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Cooperativity of the Assembly Process in a Low Concentration Chromonic Liquid Crystal

Cooperativity of the Assembly Process in a Low Concentration Chromonic Liquid Crystal

Benjamin R Mercado, Kenneth J Nieser, Peter J Collings

J Phys Chem B. 2014 Nov 20;118(46):13312-20.

PMID: 25365417

Abstract:

IR-806 is a near-infrared cyanine dye that undergoes a two-step assembly process in aqueous solutions. The final assemblies orientationally order into a liquid crystal at a very low concentration (∼0.6 wt % at room temperature). While the first step of the assembly process is continuous as the dye concentration or temperature is varied (isodesmic), the second step is more abrupt (cooperative). Because the absorption spectrum of IR-806 changes dramatically during the assembly process, careful equilibrium and kinetic absorption experiments are utilized to examine the details of the cooperative second step. These experiments involve changes in both concentration and temperature, allowing a close thermodynamic analysis of the assembly process. Both equilibrium and kinetic investigations reveal that the assembly process is highly cooperative and can be described by multiple models (for example, nucleation and growth) in the highly cooperative limit. The enthalpy associated with the growth process and the activation energy of the rate-limiting step during disassembly are determined. These findings have significant implications for the structure of the assemblies that form the liquid crystal phase in IR-806.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
LS77556	IR-806			Price

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