Structure of Poly(ethylene oxide) Surfactant Polymers at Air−Water and Solid−Water Interfaces

Abstract

The surface active properties of novel poly(ethylene oxide) (PEO) containing surfactant polymers were investigated at the air-water and graphite-water interfaces. The surfactant polymers are comblike polymers consisting of a poly(vinylamine) backbone with 2 kDa PEO and hexanal side chains. The polymers were prepared with various grafting ratios of the two side chains. Surface pressure isotherms were obtained for spread monolayers for the range of polymer compositions. Two transitions are observed at 5 and 11 mN/m, which are interpreted as stages of desorption for the PEO side chains from the interface into the aqueous subphase. It is demonstrated that it is possible to scale the isotherms quantitatively to provide an accurate determination of the side chain composition. We characterized the adsorption process of two of the surfactant polymers at the water-graphite interface, using tapping mode atomic force microscopy (AFM). With high hexanal:PEO content (e.g., 8:1), the surfactant polymer rapidly forms a compact and complete monolayer 1.2 nm thick. At lower hexanal:PEO content (e.g., 4:1), a disordered layer is formed. After several hours, this layer rearranges into small scattered domains with banded structures. The structure of these layers is interpreted using a model of surface adsorption and the surface pressure isotherms.

Two-Dimensional Self-Assembly of Linear Poly(ethylene oxide)-b-poly(ε-caprolactone) Copolymers at the Air−Water Interface

“…The maximum in monolayer compressibility for the two low-pressure transitions (6.5 and 10.5 mN/m) decreases as the PCL chain length increases, suggesting PEOrelated phase transitions as previously observed for comb-like polymers consisting of a poly(vinyl amine) backbone with 2 kDa PEO side chains. 34 We believe that no compressibility maxima can be detected for the samples with the longest PCL segments at 6.5 (PEO 60 -b-PCL 27 and PEO 60 -b-PCL 35 ) and 10.5 mN/m (PEO 60 -b-PCL 35 ) because increasing the length of the PCL segment reduces the fractional interfacial area occupied by the PEO segment until the PEO phase transitions cannot be detected simply by surface pressure measurements. The maximum in monolayer compressibility for the high-pressure transition (13.5 mN/m) decreases as the PCL chain length decreases, suggesting a PCL-related phase transition.…”

Polymer Binding to Carbon Nanotubes in Aqueous Dispersions: Residence Time on the Nanotube Surface As Obtained by NMR Diffusometry

“…On the polymer side, it is the PPO block that determines binding as can be deduced from the finding that PEO chains adsorbed only very weakly at the graphite surface. 51 Therefore, attempts to disperse CNT by PEO of any length results in precipitation. As for Pluronics, the PEO blocks, highly soluble in water, are exploited as sterically stabilizing grafts bound to CNT by the hydrophobic PPO block.…”

Surface active properties of chitosan and its derivatives

“…It is well known that PEO has surface active properties in spite of the fact that it is highly soluble in water [47]. The hexyl group when added to chitosan will provide the hydrophobic part.…”