Organic nanotubes created from mesogenic derivatives

Light-Responsive Supramolecular Nanotubes-Based Chiral Plasmonic Assemblies

We describe the fabrication of dual-responsive (thermo/light) chiral plasmonic films. The idea is based on using photoswitchable achiral liquid crystal (LCs) forming chiral nanotubes for templating helical assemblies of Au NPs. Circular dichroism spectroscopy (CD) confirms chiroptical properties coming from the arrangement of organic and inorganic components, with up to 0.2 dissymmetry factor (g-factor). Upon exposure to UV light, organic molecules isomerize, resulting in controlled melting of organic nanotubes and/or inorganic nanohelices. The process can be reversed using visible light and further modified by varying the temperature, offering a control of chiroptical response of the composite material. These properties can play a key role in the future development of chiral plasmonics, metamaterials, and optoelectronic devices.

The nanostructure of rod-like ascorbyl dipalmitate nanoparticles stabilized by a small amount of DSPE-PEG

Previously, we reported the formation of 100-200 nm disk- and tube-like nanoparticles by hydration of _L-ascorbyl 2,6-dipalmitate (ASC-DP) and distearoylphosphatidylethanolamine polyethylene glycol 2000 (DSPE-PEG) films prepared at an initial molar ratio of 2:1. This study investigated the feasibility of nanoparticle formation with higher ASC-DP loading. Although particle size distribution determined by dynamic light scattering showed a multimodal pattern including micro-sized particles at a molar ratio of 3:1, the mean particle size gradually decreased with a further increased molar ratio. Homogeneous ca. 240 nm nanoparticles with a unimodal size distribution were obtained at a molar ratio of 10:1. FE-TEM showed that the nanoparticles at a molar ratio of 10:1 were rod-shaped with a diameter of ca. 100 nm and a length of ca. 300 nm. After centrifugation, X-ray analysis of the nanoparticle precipitates showed that these rod-like nanoparticles were composed of a series of lamellar structures with 3.7 nm repeated units. The molar ratio of ASC-DP/DSPE-PEG in the nanoparticle precipitates determined by ¹H NMR measurements was 68.8:1. The rod-like nanoparticles should be composed of a core-shell structure, where a small amount of DSPE-PEG covers the lamellar structure of ASC-DP. Further increase in the ASC-DP/DSPE-PEG molar ratio over 33:1 no longer provided nanoparticles. Hence, to prepare a stable ASC-DP nanoparticle suspension, it is necessary to prepare ASC-DP/DSPE-PEG films containing at least 3 mol% DSPE-PEG.

Microfluidics for the rapid and controlled preparation of organic nanotubes of bent-core based dendrimers

Recently, bent-core molecules have emerged as excellent building blocks for the obtaining of nanostructures in solvents. Herein, we report the use of a coaxial microfluidic system as a promising tool to control the self-assembly of non-conventional bent-core amphiphiles. Moreover, a TEM study to comprehend the hierarchical self-assembly process in solution was carried out. The proposed tool provides both a cost-effective platform to save hard-to-synthesise reagents and a rapid method to screen a plethora of different parameters, i.e., THF/water ratio, residence time, concentration of the amphiphile, temperature and pH. The experiments allowed to test for the first time the suitability of microfluidics for the self-assembly of bent-core molecules, as well as the study of a range of conditions to control the assembly of different nanostructures in a rapid and controlled manner. Additionally, organic nanostructures were combined with gold nanoparticles to prepare nanocomposites with enhanced properties. Both organic and hybrid nanostructures were also obtained in the solid state. These results may inspire scientists working on supramolecular chemistry and bent-core molecules expanding the scope of microfluidic systems for the self-assembly of other low-molecular-weight compounds.

How mobile phase composition and column temperature affect enantiomer elution order of liquid crystals on amylose tris(3-chloro-5-methylphenylcarbamate) as chiral selector

A comprehensive study into the effects of mobile phase composition and column temperature on enantiomer elution order was conducted with a set of chiral rod-like liquid crystalline materials. The analytes were structurally similar and comprised variances such as length of terminal alkyl chain, presence of chlorine, number of phenyl rings, and type of chiral center. Experiments were carried out in polar organic and reversed-phase modes using amylose tris(3-chloro-5-methylphenylcarbamate) immobilized on silica gel as the chiral stationary phase. For all liquid crystals, reversal of elution order of enantiomers was observed based on type of used cosolvent and/or its content in the mobile phase; for some of the liquid crystals a temperature-induced reversal was also observed. Both linear and nonlinear dependencies of natural logarithm of enantioselectivity on temperature were found. Tested mobile phases comprised pure organic solvents and binary and tertiary mixtures of acetonitrile with organic solvents and/or water. Effect of acidic/basic mobile phase additives was also tested. Effect of structure of chiral selector is briefly discussed.

Helical Nanofibers Formed by Palladium-Mediated Assembly of Organic Homochiral Macrocycles Containing Binaphthyl and Pyridyl Units

Herein, we report the synthesis and characterization of homochiral macrocycles, in which molecular rigidity, combined with the presence of multiple functional groups, allow for the assembly of helical nanostructures. 1,1'-bi-2-naphthol (Binol) units are used as robust chirality inducers, and pyridyl units embedded within the molecular frameworks allow the assembly, upon coordination with Pd(II) metal ions, of the macrocyclic building blocks. CD and NMR spectroscopies show the formation of ordered 1D assembly in solution. AFM studies indicate that the molecular systems are capable of forming nanoscale structures. The effective transfer of chiral information results in helical nanofibers, with lengths ranging from a few hundreds of nanometers to some micrometers. AFM line profiles reveal a helical longitudinal period of about 50 nm and a transverse width of 25 to 45 nm after deconvolution.

Self-Assembling Behavior of Smart Nanocomposite System: Ferroelectric Liquid Crystal Confined by Stretched Porous Polyethylene Film

The control and prediction of soft systems exhibiting self-organization behavior can be realized by different means but still remains a highlighted task. Novel advanced nanocomposite system has been designed by filling of a stretched porous polyethylene (PE) film with pore dimensions of hundreds of nanometers by chiral ferroelectric liquid crystalline (LC) compound possessing polar self-assembling behavior. Lactic acid derivative exhibiting the paraelectric orthogonal smectic A* and the ferroelectric tilted smectic C* phases over a broad temperature range is used as a self-assembling compound. The morphology of nanocomposite film has been checked by Atomic Force Microscopy (AFM). The designed nanocomposite has been studied by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), small and wide-angle X-ray scattering and broadband dielectric spectroscopy. The effect of a porous PE confinement on self-assembling, structural, and dielectric behavior of the chiral LC compound has been established and discussed. While the mesomorphic and structural properties of the nanocomposite are found not to be much influenced in comparison to that of a pure LC compound, the polar properties have been toughly suppressed by the specific confinement. Nevertheless, the electro-optic switching was clearly observed under applied electric field of low frequency (210 V, 19 Hz). The dielectric spectroscopy and X-ray results reveal that the helical structure of the ferroelectric liquid crystal inside the PE matrix is completely unwound, and the molecules are aligned along stretching direction. Obtained results demonstrate possibilities of using stretched porous polyolefins as promising matrices for the design of new nanocomposites.