Nematic-like organization of magnetic mesogen-hybridized nanoparticles.

A fluid nematic-like phase is induced in monodisperse iron oxide nanoparticles with a diameter of 3.3 nm. This supramolecular arrangement is governed by the covalent functionalization of the nanoparticle surface with cyanobiphenyl-based ligands as mesogenic promoters. The design and synthesis of these hybrid materials and the study of their mesogenic properties are reported. In addition, the modifications of the magnetic properties of the hybridized nanoparticles are investigated as a function of the different grafted ligands. Owing to the rather large interparticular distances (about 7 nm), the dipolar interaction between nanoparticles is shown to play only a minor role. Conversely, the surface magnetic anisotropy of the particles is significantly affected by the surface derivatization.

Liquid crystalline dendrimers.

In recent years, there has been an increasing interest in the field of liquid crystalline dendrimers. Such a fast development is, among other things, driven by the multiple possibilities offered by combining the mesomorphic properties of single mesogenic subunits with the supermolecular and versatile architectures of dendrimers to yield a new class of highly functional materials. The induction and the control of the mesomorphic properties (phase type and stability) in dendrimers can be achieved by a dedicated molecular design which depends on the chemical nature and structure of both the functional groups and the dendritic matrix. In particular, the intrinsic connectivity of the dendrimer such as the multivalency of the focal core and the multiplicity of the branches, both controlling the geometrical rate of growth, or the dendritic generation, plays a crucial role and influences at various stages the subtle relationships between the supermolecular structure and the mesophase structure and stability. In this critical review article, an account of the various types of dendritic systems that form liquid-crystalline mesophases along with a description of the self-organization of representative case-study supermolecules into liquid crystalline mesophases will be discussed. Some basics of thermotropic liquid crystals and dendrimers will be given in the introduction. Then, in the following sections, selected examples including side-chain, main-chain, fullerodendrimers, shape-persistent dendrimers, supramolecular dendromesogens and metallodendrimers, as representative families of LC dendrimers, will be described. In the conclusion some further developments will be highlighted. This review will not cover liquid crystalline hyperbranched and dendronized polymers that might be considered as being somehow less structurally "perfect".