Aggregation behavior of methacrylic acid/ethyl acrylate copolymer in dilute solutions

A co-polymer consisting of methacrylic acid (MAA) and ethyl acrylate (EA) i s commonly used as the polymer backbone for a class of hydrophobically modi fied alkaline soluble emulsion (HASE) polymer. At alkaline pH, the emulsion particle solubilizes, yielding a molecular structure that is currently not well understood. The chain conformation of a model MAA/EA copolymer (desig nated as HASE107) in 0.1 M NaCl at pH of 9 was studied by dynamic and stati c light scattering techniques. In dilute solutions, two decay modes in the distribution function are observed. These two modes (referred to as the fas t and slow modes) are attributed to the translational diffusion of the unim ers and the aggregates. In order to isolate the aggregates, the HASE107 pol ymer was dissolved in a moderately good solvent (tetrahydrofuran was chosen ), where only a single diffusion mode is observed. The results confirmed th at the copolymers synthesized via emulsion polymerization technique are blo cky, and in aqueous solutions, the blocky and more hydrophobic EA segments associate to form aggregates consisting of a few polymer chains. (C) 2000 E lsevier Science Ltd. All rights reserved.