Effect of Hydrophobic Bonding on the Conformational Transition and Properties of Intramolecular Micelles Formed by Copolymers of Maleic Acid and Styrene

Abstract

Fluorescence probing has been used to study the conformational transition and the properties of the microdomains formed by copolymers of maleic acid with styrene esterified with aliphatic alcohols of variable chain length, MAS- n . The steady-state and time-resolved measurements of pyrene fluorescence show the existence of two different microdomains over the whole range of pH. The pH-induced transition modifies the structure of the intramolecular micelles, but the hydrocarbon interaction prevents the expansion of the chain to the random-coil conformation. The copolymers with octyl or longer alkyl groups do not show a conformational transition. At a low degree of neutralization a change of micellar composition, with increasing side chain length, is detected by pyrene. The quenching of pyrene fluorescence by nitromethane, thallium nitrate, and sodium iodide reveals that the environments provided by MAS- n are less rigid than in poly(methacrylic acid) and that the ionized carboxylic groups are not randomly distributed.