixed cores increases approximately linearly with ethylene oxide content. At collapse of copolymer films, the nominal area per moleculeregardless of the number of ether functions in the PEO segmentis that of the hydrated PPO core. On the basis of these data, we propose models for the structure and ordering of triblock copolymers in condensed films, and we relate these models to the gradation in protein resistance observed for such films.