Dynamics of copolymer micelles in an entangled homopolymer matrix

The dynamics of block copolymer micelles, with a glassy polystyrene core and polyisoprene corona, in a matrix of linear entangled polyisoprene (PI) chains, has been investigated by forced Rayleigh scattering (FRS), dynamic mechanical measurements, and dielectric relaxation spectroscopy. The concentration of micelles has been varied from 10 to 50 wt % copolymer. FRS measurements revealed two dynamical processes at low temperature. The slower of these processes has been identified as micellar diffusion, the faster as rotation of individual micelles. Dynamic mechanical measurements have shown three relaxation modes: (i) PI segmental relaxation; (ii) relaxation of matrix chains or of corona polyisoprene blocks; (iii) relaxation of individual micelles. The first two processes have been confirmed by dielectric relaxation spectroscopy, whereas the slowest one has coincided with the relaxation time related to self-diffusion of micelles detected by FRS when extrapolated to the length scale of the micelle dimensions. Results are also compared to those of recent studies of copolymer micelles in a nonentangling homopolymer matrix.