From hard to soft confinement in a symmetric block copolymer: local and segmental dynamics

Abstract

The dynamics of a diblock copolymer in the phase separated lamellar structure and in the mixed state has been studied by dielectric spectroscopy. By choosing a system in which the glass transition temperatures of the two constituent polymers are not very different, we were able to investigate the differences between hard and soft confinement imposed by the more rigid chains. The results indicate that under hard confinement, the segmental dynamics of the low T_g component experiences a slowing down due to interaction with the more rigid chains in both phase separated and mixed cases. For the phase separated case no difference in the dynamics of the low T_g block is observed upon going from the hard to the soft confinement regime. However for the mixed system under soft confinement, i.e. at temperatures higher than the T_g of the more rigid polymer block, a slowing down of the dynamics of the low T_g block polymer towards the dynamics of the more rigid block is clearly evidenced.