Eclipsed conformational locking: exploring iota carrageenan’s distinct behavior in ethanol–water systems via hydrogen bonding with the disulfate group

Abstract

The present investigation combines diverse experimental methodologies with meticulous examination of the alterations throughout the technique and sheds new light on the interaction between iota carrageenan and ethanol. The interaction of ethanol and iota-carrageenan gives an unstable conformer (eclipsed) with the help of interaction between the disulfate and hydroxy group, which gives the soluble solution phase instead of gel from. The results regarding the interaction between disulfate and ethanol confirm the essential role of disulfate, and the alteration in the physical characteristic of ethanol further substantiates the presence of hydrogen bonding, as evidenced by the widening of the infrared peak of C–O–S (710–720 cm⁻¹), S–O (1100 cm⁻¹); moreover, the broadening of the peak corresponds to the S=O strongly suggests the interaction with ethanol through hydrogen bonding. The interaction of the carrageenan and ethanol was also confirmed by the evaporation process, which suggests the 20% reduction in the volume of ethanol where iota carrageenan was added; however, in case of kappa, the volume reduction was 60%. In addition to that, the microscopic analysis of the carrageenan and ethanol also supports the possibility of interaction and role of disulfate in the interaction. The solution phase of carrageenan can be utilized further for the chemical reaction for the functionalization and grafting, while in most of the solvent it remains in insoluble form or in gel form, which does not provide a homogenous system to molecule colloids for the reaction.