Interfacial Behavior of Poly(styrene)−Poly(ethylene oxide) Diblock Copolymer Monolayers at the Air−Water Interface. Hydrophilic Block Chain Length and Temperature Influence

Abstract

Spread monolayers of poly(styrene)-poly(ethylene oxide) diblock copolymers (PSm-PEOn, m ) 38, n ) 90, 148, 250, and 445) have been studied at the air-water interface by measuring the surface pressurearea (π-A) isotherms at several temperatures. The π-A isotherms exhibit several regions which can be ascribed to different conformations of the polymer chains: a pancake structure at low surface pressures and high areas when the isolated chains are adsorbed by both the PS globule and the PEO segments at the interface; an intermediate structure, quasi-brush, when the PEO segments are solubilized in the subphase; and finally a brush developed at low surface areas when the PEO chains are obliged to stretch away from the interface to avoid overlapping. At surface pressures near 10 mN/m there is a transition between a high-density pancake and the quasi-brush regime. The compression and the subsequent expansion curves superpose at the transition and quasi-brush regions but not at the brush and pancake stages. This points to a high cohesion in the brush structure after compression and to some irreversible entanglement and hydration of the PEO chains when immersed in the subphase. These two local hystereses depend differently on the PEO chain length and temperature. The hysteresis observed at high surface pressures (brush conformation) decreases with the PEO length and temperature, whereas the low surface pressure hysteresis (pancake) increases with PEO chain length, decreases with temperature in the range 283-298 K, and increases in the range 298-315 K. A negative mean transition entropy change was obtained from the temperature dependence of the quasi-SSAL-quasi-brush transition. The results indicate that the extensive properties of the present diblock copolymers at the interface, such as the pancake limiting area and the mean transition entropy, when expressed by PEOmer, are independent of the PEO length.

Constraining Polymers into β-Turns: Miscibility and Phase Segregation Effects in Lipid Monolayers

“…In contrast, the two-arm conjugate 7 shows a lowering of the second plateau and the appearance of a constant slope region between the plateau and the condensed state. This behavior has been previously observed for PS-PEO block copolymers and has been assigned to a quasi-brush regime in which some organization is taking place [60]. Thus, the β-turn mimetic structure should also lead to a higher organization due to the anchoring at the air-water interface.…”

Dynamic Properties of Poly(styrene)–Poly(ethylene oxide) Diblock Copolymer Films at the Air–Water Interface

“…Figure 1 shows the surface pressure isotherm of ZGH-3 determined in this work together with the data of Bijsterbosch et al (7). One can see four characteristic regions (7)(8)(9). The slow increase of the surface pressure at high areas per molecule is usually assigned to a pancake-like surface structure (a).…”

“…Since the pioneering works by Alexander (10) and de Gennes (11), many authors studied the equilibrium properties of polymer brushes theoretically using the scaling approach (12,13) or the mean field theory (7,9,(14)(15)(16)(17). The obtained conclusions were examined in a number of experimental studies at the solid-liquid (4,5) or liquid-gas interfaces (7)(8)(9)(17)(18)(19)(20)(21)(22). It is noteworthy that although the dynamic surface properties can be especially important from the point of view of applications, only a few studies were devoted to the dynamics of polymer brushes at liquid interfaces (17,20,(23)(24)(25)(26).…”

“…The surface properties are mainly determined by the interaction between the PEO blocks. At high surface pressure the formation of polymer brushes can be expected (7)(8)(9). Three experimental techniques were applied to this system: the methods of transverse and longitudinal surface waves and the oscillating barrier method.…”

Two-dimensional Self-assembly of a Designed Amphiphilic Peptide at Air/Water Interface

“…This pseudo plateau is usually observed in the selfassembly behavior of PEG homopolymer 19 and block copolymer having PEG segment. 20,21 At this surface pressure, conformation at the air/water interface is transformed from a flattened conformation in contact with water surface to a brush conformation where PEG segments are located in the water.…”