Strain-induced large fluctuations during stress relaxation in polymer melts observed by small-angle neutron scattering. ?Lozenges?, ?butterflies?, and related theory

Structural development of dynamically asymmetric polymer blends under uniaxial stretching

“…As shown in Fig. 2(a), the two-dimensional scattering pattern becomes a little anisotropic a short time after stretching but the intensity becomes larger along both the parallel and perpendicular directions, which is similar to the 'lozenge pattern' observed by Boue et al (1991) Stress versus strain curves for various blends.…”

“…On the other hand, for mixtures of short deuterated polystyrene (PS) chains dispersed in very long normal PS chains or in rubbers, structural studies during relaxation after stretching have been extensively investigated using small-angle neutron scattering (SANS) by Bastide et al (Bastide et al, 1988, 1990Boue et al, 1991;Zielinski et al, 1992;Ramzi et al, 1995). In their studies, an elliptical pattern was observed for short durations of relaxation after stretching, while a butterfly pattern was observed for long durations.…”

``Lozenge'' Contour Plots in Scattering from Polymer Networks

“…A common observation in these experiments is that contour plots of the two dimensional scattering intensity take on a diamond or "lozenge" shape. The experiments fall mainly into two categories; for pure networks with dilute labeled chains [1] the lozenge pattern is permanent and does not relax, but if the labeled species is mobile the lozenge pattern relaxes and is a precursor to "butterfly" contour patterns [2,3]. In this Letter we demonstrate that the lozenge shape can largely be explained by taking into account those chain sections in the system which are not directly deformed by the stretch.…”

“…We now briefly discuss the lozenges observed in the recent butterfly scattering experiments [2,3]. The butterfly is the name given to a contour plot where the contours have a characteristic "figure 8" shape, aligned in the stretch direction.…”

Microphase Separation in a Model Graft Copolymer

“…Looking at the higher-q regions of the contour plots and at the P N S data which does not include much of the data in the low-q region below the peak, we can see the scattering pattern change over to one that is more like the conventional ellipticai pattern. 13 In fact, applying a function like Equation 2 to these (higher-q) data result in anisotropy in L, but not in 5. In butterfly patterns arising from gels, the "correlation length" is typically quite anisotropic.12 All of this probably means that the butterfly phenomenon is more connected to the response of the regions over which the lamellae have a correlated orientation.…”