A low-resolution ab initio shape determination was performed from small-angle neutron and X-ray scattering (SANS and SAXS) curves from solutions of polycarbosilane dendrimers with the three-functional and the four-functional branching centre of the fourth, fifth, sixth, seventh and eighth generations. In all cases, anisometric dendrimer shapes were obtained. The overall shapes of the dendrimers with the three-and four-functional branching centres were oblate ellipsoids of revolution and triaxial ellipsoids, respectively. The restored bead models revealed a pronounced heterogeneity within the dendrimer structure. The density deficit was observed in the central part and close to the periphery of the dendrimers. The fraction of the overall volume of the dendrimers available for solvent penetration was about 0.2-0.3. These results may help in the design of new practical applications of dendrimer macromolecules.
The structural characteristics of polycarbosilane dendrimers with different molecular architecture were determined in solutions by small angle neutron and X-ray scattering. The same linear dimensions were sized up for the dendrimers both in benzene and chloroform. A solvent molecules penetration inside dendrimer structure in amount up to 30 vol.-% was found from the comparison of the partial and effective scattering volume for the dendrimers in solution.
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