Structural optimization of super-gelators derived from naturally-occurring mannose and their morphological diversity

Abstract

Mannose derivatives were synthesized as low molecular-weight gelators with various alkoxy substituents on the aromatic ring of methyl-4,6-O-benzilidene-a-D-mannopyranoside . Most of these mannose derivatives could gel in various solvents, such as octane, cyclohexane, toluene, ethylene glycol and ethanol solutions, at concentrations lower than 2.0 wt%. In particular, the critical gelation concentration (CGC) of methyl-4,6-O-(4-butoxybenzylidene)-a-D-mannopyranoside (2) for squalane was only 0.025 wt%, one of the lowest CGCs we have ever experienced. The observations of xerogels by FE-SEM, TEM and AFM revealed that the length of the alkoxy chains of the mannose derivatives influences the gel morphologies. Moreover, the toluene gels formed from the mannose derivatives 1-6 functionalized by a linear alkoxy group exhibited thixotropic properties. Interestingly, the gels of various solvents formed from methyl-4,6-O-(4dodecyloxybenzylidene)-a-D-mannopyranoside (6) (with the longest alkoxy chain on the aromatic ring in this paper) exhibited thixotropic properties. Thus, we confirmed that alkoxy groups on the aromatic ring exert noticeable effects on the gelation properties of these mannose derivatives.

Lipase‐Catalyzed Synthesis of Substituted Phenylacetamides: Hammett Analysis and Computational Study of the Enzymatic Aminolysis

“…LMWGs of 4,6‐benzylidene monosaccharides were first reported by Shinkai and co‐workers in 1998,47 and since then a number of 4,6‐benzylidene‐glycoside‐type gelators have been studied 48–55. Recently, we reported the gelation ability of 4,6‐benzylidene mannose derivatives, which were able to gel various organic solvents and aqueous solutions 56. It is particularly worth noting that the critical gelation concentration (CGC) of the 4,6‐( p ‐butoxybenzylidene)‐mannose derivative in squalane was 0.025 wt.‐%.…”

“…Gelator 3a in the hydrogel therefore adopts a one‐dimensional arrangement with interdigitation of the gelator molecules with the overlap of their alkoxy chains driven by van der Waals interactions. We previously reported that the self‐assembly modes of the 4,6‐benzylidene mannose derivative were different in the organogel and the hydrogel with the major driving forces being hydrogen‐bonding interactions in the organogel and van der Waals interactions in the hydrogel 56. Interestingly, the PXRD pattern of the hydrogel of the mannose derivative reveals periodic diffraction peaks corresponding to hexagonal packing, whereas that of the hydrogel of the glucose derivative 3a reveals simple peaks, as in the case of the organogel.…”

Mild One‐Step Synthesis of 4,6‐Benzylideneglycopyranosides from Aromatic Aldehydes and Gelation Abilities of the Glucose Derivatives

“…We previously reported that the self-assembly modes of the 4,6-benzylidene mannose derivative were different in the organogel and the hydrogel with the major driving forces being hydrogen-bonding interactions in the organogel and van der Waals interactions in the hydrogel. [56] Interestingly, the PXRD pattern of the hydrogel of the mannose derivative reveals periodic diffraction peaks corresponding to hexagonal packing, whereas that of the hydrogel of the glucose derivative 3a reveals simple peaks, as in the case of the organogel. As a result, the hydrogel and organogel prepared from 3a consist of very thin supple fibrous networks.…”

“…[48][49][50][51][52][53][54][55] Recently, we reported the gelation ability of 4,6-benzylidene mannose derivatives, which were able to gel various organic solvents and aqueous solutions. [56] It is particularly worth noting that the critical gelation concentration (CGC) of the 4,6-(p-butoxybenzylidene)mannose derivative in squalane was 0.025 wt.-%. In this paper, we describe the gelation abilities of several glucoside derivatives in various solvents, including water.…”

Investigating hydrogel formation using in situ variable-temperature scanning probe microscopy

“… 3 These potential applications, which include drug delivery, tissue engineering, smart materials, crystal growth control, and sensors, 1 , 4 will be most efficiently developed if there is a robust understanding of the self-assembly and disassembly processes that take place during gel–sol transitions. To date, characterisation of gel structures has typically relied on imaging of dried gel samples using electron or scanning probe microscopy, 5 or the typically lower resolution option of confocal laser microscopy of “wet” gels. 6 A significant concern is the introduction of artefacts during drying processes, although it is possible to correlate microscopy results with X-ray or neutron scattering data to determine if dramatic changes have occurred.…”