CHARACTERIZATION OF POLYSTYRENE-BLOCK-POLY(4-VINYL-PYRIDINE) BLOCK-COPOLYMER MICELLES IN TOLUENE SOLUTION

Polystyrene-block-poly(4-vinylpyridine) diblock copolymer micelles of various compositions and molecular weights were characterized in tolue ne. Static light scattering, quasielastic light scattering and viscosi ty measurements were used to determine the basic micellar characterist ics (aggregation number, micellar size, geometry and polydispersity). Depending on the copolymer under investigation, two different geometri es (spherical and non-spherical geometry) were observed. The micelles which are spherical in shape have aggregation numbers in the range 200 -600 while the non-spherical micelles have a much larger aggregation n umber (ranging between 600-1000). The sizes of the micelles remain unc hanged in our concentration range (10(-3)-5 . 10(-3) g/mL) and no crit ical micelle concentration could be detected in the concentration rang e from 10(-5) to 10(-3) g/mL. A detailed analysis of the structural pa rameters of the micelles which are spherical in shape, reveals that th e core-shell interfacial area per copolymer chain as well as the volum e fraction of the copolymer in the shell are relatively constant, and that the core is almost not swollen by the solvent. Mixed uniform mice lles were observed after mixing equal amounts of two solutions contain ing micelles differing in size and molecular weight. The reequilibrati on rate was found to be very fast.