what is measured?
The measured quantities here are the average long period and the average crystalline layer thickness of the lamellae present in most semi-crystalline polymers.
The lamellae consist in a regular alternation of amorphous and crystalline phases stacked on parallel sheets. This is usually the description at the mesoscale, of the basic spherulite crystalline morphology present in semi-crystalline polymers.
Figure 1. Example of the auto-correlation of the electron density in a lamellar structure, as function of size. The analysis of the correlation function provides information on the long and short periods of the lamellar structure.
For phase analysis of other types of polymers or surfactants, please refer to our Phase identification webpage.
Typical samples for this measurement are:
Samples can be studied in various in situ conditions.
Methods & standards
Standards & methods used for lamellar spacing determination:
- Ref: G.R. Strobl, M.J. Schneider and IG.G. Voigt-Martin, Journal of Polymer Science, 1980, 18, 1361-1381. doi: 10.1002/pol.1980.180180615
XSACT analysis software implements the above method. Example of customer publications making use of XSACT for lamellar spacing determination:
- Tencé-Girault, S et al. “Simultaneous SAXS-WAXS Experiments on Semi-Crystalline Polymers: Example of PA11 and Its Brill Transition“. Crystals, vol 9, 5, pp. 271 (2019)
- Tencé-Girault, S et al. “Quantitative Structural Study of Cold-Crystallized PEKK“. ACS Appl. Polym. Mater. (2021)
Why use SAXS for lamellar spacing determination:
Advantages of SAXS for lamellar spacing determination?
- With SAXS you get direct access to local organization of polymeric material.
- It provides quantitative interpretation of the amorphous phase and crystalline phase
- The correlation function analysis gives access to the detailed description of the lamellar stack, composed of an amorphous phase and a crystalline phase.
- SAXS in a non-destructive method.
- SAXS does not require sample preparation such as staining.