Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators

The structural modification of existing supramolecular architecture is an efficient strategy to design and synthesize supramolecular gels with tunable and predictable properties. In this work, we have modified bis(pyridyl urea) compounds with different linkers, namely hexylene and butylene, to their...

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Autores principales:	Sreejith Sudhakaran Jayabhavan, Dipankar Ghosh, Krishna K. Damodaran
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	LMWGs stimuli-responsive structural modification pyridyl urea pyridyl-<i>N</i>-oxide Organic chemistry QD241-441
Acceso en línea:	https://doaj.org/article/7a15770fa5e74757a19280ac059dc364
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spelling	oai:doaj.org-article:7a15770fa5e74757a19280ac059dc3642021-11-11T18:26:26ZMaking and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators10.3390/molecules262164201420-3049https://doaj.org/article/7a15770fa5e74757a19280ac059dc3642021-10-01T00:00:00Zhttps://www.mdpi.com/1420-3049/26/21/6420https://doaj.org/toc/1420-3049The structural modification of existing supramolecular architecture is an efficient strategy to design and synthesize supramolecular gels with tunable and predictable properties. In this work, we have modified bis(pyridyl urea) compounds with different linkers, namely hexylene and butylene, to their corresponding bis(pyridyl-<i>N</i>-oxide urea). The gelation properties of both the parent and the modified compounds were studied, and the results indicated that modification of the 3-pyridyl moieties to the corresponding 3-pyridyl-<i>N</i>-oxides induced hydrogelation. The stability of the parent and modified compounds were evaluated by sol-gel transition temperature (<i>T<sub>gel</sub></i>) and rheological measurements, and single-crystal X-ray diffraction was used to analyze the solid-state interactions of the gelators. The morphologies of the dried gels were analyzed by scanning electron microscopy (SEM), which revealed that the structural modification did not induce any prominent effect on the gel morphology. The stimuli-responsive behavior of these gels in the presence of salts in DMSO/water was evaluated by rheological experiments, which indicated that the modified compounds displayed enhanced gel strength in most cases. However, the gel network collapsed in the presence of the chloride salts of aluminum(III), zinc(II), copper(II), and cadmium(II). The mechanical strength of the parent gels decreased in the presence of salts, indicating that the structural modification resulted in robust gels in most cases. The modified compounds formed gels below minimum gel concentration in the presence of various salts, indicating salt-induced gelation. These results show the making and breaking ability of the gel network in the presence of external stimuli (salts), which explains the potential of using LMWGs based on <i>N</i>-oxide moieties as stimuli-responsive materials.Sreejith Sudhakaran JayabhavanDipankar GhoshKrishna K. DamodaranMDPI AGarticleLMWGsstimuli-responsivestructural modificationpyridyl ureapyridyl-<i>N</i>-oxideOrganic chemistryQD241-441ENMolecules, Vol 26, Iss 6420, p 6420 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	LMWGs stimuli-responsive structural modification pyridyl urea pyridyl-<i>N</i>-oxide Organic chemistry QD241-441
spellingShingle	LMWGs stimuli-responsive structural modification pyridyl urea pyridyl-<i>N</i>-oxide Organic chemistry QD241-441 Sreejith Sudhakaran Jayabhavan Dipankar Ghosh Krishna K. Damodaran Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators
description	The structural modification of existing supramolecular architecture is an efficient strategy to design and synthesize supramolecular gels with tunable and predictable properties. In this work, we have modified bis(pyridyl urea) compounds with different linkers, namely hexylene and butylene, to their corresponding bis(pyridyl-<i>N</i>-oxide urea). The gelation properties of both the parent and the modified compounds were studied, and the results indicated that modification of the 3-pyridyl moieties to the corresponding 3-pyridyl-<i>N</i>-oxides induced hydrogelation. The stability of the parent and modified compounds were evaluated by sol-gel transition temperature (<i>T<sub>gel</sub></i>) and rheological measurements, and single-crystal X-ray diffraction was used to analyze the solid-state interactions of the gelators. The morphologies of the dried gels were analyzed by scanning electron microscopy (SEM), which revealed that the structural modification did not induce any prominent effect on the gel morphology. The stimuli-responsive behavior of these gels in the presence of salts in DMSO/water was evaluated by rheological experiments, which indicated that the modified compounds displayed enhanced gel strength in most cases. However, the gel network collapsed in the presence of the chloride salts of aluminum(III), zinc(II), copper(II), and cadmium(II). The mechanical strength of the parent gels decreased in the presence of salts, indicating that the structural modification resulted in robust gels in most cases. The modified compounds formed gels below minimum gel concentration in the presence of various salts, indicating salt-induced gelation. These results show the making and breaking ability of the gel network in the presence of external stimuli (salts), which explains the potential of using LMWGs based on <i>N</i>-oxide moieties as stimuli-responsive materials.
format	article
author	Sreejith Sudhakaran Jayabhavan Dipankar Ghosh Krishna K. Damodaran
author_facet	Sreejith Sudhakaran Jayabhavan Dipankar Ghosh Krishna K. Damodaran
author_sort	Sreejith Sudhakaran Jayabhavan
title	Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators
title_short	Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators
title_full	Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators
title_fullStr	Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators
title_full_unstemmed	Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators
title_sort	making and breaking of gels: stimuli-responsive properties of bis(pyridyl-<i>n</i>-oxide urea) gelators
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/7a15770fa5e74757a19280ac059dc364
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Making and Breaking of Gels: Stimuli-Responsive Properties of Bis(Pyridyl-<i>N</i>-oxide Urea) Gelators

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