Interactions of water-soluble polymers with small molecules I: Poly(2-diethylaminoethyl methacrylate)-orange II and ethyl orange systems

The interactions between poly(2-diethylaminoethyl methacrylate) (PDEAEMA) and orange II (OII) or ethyl orange (EO) have been examined in detail by measuring the transmittance and the specific conductance of the solutions. The mechanisms of flocculation and deflocculation have been investigated by changing the intrinsic viscosity, the degree of neutralization and alkyl groups of PDEAEMA or by adding NaCl, urea or alcohols. The complexation of PDEAEMA with dyes is completed at the same mole ratio but is not dependent on the molecular weight of PDEAEMA. OII molecules bind with PDEAEMA by electrostatic interactions, followed by flocculation through hydrogen bondings between hydroxyl groups on OII molecules bound. EO molecules first interact with PDEAEMA electrostatically in the same ways as OII, but flocculation occurs by hydrophobic interactions between ethyl groups on EO molecules bound. By further addition of dyes to the complex, OII or EO molecules already bound can interact with free OII or EO molecules newly added through hydrogen/hydrophobic interaction between OII or EO molecules. Deflocculation occurs by the electrostatic repulsion between anions of dyes bound, such as (PDEAEMA-OII)-hydrogen bonding-(OII-anions) or (PDEAEMA-EO)-hydrophobic bonding-(EO-anions) newly formed.