Tailorable Polyanion Diffusion Coefficient in LbL Films: The Role of Polycation Molecular Weight and Polymer Conformation

Abstract

Assembly of oppositely charged macromolecules (proteins, DNA, polyelectrolytes) is often used for surface modification and functionalization. Yet, it remains a challenge to control the position and mobility of the molecules within the assembly. Using polyelectrolyte multilayers as model systems, we study the diffusion constant of the polyanion PSS. D PSS could be varied by 5 orders of magnitude. Two parameters were found to be important: (i) the conformation of the polyelectrolytes and (ii) the molecular weight of the polycation (M w(PDADMA)); the latter was the dominant parameter. Independent of conformation, by increasing M w(PDADMA), D PSS decreased by at least 3 orders of magnitude when M w(PDADMA) increased by a factor of seven. The decrease was stronger than predicted by any scaling law; it was either exponential or abrupt after D PSS was almost constant for low M w(PDADMA). The polymer conformation was adjusted with the salt concentration in the preparation solution. Flatter and less entangled chains led to an increase in D PSS. These findings on the time dependence of the internal structure of assemblies are discussed in the context of network theory.

Protective Role of Sphingomyelin in Eye Lens Cell Membrane Model against Oxidative Stress

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