This paper compares the results yielded by two methods of small-angle X-ray scattering data analysis for semicrystalline polymer blends. The first method is based on the use of a theoretical modeling for isotropic samples and a subsequent curve fitting. The second one is a more familiar method, based on the calculation of the linear one-dimensional correlation function. The experimental material considered for this purpose deals with a series of semi-crystalline blends of poly(vinylidene fluoride) and poly(methyl methacrylate), with a PVDF content covering the range 50 wt%–100 wt%. The results obtained by both calculation methods are systematically confronted to the crystallinity degrees deduced from wide angle X-ray scattering patterns. 1. Introduction A structural periodicity was recognized in semi-crystalline polymers and polymer blends which typically consist of crystalline and amorphous domains with dimensions in the nanometer range, which form lamellar stacks embedded in a spherulitic superstructure [1]. The final properties of such a polymer or a polymer blend depend on the volume fraction of the crystalline domains and subsequently on the linear degree of crystallinity as well as on their size and structure. An additional important factor is the linkage which exists between the crystalline lamellae and the amorphous interlamellar regions. In most cases, small-angle X-ray scattering (SAXS) patterns of isotropic semi-crystalline polymers and polymer blends are analyzed using the related linear one-dimensional correlation function (CF) obtained by Fourier transformation of the Lorentz-corrected experimental (SAXS) intensity distribution versus the scattering vector. Knowing and using the methods derived by Vonk and Kortleve [2, 3], and Strobl et al. (1980) [4, 5], one can determine the fundamental parameters of the lamellar stacks, namely, the thickness and of the crystalline lamellae and amorphous layers, respectively. The average long period can simply deduced by . These quantities can also be determined by modeling the lamellar stacks structure and obtaining the best fit of a theoretical SAXS intensity distribution, calculated for the assumed model of stacks, to the experimental SAXS curve. The number of optimized parameters of the stacks depends on the complexity of the model. Generally, in the curve-fitting method, lamellar stacks are characterized by the average thickness of the crystalline lamellae and the amorphous layers and by the independent distribution functions of the crystalline lamellae and the amorphous layer thicknesses and ,
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