THE EFFECTS OF STEADY SHEAR ON THE ORDER AND ORIENTATION OF A DIBLOCK COPOLYMER MELT USING IN-SITU SMALL-ANGLE NEUTRON SCATTERING

摘要

To understand the effects of processing on polymer melts requires experimental techniques that show the orientation of materials during processing. Small-angle neutron scattering (SANS) has been recently adapted to allow for examination of polymeric materials during shear. This work will highlight the benefits of combining shear and scattering techniques to study morphology, ordering and orientation of a polystyrene-polybutadiene diblock copolymer melt under steady shear flow. The order-disorder transition temperature (Tom) is unchanged at low shear rates but increases by ΔT_(ODT) ≈ γ~(1.35) at high shear rates. An analysis of the degree of orientation using order parameter calculations shows that maximum ordering occurs within 30 minutes of shear and better alignment is obtained at low shear rates. A large relative increase in the order parameter (up to 600 %) is seen upon cessation of the shear flow.