Microphase Reorientation in a Block Copolymer Melt as Detected by FT-Rheology and 2D-SAXS

The alignment kinetics for the orientation/reorientation behavior of the microphase of a lamellar PS-b-PI diblock copolymer under large amplitude oscillatory shear (LAOS) at a shear frequency ω1/2π is studied. This blockpolymer serves as a model compound for complex morphologies and textures. The degree of mechanical nonlinearity was online monitored via the intensity of the mechanical higher harmonic response at 3ω1 during the orientation nd reorientation process (FT-Rheology). FT-Rheology was combined with an quantification of the orientation using 2-dimensional small angle X-ray scattering (2D-SAXS). Within this study the kinetics of the change in macrophase alignment from the parallel to the perpendicular orientation is induced by applying two different oscillatory shear conditions. Improved parallel alignment after increasing the shear frequency as well as spatial heterogeneous alignment kinetics are detected. Thus, FT-Rheology offers a new and simple way for online monitoring for orientation kinetics in complex materials e.g. in foods

Microstructure and rheological properties of triblock copolymers under extrusion conditions

Triblock copolymers with different microstructures were subjected to macroscopic deformations under extrusion using a miniaturized high pressure capillary rheometer. The rheological properties of the triblock copolymers investigated depend strongly on composition and configuration of the building units, which are microphase separated into complex morphologies, Under extrusion conditions they organize to stretched layer systems, which are perpendicular oriented in respect to the direction of the shear plane and the orientation decreases again at high shear rates. The macroscopic order leads to integral values of the order parameter from two- dimensional small X-ray scattering and form birefringence, which show a good correlation in the relevant shear rate range. Furthermore, a master curve of the form birefringence can be obtained

Microphase reorientation in block copolymer melts as detected via FT rheology and 2D SAXS

The alignment kinetics of the orientation/reorientation behavior of the microphase of a lamellarPS-b-PI diblock copolymer under large-amplitude oscillatory shear conditions is studied. By online monitoring the degree of the mechanical nonlinearity during the orientation process-as determined via the higher harmonics in Fourier transform (FT) rheology-and investigation of the orientational distribution by 2- dimensional small-angle X-ray scattering, we followed the kinetics of the microphase alignment for two different experimental shear conditions, Improved parallel alignment after increasing the shear frequency as well as spatially heterogeneous alignment via bimodal: parallel and perpendicular alignment of the lamellae is detected by both methods. Thus, FT rheology offers a new and simple way for online monitoring complex reorientation kinetics

Microphase reorientation in block copolymer melts as detected via FT rheology and 2D SAXS

The alignment kinetics of the orientation/reorientation behavior of the microphase of a lamellarPS-b-PI diblock copolymer under large-amplitude oscillatory shear conditions is studied. By online monitoring the degree of the mechanical nonlinearity during the orientation process-as determined via the higher harmonics in Fourier transform (FT) rheology-and investigation of the orientational distribution by 2- dimensional small-angle X-ray scattering, we followed the kinetics of the microphase alignment for two different experimental shear conditions, Improved parallel alignment after increasing the shear frequency as well as spatially heterogeneous alignment via bimodal: parallel and perpendicular alignment of the lamellae is detected by both methods. Thus, FT rheology offers a new and simple way for online monitoring complex reorientation kinetics