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 temp eratures well removed from melting or annealing regimes, the scattering con trast in many multicomponent systems exhibits a significant temperature dep endence while the form factors for the scattering processes change only sli ghtly. Difference scattering patterns formed by subtracting the pattern mea sured at a suitable reference temperature from the pattern obtained at anot her temperature emphasize those components of the microstructure that vary most strongly with temperature over the chosen range. This can facilitate a n effective separation of the observed scattering patterns into separate co mponents for differing scattering mechanisms. Examples of distinct scatteri ng mechanisms commonly found in polymers include liquidlike scattering from amorphous components, contributions from the intramolecular amorphous halo , Guinier scattering from inclusions, and the scattering from ordered stack s of crystalline lamellae. The experimental data presented here provide qualitative demonstrations of general features of the method. Further work is needed to obtain improved d escriptors to characterize microstructure in these systems.