Recent results concerning the behavior of stimuli-responsive self-assembling copolymer systems obtained in the Laboratory of Specialty Polymers at the Charles University in Prague (participating in the Marie Curie network POLYAMPHI) will be presented and discussed. The lecture will focus on two topics: (i) polyelctrolyte behavior of kinetically frozen polystyrene-b-poly(methacrylic acid) micelles in low ionic strength aqueous solutions at pH close to pKA and (iii) the reversible aggregation of polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) micelles in acidic solutions.
(i) We will demonstrate both by light scattering techniques and by Monte Carlo simulations that, despite a general opinion that the counterions are firmly kept in the osmotic brush, a high fraction of small ions escape from the polyelectrolyte shell under certain conditions and micelles interact electrostatically over long distances.
(ii) We will discuss the secondary aggregation of PS-PVP-PEO micelles in acidic media. We will try to prove by using a combination of a number of experimental techniques (both “benchmark-type” techniques, such as light scattering and those only little used in polymer science, such as fluorescence correlation spectroscopy and solvent relaxation technique, the principles of which will be briefly explained) that the destabilization of micellar solutions and the secondary aggregation is a result of a hindered salvation of crowded PEO chains in micellar shells.
Department of Physical and Macromolecular Chemistry, Charles University in Prague, Czech Republic