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Surface rheology of PEO-PPO-PEO triblock copolymers at the air-water interface: Comparison of spread and adsorbed layers
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
2005 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 14, 6373-6384 p.Article in journal (Refereed) Published
Abstract [en]

The dilatational rheological properties of monolayers of poly(ethylene oxide)-poly(propylene oxide)poly(ethylene oxide)-type block copolymers at the air-water interface have been investigated by employing an oscillating ring trough method. The properties of adsorbed monolayers were compared to spread layers over a range of surface concentrations. The studied polymers were PEO26-PPO39-PEO26 (P85), PEO103-PPO40-PEO103 (F88), and PEO99-PPO65-PEO99 (F127). Thus, two of the polymers have similar PPO block size and two of them have similar PEO block size, which allows us to draw conclusions about the relationship between molecular structure and surface dilatational rheology. The dilatational properties of adsorbed monolayers were investigated as a function of time and bulk solution concentration. The time dependence was found to be rather complex, reflecting structural changes in the layer. When the dilatational modulus measured at different concentrations was replotted as a function of surface pressure, one unique master curve was obtained for each polymer. It was found that the dilatational behavior of spread (Langmuir) and adsorbed (Gibbs) monolayers of the same polymer is close to identical up to surface concentrations of approximate to 0.7 mg/m(2). At higher coverage, the properties are qualitatively alike with respect to dilatational modulus, although some differences are noticeable. Relaxation processes take place mainly within the interfacial layers by a redistribution of polymer segments. Several conformational transitions were shown to occur as the area per molecule decreased. PEO desorbs significantly from the interface at segmental areas below 20 ångstrom(2), while at higher surface coverage, we propose that segments of PPO are forced to leave the interface to form a mixed sublayer in the aqueous region.

Place, publisher, year, edition, pages
2005. Vol. 21, no 14, 6373-6384 p.
Keyword [en]
interacting chain molecules, poly(ethylene oxide), block-copolymers, propylene-oxide, ethylene-oxide, air/water interface, aqueous-solution, adsorption-kinetics, statistical-theory, phase-transition
National Category
Physical Chemistry
URN: urn:nbn:se:kth:diva-14882DOI: 10.1021/la0467584ISI: 000230248500038ScopusID: 2-s2.0-22444441319OAI: diva2:332923
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-10-11Bibliographically approved

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