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Article

Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification

1
Department of Chemistry, Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavík, Iceland
2
Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK
*
Author to whom correspondence should be addressed.
Molecules 2019, 24(19), 3472; https://doi.org/10.3390/molecules24193472
Received: 31 August 2019 / Revised: 22 September 2019 / Accepted: 24 September 2019 / Published: 25 September 2019
(This article belongs to the Special Issue Supramolecular Gel)
The factors affecting the self-assembly process in low molecular weight gelators (LMWGs) were investigated by tuning the gelation properties of a well-known gelator N-(4-pyridyl)isonicotinamide (4PINA). The N―H∙∙∙N interactions responsible for gel formation in 4PINA were disrupted by altering the functional groups of 4PINA, which was achieved by modifying pyridyl moieties of the gelator to pyridyl N-oxides. We synthesized two mono-N-oxides (INO and PNO) and a di-N-oxide (diNO) and the gelation studies revealed selective gelation of diNO in water, but the two mono-N-oxides formed crystals. The mechanical strength and thermal stabilities of the gelators were evaluated by rheology and transition temperature (Tgel) experiments, respectively, and the analysis of the gel strength indicated that diNO formed weak gels compared to 4PINA. The SEM image of diNO xerogels showed fibrous microcrystalline networks compared to the efficient fibrous morphology in 4PINA. Single-crystal X-ray analysis of diNO gelator revealed that a hydrogen-bonded dimer interacts with adjacent dimers via C―H∙∙∙O interactions. The non-gelator with similar dimers interacted via C―H∙∙∙N interaction, which indicates the importance of specific non-bonding interactions in the formation of the gel network. The solvated forms of mono-N-oxides support the fact that these compounds prefer crystalline state rather than gelation due to the increased hydrophilic interactions. The reduced gelation ability (minimum gel concentration (MGC)) and thermal strength of diNO may be attributed to the weak intermolecular C―H∙∙∙O interaction compared to the strong and unidirectional N―H∙∙∙N interactions in 4PINA. View Full-Text
Keywords: LMWGs; hydrogel; structural modification; pyridyl amides; N-oxides LMWGs; hydrogel; structural modification; pyridyl amides; N-oxides
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MDPI and ACS Style

Ghosh, D.; Mulvee, M.T.; Damodaran, K.K. Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification. Molecules 2019, 24, 3472. https://doi.org/10.3390/molecules24193472

AMA Style

Ghosh D, Mulvee MT, Damodaran KK. Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification. Molecules. 2019; 24(19):3472. https://doi.org/10.3390/molecules24193472

Chicago/Turabian Style

Ghosh, Dipankar, Matthew T. Mulvee, and Krishna K. Damodaran 2019. "Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification" Molecules 24, no. 19: 3472. https://doi.org/10.3390/molecules24193472

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