ON THE LOCATION OF THE FREE ENDS OF THE INSOLUBLE BLOCK IN MICELLES FORMED BY DIBLOCK COPOLYMERS

Nonradiative singlet energy transfer has been used to monitor the formation of micelles by diblock copolymers of poly(styrene) and poly(oxyethylene). The acceptor is placed at the junction between the two blocks in sample A1. The donor is placed either at the junction point between the blocks (D1) or free end of the block of poly(styrene) (D2). The experiment finds similar efficiencies of nonradiative singlet energy transfer in micelles formed by D1 and A1, and micelles formed by D2 and A1. This result implies that the free ends of the insoluble blocks do not seek out the center of mass of the micelle, but instead have a distribution throughout the micelle that is similar to the distribution of the junction points. Therefore the result confirms a crucial prediction from a recent simulation of the internal structure of the micelle formed by diblock copolymers in a selective solvent.