Abstract:

The positron lifetime technique has been used to study the temperature behavior of micelle in solution of polystyrene-polydimethylsiloxane diblock copolymer in n-heptane. The results indicate that positron annihilation parameters are found to be sensitive to structural and microphase changes taking place in the micellar solutions. The abrupt changes in the o-Ps lifetime and intensity observed at certain temperature appear to be associated with variations in the aggregation state of the copolymer molecules in solutions. Above the critical micelle temperature the o-Ps lifetime increases sharply with increasing temperature. This behavior indicates the process of disintegration of molecular aggregates to free copolymer molecules.

Key words: Positron annihilation;Blok copolymer;Micellar solution;Temperature effect