Self-assembling of nanosponges to regular clusters

In order to estimate the molecular dimensions of nanosponges, we appHed dynamic light scattering and size-exclusion chromatography (SEC) to the solutions of the new species and low-angle X-ray scattering, electron microscopy, and scanning atomic force microscopy to the dry material [236, 238-240]. 

Simple calculations show that a fuUy collapsed crossUnked polystyrene molecule with a molecular weight of 370 kDa would occupy the volume of a sphere with a diameter of 10.4 nm if it could maintain the density of 

Indeed, when examined by low-angle X-ray scattering technique, the nanosponge powder scattered X-rays as a material with fluctuations in its density having a lattice spacing period of about 12 nm. SEC in tetrahydrofuran or chloroform, on both analytical and preparative scale [236], was carried out on a silica gel Diasorb Si 400 column having an acceptable performance (over 9000 theoretical plates for naphthalene in acetonitrile) 

Dynamic tight scattering [236] of fractions 3 and 2 allowed estimation of the diameter of the nanosponges as 17 nm and that of the clusters as 34 nm. Indeed, transition electron micrographs reveal the spherical shape and a distinct size difference of the two types of dry species, approximately 15-20 nm and up to 40-50 nm, respectively [236, 238]. 

By using the technique of an artificial boundary in the ultracentrifiige cell, diffusion coefficients Do for the clusters (firaction 2) and the nanosponges (fiaction 3) were determined at a single concentration of 2 g/L (Table 8.4). It has been shown earlier that the hydrodynamic parameters of these species do not depend on the concentration. This is not the case with the initial linear polystyrene, where several measurements in the concentration range of 2.5-1.0 g/L were needed, in order to extrapolate to the limiting value of the diffusion constant Dq at zero concentration. 

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