Facile Syntheses of a Class of Supramolecular Gelator Following a Combinatorial Library Approach: Dynamic Light Scattering and Small-Angle Neutron Scattering Studies (original) (raw)
Related papers
Influence of solvent on the supramolecular architectures in molecular gels
Soft Matter, 2013
Elucidating the molecular structures, responsible for promoting self-assembly of low-molecular weight organogelators (LMOG) into supramolecular fibers, has been an extensive area of study. Although this has been a fruitful endeavor, this study illustrates that the chemical nature of the solvent and solventgelator interactions are equally important. The nanostructure, microstructure and supramolecular structures, of 12HSA molecules gels, are all influenced by the chemical nature of the solvent, which correlate to the hydrogen-bonding Hansen solubility parameter (v h ). Depending on the solvent employed, the polymorphic form, arrangement of the carboxylic acid dimers, domain size, fiber morphology, microstructure, thermal properties and visual appearance of the gel all differ. Solvents that have d h < 4.4 MPa 1/2 , result in a hexagonal polymorphic form, with an 001 hlk spacing greater than the extended bi-molecular length of 12HSA. This nanoscale arrangement results in translucent gels that contain fibrillar aggregates corresponding to a higher crystallinity compared to molecular gels formed in solvents that have a d h > 4.4 MPa 1/2 .
Journal of Organic Chemistry, 2009
The supramolecular synthon approach has been employed to synthesize noncovalently a series of low molecular mass organic gelators (LMOGs) derived from benzylammonium salts of variously substituted benzoic acids. The majority of the salts (75%) prepared showed interesting gelation properties. Instant gelation of an organic fluid, namely methyl salicylate, was achieved at room temperature by using most of the gelator salts by in situ synthesis of the gelators. rheology and scanning electron microscopy (SEM) were used to characterize the gels. Single crystal X-ray diffraction studies revealed the presence of both 1D and 2D supramolecular synthons. X-ray powder diffraction (XRPD) studies indicated the presence of various crystalline phases in the fibers of the xerogels. By using these data, a structure-property correlation has been attempted and the working hypothesis for designing the gelator has been reinforced.
Multi-purpose gel : from supramolecular envirogel to high-value applications
2015
Dibenzylidene-D-sorbitol (DBS) has remained a well-known low molecular weight gelator of organic solvents for over 100 years. As such, it constitutes a very early example of supramolecular gels. It has found widespread applications such as personal care products and high-tech applications. Despite the versatility of DBS as an organogelator and industrial feedstock, none of its existing derivatives could gel water. Herein, functionalization of the aromatic ‘wings’ with various functionalities and their gelation profiles were described. None of the synthesized derivatives but DBS-COOH and DBS-CONHNH2 could undergo gelation in water. DBS-COOH formed a stable hydrogel by pH-switching while the DBS-CONHNH2 formed stable hydrogels across a wide range of pH values by a heat-cool cycle. CD spectroscopy and SEM were used to show that these functionalities control the aggregation mode of the parent DBS. DBS-COOH and DBS-CONHNH2 hydrogels demonstrated a significant uptake of dyes from model po...
Organic & Biomolecular Chemistry, 2010
Au-NAC and Ag-NAC hydrogels were dissolved by the addition of NaOH 1N and the resulting solutions were dialysed against ultrapure water for 3 days. Then, the solutions were freeze-dried to give the corresponding compounds as white solids. Cu-NAC was unstable to dialysis and it was purified as follows: the gel was diluted in HCl 0.001 N. The resulting suspension was then centrifuged and washed several times with HCl 0.001 N. The product was lyophilised to give Cu-NAC as a white solid. Energy dispersive X-ray spectroscopy (EDS) Analyses were performed on an INCA-300 model from OXFORD, operated at an accelerating voltage of 20 kV.
Physicochemical Properties and the Gelation Process of Supramolecular Hydrogels: A Review
Gels, 2017
Supramolecular polysaccharide-based hydrogels have attracted considerable research interest recently due to their high structural functionality, low toxicity, and potential applications in foods, cosmetics, catalysis, drug delivery, tissue engineering and the environment. Modulation of the stability of hydrogels is of paramount importance, especially in the case of stimuli-responsive systems. This review will update the recent progress related to the rational design of supramolecular hydrogels with the objective of understanding the gelation process and improving their physical gelation properties for tailored applications. Emphasis will be given to supramolecular host-guest systems with reference to conventional gels in describing general aspects of gel formation. A brief account of the structural characterization of various supramolecular hydrogels is also provided in order to gain a better understanding of the design of such materials relevant to the nature of the intermolecular interactions, thermodynamic properties of the gelation process, and the critical concentration values of the precursors and the solvent components. This mini-review contributes to greater knowledge of the rational design of supramolecular hydrogels with tailored applications in diverse fields ranging from the environment to biomedicine.
Solvent effect on the morphology and function of novel gel-derived molecular materials
Journal of Materials Chemistry, 2010
The gelation of two distinct hydrocarbon solvents by a new p-functional molecule, followed by doping and measurement of conducting properties of the derived xerogel, reveals an important effect of the main gel component on the shape and organisation of the supramolecular fibres formed by the aromatic moieties. The gelator-a tetrathiafulvalene (TTF) derivative with two hydrophobic chains incorporating amide groups near the aromatic group-was also cast onto hydrophobic and hydrophilic surfaces from homogeneous solution and shows the dramatic influence of the concentration and surface on the aggregate formation, as revealed by atomic force microscopy (AFM). This observation underlines the advantage of using the gel route to prepare films of these materials. The doped xerogels show the effect of the solvent at the microscopic and macroscopic levels, as revealed by current sensing AFM and bulk four point conductivity measurements. The real polymorphism of the xerogels was confirmed by electron paramagnetic resonance (EPR) spectroscopy. In both materials, prepared from gels in (S)-limonene and n-hexane, and in contrast to a related compound with one hydrogen bonding group, the double hydrogen bond motif leads to materials which do not show structural phase transitions when heated. This feature shows the potential benefit of incorporating several hydrogen bonding groups on the phase stability of gel derived materials; to stabilise the metastable states to produce materials with different properties from a single compound by processing in different solvents.
Time-dependent gel to gel transformation of a peptide based supramolecular gelator
Soft Matter, 2015
A dipeptide with a long fatty acid chain at its N-terminus gives hydrogels in phosphate buffer in the pH range 7.0-8.5. The hydrogel with a gelator concentration of 0.45% (w/v) at pH 7.46 (physiological pH) provides a very good platform to study dynamic changes within a supramolecular framework as it exhibits remarkable change in its appearance with time. Interestingly, the first formed transparent hydrogel gradually transforms into a turbid gel within 2 days. These two forms of the hydrogel have been thoroughly investigated by using small angle X-ray scattering (SAXS), powder X-ray diffraction (PXRD), field emission scanning electron microscopic (FE-SEM) and high-resolution transmission electron microscopic (HR-TEM) imaging, FT-IR and rheometric analyses. The SAXS and low angle PXRD studies substantiate different packing arrangements for the gelator molecules for these two different gel states (the freshly prepared and the aged hydrogel). Moreover, rheological studies of these two gels reveal that the aged gel is stiffer than the freshly prepared gel.