Analysis of stability and viscoelastic properties of melts of polystyrene-block-polyisoprene diblock copolymers in oscillatory shear and creep-recovery experiments
AbstractIn this study, the rheological properties of polystyrene-block-polyisoprene (PS-b-PI) diblock copolymer melts with different types of morphology are analysed. Using the technique of anionic polymerization three different PS-b-PI diblock copolymers with a spherical, cylindrical and lamellar morphology, respectively, were synthesised. The objective of our study was to determine the viscous and elastic properties of these PS-b-PI diblock copolymers and to investigate the influence of morphology on the viscoelastic properties at short and long times. The analysis of our experiments reveals that morphological changes take place in the melt which lead to changes of the dynamic moduli. Furthermore, all three diblock copolymers of this study reveal a non-terminal behaviour in oscillatory shear flow in the microphase-separated state. Our creep recovery experiments indicate that microphase-separated diblock copolymers are characterised by a pronounced recoverable deformation.