Microstructure analysis using temperature-induced contrast variation in small-angle scattering

We propose to introduce Temperature-Induced Contrast Variation (TICV) as a technique for improving the specificity of microstructure analyses obtained using small-angle scattering methods. TICV exploits the fact that, at temperatures well removed from melting or annealing regimes, the scattering contrast in many multicomponent systems exhibits a significant temperature dependence while the form factors for the scattering processes change only slightly. Difference scattering patterns formed by subtracting the pattern measured at a suitable reference temperature from the pattern obtained at another temperature emphasize those components of the microstructure that vary most strongly with temperature over the chosen range. This can facilitate an effective separation of the observed scattering patterns into separate components for differing scattering mechanisms. Examples of distinct scattering mechanisms commonly found in polymers include liquid-like scattering from amorphous components, contributions from the intramolecular amorphous halo, Guinier scattering from inclusions, and the scattering from ordered stacks of crystalline lamellae. The experimental data presented here provide qualitative demonstrations of general features of the method. Further work is needed to obtain improved descriptors to characterize microstructure in these systems.