Self-Assembly, Thermotropic, and Lyotropic Phase Behavior of Guerbet Branched-Chain Maltosides

Self-Assembly of Unusually Stable Thermotropic Network Phases by Cellobiose-Based Guerbet Glycolipids

Bicontinuous thermotropic liquid crystal (LC) materials, e.g., double gyroid (DG) phases, have garnered significant attention due to the potential utility of their 3D network structures in wide-ranging applications. However, the utility of these materials is significantly constrained by the lack of robust molecular design rules for shape-filling amphiphiles that spontaneously adopt the saddle curvatures required to access these useful supramolecular assemblies. Toward this aim, we synthesized anomerically pure Guerbet-type glycolipids bearing cellobiose head groups and branched alkyl tails and studied their thermotropic LC self-assembly. Using a combination of differential scanning calorimetry, polarized optical microscopy, and small-angle X-ray scattering, our studies demonstrate that Guerbet cellobiosides exhibit a strong propensity to self-assemble into DG morphologies over wide thermotropic phase windows. The stabilities of these assemblies sensitively depend on the branched alkyl tail structure and the anomeric configuration of the glycolipid in a previously unrecognized manner. Complementary molecular simulations furnish detailed insights into the observed self-assembly characteristics, thus unveiling molecular motifs that foster network phase self-assembly that will enable future designs and applications of network LC materials.

Additives-directed lyotropic liquid crystals architecture: Simulations and experiments

In this study, alkanes and sucrose esters are employed to investigate the influence of additives on lyotropic liquid crystal architecture. After molecular dynamic simulations and experiment characterization, we showed how the additives control the structure of LLCs. By controlling the polarity of additives, the phase behavior of LLCs can be engineered to form the required structure. Dissipative particle dynamics (DPD) is introduced for simulating the self-assembly of phytantriol (PT), providing intuitionistic images and structure information, which shows that additives with low-polarity complicate the internal structure of liquid crystal systems. Then the ternary phase diagrams of additives, PT, and water are constructed to systematically study the effects of additives on the phase behavior of LLCs. Consistent with DPD simulation results, there is a certain regularity in the effects of additives on the structure of liquid crystals. The difference in the structure of LLCs is due to the variability in the critical packing parameter (CPP) obtained by changing the polarity of additives. Our findings demonstrate that additives polarity is a key factor in LLCs structure, and may pave a promising avenue for novel LLCs development and translation, determining the self-assembly process and the resulting phase of LLCs.

Surface Activity of Alkoxy Ethoxyethyl β-d-Glucopyranosides

Dioxyethene fragment (-(OCH₂CH₂)₂-) was introduced into traditional alkyl β-d-glucopyranosides to ameliorate the water solubility, and eight nonionic surfactants, that is, alkoxy ethoxyethyl β-d-glucopyranosides with alkyl chain lengths (n = 6-16), were synthesized and characterized. Their hydrophilic and lipophilic balance number, water solubility, critical micelle concentration (cmc), γ_cmc, Γ_max, and hygroscopic rate decreased with an increase in the alkyl chain length. Hexadecoxy ethoxyethyl β-d-glucopyranoside had no water solubility at 25 °C. Decoxy ethoxyethyl β-d-glucopyranoside had the best emulsifying property in the toluene/water and n-octane/water systems and the strongest foaming property, whereas dodecoxy ethoxyethyl β-d-glucopyranoside had the best emulsifying property in the rapeseed oil/water system. Such β-d-glucopyranosides (n = 6-12) exhibited excellent surface activity. In addition, for the binary mixture of alkoxy ethoxyethyl β-d-glucopyranosides (n = 8, 10, 12) and sodium dodecyl sulfate or cetyl trimethyl ammonium chloride, their cmc values were lower than the pure β-d-glucopyranosides, indicating that they had synergistic interactions. The fan focal conic textures of alkoxy ethoxyethyl β-d-glucopyranosides (n = 7-16) were observed during the cooling process under a polarizing optical microscope. Alkoxy ethoxyethyl β-d-glucopyranosides (n = 14, 16) had the related melting points and the clear points with differential scanning calorimetry. With β-d-glucopyranosides (n = 6-16) and n-butanol as the surfactant and cosurfactant, respectively, and with cyclohexane as the oil phase, the related microemulsion areas in their pseudoternary phase diagram system were investigated with the visual observation at 25 °C. Along with the slashing requirements of petroleum consumption, environmental protection, and green and sustainable development, nonionic sugar-based alkoxy ethoxyethyl β-d-glucopyranosides should be expected to have their potential practical application because of their strengthened hydrophilicity, improved water solubility, and enhanced surface activity.

Synthesis, Simulation, and Self-Assembly of a Model Amphiphile To Push the Limits of Block Polymer Nanopatterning

Efforts to create block-polymer-based templates with ultrasmall domain sizes has stimulated integrated experimental and theoretical work in an effort to design and prepare self-assembled systems that can achieve unprecedented domain sizes. We recently reported the utilization of molecular dynamics simulations with transferable force fields to identify amphiphilic oligomers capable of self-assembling into ordered layered and cylindrical morphologies with sub-3 nm domain sizes. Motivated by these predictions, we prepared a sugar-based amphiphile with a hydrocarbon tail that shows thermotropic self-assembly to give a lamellar mesophase with a 3.5 nm pitch and sub-2 nm nanodomains above the melting temperature and below the liquid-crystalline clearing temperature. Complementary atomistic simulations of the molecular assemblies gave morphologies and spacings that were in near-perfect agreement with the experimental results. The effective combination of molecular design, simulation, synthesis, and structural characterization demonstrates the power of this integrated approach for next-generation templating technologies.

Branched alkyldimethylamine oxide surfactants: An effective strategy for the design of high concentration/low viscosity surfactant formulations

HYPOTHESIS

The rational design of branched-tail surfactants is a suitable strategy to obtain low-viscosity surfactant-rich isotropic aqueous mixtures with negligible effects on biodegradability. This opens a way to the design of concentrated ("water-free") surfactant formulations, highly attractive for their ecological and economic benefits.

EXPERIMENTS

The aggregation behaviour of N,N-dimethyl-2-propylheptan-1-amine oxide (C₁₀DAO-branched) in aqueous mixtures is investigated across the entire composition range by polarized optical microscopy, small angle X-ray and neutron scattering, electron paramagnetic resonance, and pulse-gradient stimulated echo nuclear magnetic resonance. The humidity scanning quartz crystal microbalance with dissipation monitoring technique is validated as a tool for the fast screening of surfactants phase behaviour. Furthermore, the shear viscosities and viscoelastic moduli of the systems are determined by rheological measurements.

FINDINGS

With respect to the linear isomer, C₁₀DAO-branched presents a much lower tendency to form lyotropic liquid crystalline phases. Except for a narrow composition and temperature range in which a lamellar structure is observed, C₁₀DAO-branched aqueous mixtures are isotropic liquids whose microstructure changes, with increasing concentration, from micellar solutions to unstructured dispersions of hydrated surfactant molecules. Low-viscosity was found for all these mixtures, including the most concentrated ones. Thus, the introduction of a single short side-chain in the tail is demonstrated to be an effective approach to increase the active concentration in surfactant formulations.

Facile Fabrication of an Amentoflavone-Loaded Micelle System for Oral Delivery To Improve Bioavailability and Hypoglycemic Effects in KKAy Mice

In order to increase the oral bioavailability and antidiabetic effect of amentoflavone with multimechanisms, an oral micelle system was developed by using a N-vinyl pyrrolidone-maleate-guerbet alcohol monoester polymer for the first time, which was designated as P(NVP-MGAM)/AF. After oral administration, P(NVP-MGAM)/AF enhanced the oral bioavailability of amentoflavone, which was approximately 3.2 times that of amentoflavone solution. The animal study using the KKAy insulin-resistant diabetes mouse model indicated that it regulates the expression and activity of downstream signaling factors and proteins by lowering blood lipids, reducing inflammatory responses and activating the peroxisome proliferator-activated receptor (PPAR) γ signaling pathway and PI3K/Akt signaling pathway. After being made into micelles, it is more effective because of its better absorbability and bioavailability. The results from this study provide a theoretical basis for the clinical application of amentoflavone for diabetes treatment. The oral micelles of P(NVP-MGAM)/AF may become one of the most potent drugs in the treatment of diabetes mellitus, which opens up a new way for the prevention and treatment of diabetes.

Preparation of membrane-mimicking lamellar structures by molecular confinement of hybrid nanocomposites

Hybrid nanocomposites are multiphase systems with a wide range of applications. Some nanocomposites are water insoluble thereby preventing several applications. Thus, we prepared telechelic PEO with glucose molecules to form water-soluble lamellar nanostructures by co-assembly with metallacarborane. The lamellas formed by PEO/metallacarborane decorated by glucose molecules on the surface can serve as delivery agents for boron clusters and benzoxaboroles.