Structure and Dynamics of Pyrene-Labeled Poly(acrylic acid): Molecular Dynamics Simulation Study

An atomistic model for molecular dynamics (MD) simulations of the single chain poly(acrylic acid) (PAA), terminally substituted with two pyrene moieties, was developed. MD simulations of the structure and conformational dynamics of pyrene-labeled PAA for a varying dissociation degree (α) of the COOH group revealed that the attachment of pyrene dyes to PAA alters significantly its conformational behavior. At acidic pH (α = 0), the PAA chain collapsed into the random coil conformation, so that the two pyrene moieties formed the stable π-π stacking structure. However, at basic pH (α = 1), the PAA chain was expanded and stretched facing the pyrene dyes apart into aqueous solution.