The phase structure and molecular dynamics in poly(styrene-b-isoprene) diblock copolymer

Molecular dynamics of polyisoprene, polystyrene and poly(styrene-b-isoprene) diblock copolymer has been studied by means of broadband dielectric and magnetic resonance spectroscopies. The measurements of dielectric permittivity as well as NMR second moment, spin–lattice relaxation times T1 and T1ρ in wide range of temperature were performed. It was found that the copolymer exhibits all motions observed in the neat components i.e., three motions connected with polyisoprene blocks (segmental, normal-mode and methyl group rotation) and one (segmental) related to polystyrene blocks. The mutual interaction between polystyrene and polyisoprene chains leads to stiffening of polyisoprene blocks and loosening of polystyrene structure. The polyisoprene segmental and normal-mode motions were analyzed in terms of the Havriliak–Negami model and Vogel–Fulcher–Tamman (VFT) relation. Based on NMR spin-diffusion experiment the size of polystyrene domains in copolymer was evaluated and accounts to 9 nm.