《Molecular Hydrogels from Bolaform Amino Acid Derivatives: A Structure-Properties Study Based on the Thermodynamics of Gel Solubilization》 was published in Chemistry – A European Journal in 2012. These research results belong to Nebot, Vicent J.; Armengol, Jose; Smets, Johan; Prieto, Susana Fernandez; Escuder, Beatriu; Miravet, Juan F.. COA of Formula: C11H9N3O The article mentions the following:
Insight is provided into the aggregation thermodn. associated with hydrogel formation by mol. gelators derived from L-valine and L-isoleucine. Solubility data from NMR measurements are used to extract thermodn. parameters for the aggregation in water. At room temperature and up to 55°C, these systems form self-assembled fibrillar networks in water with quite low or zero enthalpic component, whereas the entropy of the aggregation is favorable. These results are explained by considering that the hydrophobic effect is dominant in the self-assembly. However, studies by NMR and IR spectroscopy reveal that intermol. hydrogen bonding is also a key issue in the aggregation process of these mols. in water. The low enthalpy values measured for the self-assembly process are ascribed to the result of a compensation of the favorable intermol. hydrogen-bond formation and the unfavorable enthalpy component of the hydrophobic effect. Addnl., by using the hydrophobic character as a design parameter, enthalpy-controlled hydrogel formation, as opposed to entropy-controlled hydrogel formation, can be achieved in water if the gelator is polar enough. It is noteworthy that these two types of hydrogels, enthalpy- vs. entropy-driven hydrogels, present quite different response to temperature changes in properties such as the min. gelator concentration or the rheol. moduli. Finally, the presence of a polymorphic transition in a hydrogel upon heating above 70°C is reported and ascribed to the weakening of the hydrophobic effect upon heating. The new soft polymorphic materials present dramatically different solubility and rheol. properties. Altogether these results are aimed to contribute to the rational design of mol. hydrogelators, which could be used for the tailored preparation of this type of soft materials. The reported results could also provide ground for the rationale of different self-assembly processes in aqueous media. The experimental process involved the reaction of N-(Pyridin-4-yl)isonicotinamide(cas: 64479-78-3COA of Formula: C11H9N3O)
N-(Pyridin-4-yl)isonicotinamide(cas: 64479-78-3) belongs to amides. Because of the greater electronegativity of oxygen, the carbonyl (C=O) is a stronger dipole than the N–C dipole.COA of Formula: C11H9N3O The presence of a C=O dipole and, to a lesser extent a N–C dipole, allows amides to act as H-bond acceptors. In primary and secondary amides, the presence of N–H dipoles allows amides to function as H-bond donors as well.
Referemce:
Amide – Wikipedia,
Amide – an overview | ScienceDirect Topics