A BLOB MODEL TO STUDY POLYMER-CHAIN DYNAMICS IN SOLUTION

Excimer formation was used as a tool to probe the dynamics in tetrahyd rofuran solution of two ethylene propylene copolymers labeled with pyr ene. The excimer kinetics were analyzed by a new model. This model con siders that the polymer chain can be divided into equivalent blobs. Th e fluorescent probe is assumed to be distributed randomly among the bl obs. As a consequence, the occupancy probability of chromophores insid e a blob follows a Poisson distribution. We can describe the kinetics of the system in terms of the theory of excimer formation in micellar systems. In this way we can obtain the blob size and the magnitude of the first-order rate constant for excimer formation in the blob. The m odel is applicable to polydisperse polymer systems and provides inform ation by shifting the focus of attention from chain-length-dependent t o blob-size-dependent behavior.