Abstract
Comicellization kinetics of binary mixtures of poly (α-methylstyrene) -block-poly (vinylphenethyl alcohol) (PαMS-bPVPA) in a selective solvent, benzyl alcohol, is investigated by time-resolved static- and dynamic-light scattering. The two PαMS-b-PVPA copolymers (KT-326, KT-327) have different block lengths and exhibit different critical micelle temperatures (CMT). Time evolution of apparent molecular weight (Mapp), apparent radius of gyration and apparent hydrodynamic radius have been measured for mixtures with different mixed ratios after quenching from the unimer region to the micelle region. The time constants for micellization processes are obtained from the time evolution of Mapp. At 35°C, which is below the CMT of KT-327 but above that of KT-326, comicellization is found to proceed in two steps. The time constant τ1co of the first fast process depends on the KT-327 concentration and is smaller than the time constant τ1 of pure KT-327 micelles, because the concentration of copolymer increases by the presence of KT-326. The time constant τ2co of the second slow process increases with the KT-327 concentration. This implies that the decomposition and the unimer-entry in comicelles that have been formed at the low KT-327 concentration is faster than those in KT-327 pure micelles. At 15°C, which is below both of the CMT's of block copolymers, the time constant τ1co are between those of pure KT-326 and KT-327 and more affected by the micellization rate of the faster component KT-327. In the micellization at 15°C after annealing at 35°C, only the second process is observed in the KT-327-rich solutions, where KT-326 unimers enter into the comicelles formed at 35°C. On the other hand, in the KT-326-rich solutions, new pure KT-326 micelles are formed predominantly.
