Relaxation time block copolymer exchange

The main part is then devoted to the equilibrium exchange kinetics of selected PEP-PEO micellar systems. We report on TR-SANS measurements in pure water that, independently of block copolymer molecular weight, composition, and temperature, revealed frozen micelles. This review further concerns the effect of tuning the kinetics by addition of co-solvents, i.e., reduction of y. The relaxation behavior of some selected systems revealing chain exchange dynamics that can be resolved by TR-SANS wfll be presented, followed by a discussion of the main observation, namely, the unexpected appearance of a pseudo-logarithmic time decay of the relaxation function. 

Stop-flow experiments have been performed by Tuzar and Kratochvil [7] and more recently by Kositza et al. [128]. In analogy to low molar weight surfactants, it could be shown that two relaxation processes have to be considered for block copolymer micellar systems the first in the time scale of tens of microseconds, associated to unimer exchange between micelle and bulk solution, and the second, in the millisecond range, attributed to the rearrangement of the micelle size distribution. Major differences were observed between A-B diblock and A-B-A triblock copolymers, which could be explained by the fact that the escape of a unimer, which has to disentangle from the micellar core, might be much easier in a diblock than in a triblock structure. 

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