Since the pioneering works on dendrimer synthesis the question about the existence of a free space (hollow core or cavity) within dendrimers and the possibility of its use for practical purposes plays an important role. Theoretical and experimental studies of this problem have a long history; at the same time there is still no systematic exposition of the results of researches on this topic in the literature. The first part of this report is devoted to a detailed discussion of the dendrimers’ structure and a critical analysis of the current state of the theory and existing experimental data for homopolymeric dendrimers in dilute solution.
In the rest part of the report the studies of copolymeric dendrimers, in which the end segments have different physico-chemical properties than the inner ones, are considered. It is found that the incompatibility between the terminal and the inner segments is the main factor favoring formation of a "hollow" interior in the dendrimer in dilute solution [1]. It is shown that the solvent quality with respect to terminal groups plays an important additional role.
Obtained results allow us to explain molecular dynamics simulation results [2] and NMR experimental data [3] for G=4 generation carbosilane dendrimer with terminal cyanobiphenyl groups in dilute chloroform solution. In this copolymer dendrimer the "hollow" interior is formed with decreasing temperature which corresponds to increasing segregation effect.

[1] D.A. Markelov , A.A. Polotsky, T.M. Birshtein // J. Phys. Chem. B. 2014, 118, 14961.
[2] D.A. Markelov, M.A. Mazo, N.K. Balabaev, Yu.Ya. Gotlib // Polym. Sci., Ser. A 2013, 55, 53
[3] D.A. Markelov, V. V. Matveev, P. Ingman, M.N. Nikolaeva, E. Lähderanta, V.A. Shevelev, N.I. Boiko // J. Phys. Chem. B. 2010, 114, 4159