Adsorption of Poly(styrenesulfonate) to the Air Surface of Water by Neutron Reflectivity

Abstract

The adsorption of the strong polyelectrolyte polystyrene sulfonate (PSS) to the air surface of dilute aqueous solutions was investigated as a function of molecular weight and salt concentration. Detailed segment profiles of the deuterated polymer were determined by neutron reflection.Surface activity was also examined through surface tension measurements.In general, the segment profiles are composed of a thin layer (10-20t hick) of high concentration at the air surface, followed by a distinct second layer of much lower segment concentration that extends to larger depths into the liquid. The high segment density at the air sutiace is due to a strong surface attraction, arising from the low surface tension of the PSS backbone relative to the surface tension of water. At low salt concentration, the profiles tend toward a single dense layer, suggesting that the chains lie nearly flat at the interface in that limit. The adsorbed amount increases with salt concentration, with a stronger dependence for higher molecular weight chains. The adsorbed amounts at the air/water interface are higher than reported previously for PSS adsorbed onto neutral solid surfaces, consistent with the fact that the air-liquid interface provides a stronger surface attraction. While the trends of adsorbed amount and layer thickness with salt concentration and molecular weight are in good agreement with numerical self-consistent field lattice calculations, the measured bilayer profiles are rather different from the smoothly decaying theoretical profiles. The surface tensions of the PSS solutions are significantly lowered relative to those of pure salt solutions. Combining the reflectivity and surface tension measurements, an approximately linear relationship is established between the surface pressure and the PSS adsorbed amount.

pH-responsive non-surface-active/surface-active transition of weakly ionic amphiphilic diblock copolymers

“…Very stable micelle formation in the bulk solution may also be the principal origin [5,6] considering the fact that polyelectrolyte homopolymers are slightly surface active. Poly(styrene sulfonate) (PSS) homopolymer [15][16][17][18] and, recently, the random copolymer [6] of styrene and styrene sulfonate was found to be surface active, stressing the importance of micelle formation [5,6]. Before our study, there were already reports that the solutions of ionic amphiphilic block copolymers show no reduction of surface tension [19][20][21][22][23][24], and also reports of new non-surface active systems [25][26][27][28][29][30][31][32][33][34][35].…”

Interfacial Behavior of Solid- and Liquid-like Polyelectrolyte Complexes as a Function of Charge Stoichiometry

“…The adsorption at the air/water interface of individual synthetic and natural polyelectrolytes, the main components of PECs, has been fairly well documented in the literature for several decades, particularly with the sodium poly(styrene sulfonate) (PSSNa) [14][15][16][17][18][19][20][21][22][23][24]. The adsorption of PEs differs in many respects from that of neutral polymers.…”

Development and validation of HPLC-UV method for the quantitative analysis of carcinogenic organic impurities and its isomers in the sodium polystyrene sulfonate polymer

“…The possible impurities include surface-active agents [3] or inorganic salts such as Na 2 SO 4 [5]. The presence of these impurities has a strong effect on the polyelectrolyte properties like viscosity [4,[6][7][8][9][10][11], osmotic coefficiency [12][13][14][15], surface tension [16][17][18][19], etc.…”