Adsorption Kinetics and Mechanical Properties of Ultrathin Polyelectrolyte Multilayers: Liquid-Supported versus Solid-Supported Films

Abstract

Multilayers of sodium salt of poly(4-styrene sulfonate) (PSS) and poly(diallyl dimethyl ammonium) chloride (PDADMAC) have been built layer by layer (LbL) both at the solid/aqueous interface (solid supported) and the air/aqueous interface (liquid supported). For the solid-supported multilayers, the adsorption kinetics and the complex shear modulus were measured using a dissipative quartz crystal microbalance and a null ellipsometer. A bubble tensiometer was used to measure the adsorption kinetics and the elasticity modulus of the liquid-supported multilayers. At the solid/aqueous interface, adsorption kinetics changes with the number of adsorbed layers. However, at the air/aqueous interface, PSS dynamics were the same for all adsorbed layers except the first. Conversely, the adsorption kinetics of PDADMAC at the air/water surface differed between those layers close to the interface and those far from it. Multilayers grow at the air/water interface by an intrinsic-charge-compensation process, whereas, for the same ionic strengths, solid-supported layers deposit by the extrinsic-charge-compensation process. No significant differences were found between the recoverable dilational storage modulus of the liquid-supported multilayers and the real part of the shear modulus of the solid-supported ones built at the same ionic strength. The values of the modulus are in the MPa range, which corresponds to gel-like films. This result is in agreement with the strong hydration degree of the LbL films calculated from ellipsometry measurements.

Racial Variations in Interfacial Behavior of Lipids Extracted From Worn Soft Contact Lenses

“…25,26 These results imply that lipid films made of samples collected from healthy Caucasian subjects have higher melting temperature than lipid films from Asian subjects. It has been reported that the phase transition temperature of human Meibum decreased by 4° C over an age range of 4 to 90 years due to age-related compositional changes in the Meibum.…”

New views on foams from protein solutions

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Adsorption of cationic polymers on the surfaces of anionic glass microspheres

“…This procedure makes it possible to impart desired functionality to the surface; to simplify purifi cation of the final product; and to covalently bind bio logically active compounds, dyes, etc., to the modified surface [3][4][5][6]. Numerous studies dealing with this problem concerned various issues, including the kinetics of adsorption of polyelectrolytes [7,8], the density of surface coverage by a polymer [9], the thick ness of the adsorption layer [10,11], the conformation of adsorbed macromolecules [12,13], the aggregative stability of colloid particles modified with polyelectro lytes [14], the competitive adsorption of polymers of various molecular masses and chemical natures [15,16], the migration of adsorbed macromolecules along the surface and between various surfaces [17], which were covered in a number of reviews and monographs (e.g., [18], [19]). …”