Interpolyelectrolyte Complexes with a Micellar Structure

Abstract

We studied the properties and determined the molecular characteristics of the IPECs formed by polystyrene- block -poly( N -ethyl-4-vinylpyridinium bromide) (PS-b-PEVP) micelles and poly(methacrylic acid) (PMAA) upon mere mixing of dilute aqueous solutions of the components. The study demonstrated the self-assembling of stable water-soluble colloid nanoparticles whose shape and size are unambiguously determined by the core parameters of the initial block copolymer micelle, while the sign of the charge is dictated by the ratio of the complex-forming components. The PS-b-PEVP used in the study was synthesized by a known procedure [7] and had the following weight-average degrees of polymerization ( P w ) of the blocks: PS, 100; PEVP, 200. The polydispersity coefficient was 1.12. The PMAA fraction with P w = 2300 was used. A part of this fraction (PMAA*) was modified by introducing covalently bonded pyrenyl groups (one group per 420 monomer units) as UV-absorbing labels [8]. The PEVP homopolymer ( P w = 480) and the IPECs it forms with PMAA were used for comparison. Aqueous solutions of PS-b-PEVP were prepared as follows. First, the copolymer was dissolved in a mixed organic solvent (80 vol % DMF + 20 vol % methanol). The resulting solution was dialyzed against a large amount of water [7]. The {PMAA/PS-b-PEVP} IPEC was prepared by mere mixing of the aqueous solutions of the components taken in appropriate molar ratios. Potentiometric titration, UV spectroscopy, and dynamic and static light scattering were used in the study.