Solvent-Free Model for Self-Assembling Amphiphilic Cyclodextrins. An Off-Lattice Monte Carlo Approach in Two Dimensions

Principles and applications of cyclodextrin liquid crystals

Cyclodextrin-based liquid crystals and their emerging applications are described in this tutorial review, which covers reports from the last decade with a focus on recent developments. Although cyclodextrins are among the best studied macrocyclic host molecules and liquid crystals have found widespread technological application, the integration of cyclodextrins in liquid crystals as versatile supramolecular materials has been barely explored. However, in the last few years promising innovations in molecular design as well as proof-of-concept applications such as ion-conductive and proton-conductive liquid crystals, nanoparticle additives for liquid crystal display technology, polyrotaxane-based liquid crystals and liquid crystal-based sensors have been reported. We discuss various examples of cyclodextrin-based liquid crystals that demonstrate the significant potential of these unique soft materials for future research and interdisciplinary applications.

Self-Assembly of Amphiphilic Biotransesterified β-Cyclodextrins: Supramolecular Structure of Nanoparticles and Surface Properties

A series of β-cyclodextrin (βCD) amphiphilic derivatives with varying degrees of substitution were prepared by acylating βCDs on their secondary face using thermolysin to catalyze the transesterification. After dissolution in acetone, the βCD-C_n derivatives (n = 8, 10, 12, 14) were nanoprecipitated in water, where they self-organized into structured particles that were characterized using cryo-transmission electron microscopy (cryo-TEM) images and small-angle X-ray scattering (SAXS) data. Two types of morphologies and ultrastructures were observed depending on the total degree of substitution (TDS) of the parent derivative. The molecules with TDS < 5 formed nanospheres with a multilamellar organization, whereas those with TDS > 5 self-assembled into barrel-like (n = 8, 10, 12) or more tortuous (n = 14) particles with a columnar inverse hexagonal structure. In particular, faceted βCD-C₁₄ particles (TDS = 7) appeared to be composed of several domains with different orientations that were separated by sharp interfaces. Ultrastructural models were proposed on the basis of cryo-TEM images and the analysis of the contrast distribution in different projections of the lattice. Complementary compression isotherm experiments carried out at the air-water interface also suggested that differences in the molecular conformation of the series of derivatives existed depending on whether TDS was lower or higher than 5.

Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a "bottom up" approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties.