Creation of Molecular Gel Materials Using Polyrotaxane-Derived Polymeric Organogelator.

Molecular gels, which are soft and flexible materials, are candidates for healthcare, cosmetic base, and electronic applications as new materials. In this study, a new polymeric organogelator bearing a polyrotaxane (PR) structure was developed and could induce the gelation of N',N″-dimethylformamide (DMF), a known solvent for dissolving polymeric materials and salts. Furthermore, the resulting DMF molecular gels exhibited thixotropic properties, observed by the inversion method using vials, which are essential for gel spreading. The scanning electron microscopy of the xerogels suggested that the gel-forming ability and thixotropic property of gels were imparted by the network of the laminated aggregates of thin layer material similar to those of other gels made of clay materials. This thin layer material would be formed by the aggregation of polymeric organogelators. The dynamic viscoelasticity measurements of the obtained gels revealed the stability and pseudo-thixotropic behaviors of the obtained gels, as well as a specific concentration effect on the mechanical behavior of the gels attributed to the introduction of the PR structure. Additionally, the preparation of the polymer organogelator/polymer composites was investigated to improve the mechanical properties via the filler effect induced by the agglomerates of organogelator. Moreover, the tensile tests confirmed that the introduction of the gelator enhanced the mechanical properties of the composites.

Creation of Polymer Hydrogelator/Poly(Vinyl Alcohol) Composite Molecular Hydrogel Materials.

Polymer hydrogels, including molecular hydrogels, are expected to become materials for healthcare and medical applications, but there is a need to create new functional molecular gels that can meet the required performance. In this paper, for creating new molecular hydrogel materials, the gel formation behavior and its rheological properties for the molecular gels composed of a polymer hydrogelator, poly(3-sodium sulfo-p-phenylene-terephthalamide) polymer (NaPPDT), and water-soluble polymer with the polar group, poly(vinyl alcohol) (PVA) in various concentrations were examined. Molecular hydrogel composites formed from simple mixtures of NaPPDT aqueous solutions (0.1 wt.%~1.0 wt.%) and PVA aqueous solutions exhibited thixotropic behavior in the relatively low concentration region (0.1 wt.%~1.0 wt.%) and spinnable gel formation in the dense concentration region (4.0 wt.%~8.0 wt.%) with 1.0 wt.% NaPPDT aq., showing a characteristic concentration dependence of mechanical behavior. In contrast, each single-component aqueous solution showed no such gel formation in the concentration range in the present experiments. No gel formation behavior was also observed when mixed with common anionic polymers other than NaPPDT. This improvement in gel-forming ability due to mixing may be due to the increased density of the gel's network structure composed of hydrogelator and PVA and rigidity owing to NaPPDT.

Development of Thixotropic Molecular Oleogels Comprising Alkylanilide Gelators by Using a Mixing Strategy.

Molecular oleogels have the potential to be used as materials in healthcare applications. However, their design and synthesis are complex, thus requiring simple and effective methods for their preparation. This paper reports on alkylanilides that are low molecular-weight organogelators, which when appropriately mixed with different alkyl chain lengths could result in the formation of mixed molecular gels that exhibit excellent gel-forming ability and mechanical properties. In addition, the single and mixed molecular organogel systems were found to be applicable as single and mixed molecular oleogel systems capable of gelling oils such as olive oil and squalane. This has been found to be true, especially in molecular oleogel systems consisting of squalane, which is used as solvents in healthcare. The mixed squalene-molecular oleogel systems showed an increase in the critical (minimum) gelation concentration from 1.0 to 0.1 wt.% in the single system and an improvement in the thixotropic behavior recovery time. The thixotropic behavior of the molecular oleogels in the mixed system was quantitatively evaluated through dynamic viscoelasticity measurements; however, it was not observed for the single-system molecular oleogels. Scanning electron microscopy of the xerogels suggested that this behavior is related to the qualitative improvement of the network owing to the refinement of the mesh structure. These mixed molecular oleogels, composed of alkylanilides displaying such thixotropic behavior, could be used as candidates for ointment-base materials in the healthcare field.

Analysis of the Physical Characteristics of an Anhydrous Vehicle for Compounded Pediatric Oral Liquids.

The paucity of suitable drug formulations for pediatric patients generates a need for customized, compounded medications. This research study was set out to comprehensively analyze the physical properties of the new, proprietary anhydrous oral vehicle SuspendIt® Anhydrous, which was designed for compounding pediatric oral liquids. A wide range of tests was used, including sedimentation volume, viscosity, droplet size after dispersion in simulated gastric fluid, microscopic examination and content uniformity measurements to evaluate the properties of the anhydrous vehicle. The results showed that the vehicle exhibited consistent physical properties under varying conditions and maintained stability over time. This can be attributed to the unique blend of excipients in its formulation, which not only maintain its viscosity but also confer thixotropic behavior. The unique combination of viscous, thixotropic and self-emulsifying properties allows for rapid redispersibility, sedimentation stability, accurate dosing, potential drug solubility, dispersion and promotion of enhanced gastrointestinal distribution and absorption. Furthermore, the vehicle demonstrated long-term sedimentation stability and content uniformity for a list of 13 anhydrous suspensions. These results suggest that the anhydrous oral vehicle could serve as a versatile base for pediatric formulation, potentially filling an important gap in pediatric drug delivery. Future studies can further investigate its compatibility, stability and performance with other drugs and in different clinical scenarios.

Polymeric Hydrogelator-Based Molecular Gels Containing Polyaniline/Phosphoric Acid Systems.

To expand the range of applications of hydrogels, researchers are interested in developing novel molecular hydrogel materials that have affinities for the living body and the ability to mediate electrical signals. In this study, a simple mixing method for creating a novel composite molecular gel is employed, which combines a hydrophilic conductive polymer, a polyaniline/phosphoric acid complex, and a polymer hydrogelator as a matrix. The composite hydrogel showed an improved gel-forming ability; more effective mechanical properties, with an increased strain value at the sol-gel transition point compared to the single system, which may be sufficient for paintable gel; and a better electrochemical response, due to the electrically conducting polyaniline component. These findings demonstrate the applicability of the new composite hydrogels to new potential paintable electrode materials.

Molecular design of amphiphiles for Microenvironment-Sensitive kinetically controlled gelation and their utility in probing alcohol contents.

Pyrene-laced 'fluorescent' amphiphiles have been designed with a C4-alkyl chain as 'hydrophobic spacer' and sugar moiety as hydrophilic residue. The amphiphile containing acetylacetohydrazide as a bridging unit (1) showed gel formation both in water and ethanol medium, while no gelation was observed with compound (2) with acetohydrazide as bridging unit. Accordingly, the self-assembly behavior of 1 was thoroughly investigated both in water and EtOH medium (as well as in their mixtures) in addition to their physicochemical properties. Though the gel formation kinetics was slower in water medium, the hydrogel showed superior mechanical strength (and thixotropic behavior) and improved thermal stability compared to the ethanolic gel. In water, the percolating H-bonding network with high cohesive force restricts the dynamics of the probe molecules, leading to some extent limited intermolecular interactions. However, hydrophobic interactions in water medium can result in the formation of rather 'compact' nano-assembly (H-type aggregation) with prominent π-π stacking interactions. Such unique solvent-dependency of 1 was further utilized to screen commercially available beverages in terms of their alcohol contents and probe adulteration in beverages. Besides, the hydrogel also showed excellent stimuli responsiveness, a gel-to-sol transition, accompanied by fluorescence color change, was observed in the presence of insulin.

Effects of Fumed Silica on Thixotropic Behavior and Processing Window by UV-Assisted Direct Ink Writing.

In this research, the effects of fumed silica (FS) on the Ultraviolet (UV)-ink rheological behavior and processing windows were discussed. Objects using different concentrations of FS inks were printed by the modified UV-Direct ink writing (DIW) printer. The function of fumed silica in the ink-based system has been verified, and the processing scope has been expended with a suitable amount of FS combined with the UV light. The results show that the combination of a suitable amount of FS with the UV-DIW system reaches fast and accurate printing with a larger processing window compared to the non-UV system. However, an excessively high concentration of FS will increase the yield stress of the ink, which also increases the requirement of extrusion unit and the die-swelling effects.

N-Alkylhydantoins as New Organogelators and Their Ability to Create Thixotropic Mixed Molecular Organogels.

The author reported molecular organogels using N-alkylhydantoins as new low-molecular-weight gelators for the first time, and thixotropic mixed molecular organogels using a set of N-alkylhydantoin gelators with different alkyl chain lengths. These homologous compounds with different alkyl chains are found to form macroscopic crystals or solution states in polar solvents, but form homogeneous organogels in non-polar solvents, such as n-octane and squalane. Although there is no significant increase in the minimum gelation concentration of the mixed molecular gels using squalane as a solvent, these mixed molecular organogels show improved mechanical properties, especially in their thixotropic behavior, which is not observed in the single N-alkylhydantoin gels. Furthermore, they exhibit reversible thixotropic behavior with quick recovery of the gel state in a minute by quantitatively measuring dynamic viscoelasticity measurements of rheometry of mixed molecular gels. Based on the morphological observations of the xerogels, the self-assembling fibers of the gelators become finer, indicating an increase in the density of the mesh structure inside the gel, which could explain its thixotropic behavior. These thixotropic mixed molecular gels may be applicable to ointment base materials, because they are gelled with squalane oil.

Extraction of Natural Gum from Cold-Pressed Chia Seed, Flaxseed, and Rocket Seed Oil By-Product and Application in Low Fat Vegan Mayonnaise.

This study involves the modeling of rheological behavior of the gum solution obtained from cold-pressed chia seed (CSG), flaxseed (FSG), and rocket seed (RSG) oil by-products and the application of these gums in a low-fat vegan mayonnaise formulation as fat replacers and emulsifier. CSG, FSG, and RSG solutions showed shear-thinning flow behavior at all concentrations. The K values ranged between 0.209 and 49.028 Pa·sn for CSG, FSG, and RSG solutions and significantly increased with increased gum concentration. The percentage recovery for the G' was significantly affected by gum type and concentrations. CSG, FSG, and RSG showed a solid-like structure, and the storage modulus (G') was higher than the loss modulus (G″) in all frequency ranges. The rheological characterization indicated that CSG, FSG, and RSG could be evaluated as thickeners and gelling agents in the food industry. In addition, the rheological properties, zeta potential, and particle size and oxidative stability (at 90 °C) of low-fat vegan mayonnaise samples prepared with CSG, FSG, and RSG were compared to samples prepared with guar gum (GG), Arabic gum (AG), and xanthan gum (XG). As a result, CSG, FSG, and RSG could be utilized for low-fat vegan mayonnaise as fat and egg replacers, stabilizers, and oxidative agents. The results of this study indicated that this study could offer a new perspective in adding value to flaxseed, chia seed, and rocket seed cold-press oil by-product.