Adsorption and aggregation of carbosiloxane dendrimers on mica and pyrolytic graphite were investigated by scanning force microscopy (SFM). The aggregation process started from (i) single molecules which coagulated to (ii) clusters and (iii) fluid droplets followed by formation of (iv) a complete layer on the solid substrate. The molecules were displayed as a globular particle with a diameter of about 2.5 nm. Tapping SFM of the liquid was possible due to the fact that the dendrimer undergoes a transition to a viscoelastic state below the tapping frequency of about 360 kHz. Dynamic shear compliance experiments have shown a plateau of 5 -lo-' Pa-' around this frequency. Dendrimer droplets slowly spread into polygonal lamellae with a thickness of two molecular layers. The structures indicate a rather regular dense packing of the globular molecules.

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Self-diffusion of three high generations (the fifth, sixth, and seventh) of poly(allylcarbosilane) dendrimer in solutions with deuterated chloroform has been studied over a wide range of macromolecular concentrations (φ). Diffusivity has been measured by NMR with a pulsed gradient of the magnetic field. It is shown that concentration dependences of the dendrimer self-diffusion coefficients (D) can be reduced to the generalized concentration dependence. Over the range of volume concentrations from 0.01 up to 0.55, the curve of the generalized dependence of D for dendrimers coincides with the analogous dependence for globular protein in aqueous solutions. Analogous to the universal concentration dependence of D for linear polymers in solvent, the generalized concentration dependence of dendrimers tends to the asymptote D′(φ)/D 0 ∝ φ 0 ) 1 in the limit of extremely dilute solutions and to the asymptote D′(φ)/D0 ∝ φ -3 in the range of concentrated solutions 0.3 < φ < 0.55. Here, D0 ) limφf0 D(φ) and D(φ) are the self-diffusion coefficients of dendrimer in an extremely dilute solution and in a solution with macromolecular concentration φ, respectively. D′(φ) ) D(φ)/L(φ), where L(φ) is a normalizing function, taking into account the change of the local mobility of dendritic branches as the macromolecular concentration increases; the L(φ) functions have been experimentally extracted from the concentration dependence of the longitudinal relaxation times for the dendrimers in solutions studied.

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.