Silica microspheres encapsulating ibuprofen in separated domains at the nanometre scale are formed by spray-drying and sol-gel processes. A detailed (1)H and (13)C NMR study of these microspheres shows that ibuprofen molecules are mobile and are interacting through hydrogen bonds with other ibuprofen molecules. (1)H magnetisation exchange NMR experiments were employed to characterize the size of the ibuprofen domains at the nanometre scale. These domains are solely formed by ibuprofen, and their diameters are estimated to be ∼40 nm in agreement with TEM observations. The nature and formation of these particular texture and drug dispersion are discussed.
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.
International audienceA new one-pot synthesis route associating sol–gel, self-assembly and spray drying allows the formation of microspheres with tuneable textures (worm-like mesophases, separated spheroid nanodomains, core–shell organisation) and drug delivery properties (from burst to delayed release)
Abstract:In this article small-angle X-ray scattering (SAXS) is used to characterize the structural parameters of semi-crystalline blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate). Different blend compositions from 100 to 50 wt.-% of PVDF were investigated. The samples were considered to be isotropic. As two-dimensional SAXS patterns with cylindrical symmetry were examined, a single direction in the SAXS pattern plane was chosen to collect and plot absolute intensities versus the scattering vector. Using the one-dimensional (linear) electron density correlation and interface distribution functions obtained, respectively, from the Fourier-transformed Lorentz-corrected experimental scattering intensity and from the interference function, structural parameters such as the minimal value and the most probable value of the long period, the average lamellar thickness, and the volume crystallinity were determined.
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