Crystalline-amorphous features lamella

In the case of a semicrystalline polymer such as PP, the microstructural features are likely to appear at the scale of the spherulites (typically 5-100 pm in diameter) or even closer at the scale of the long period of the lamellar stacks (10-100 nm). In order to accede to the latter details, it was shown previously (48) that etching of the polished surface with oxidizing acids engraves the amorphous interstices and let the crystalline morphology appear lamellae, or at least stacks of lamellae, become visible. 

The semi-crystalline nature of starch is well known and its most important feature is the alternation of long-range molecular order and amorphous regions, defining the corresponding alternation of crystalline and amorphous lamellae [14, 16, 20, 31],... 

Small-angle x-ray scattering (SAXS) probes structural features at the mesoscopic length-scale (Section 1.9.2). It can be used to measure the radius of gyration of polymers in solution, via Eq. (1.27), which can be up to hundreds of nanometres. Semicrystalline polymers form lamellae, which are layered systems with a layer period of the order of 10 nm. Such lamellar stacks diffract x-rays at small angles, indeed they are a one-dimensional lattice, and Bragg s law can be used to determine the layer period. Furthermore, the relative intensities of the peaks depend on the distribution of amorphous and crystalline material, and this can be analysed to provide a model of the electron density profile normal to the layers. 

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