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Molecular weight between entanglements for κ- and ι-carrageenans in an ionic liquid
Jun-ichi Horinaka1, Yuhei Urabayashi1, Xiaochen Wang1
1Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo, Kyoto 615-8510, Japan.
International Journal of Biological Macromolecules
|June 10, 2014
Summary
This study determined the molecular weight between entanglements (Me) for kappa- and iota-carrageenans in concentrated solutions. Results show carrageenans have larger entanglement spacing than agarose, with sulfate groups having minimal impact on the entanglement network.
Area of Science:
- Polymer Science
- Materials Science
- Biochemistry
Background:
- Carrageenans are sulfated galactans widely used in food and pharmaceutical industries.
- Understanding their rheological properties, particularly entanglement networks, is crucial for material applications.
- Previous studies have not fully elucidated the role of molecular structure on entanglement in concentrated carrageenan solutions.
Purpose of the Study:
- To determine the molecular weight between entanglements (Me) for kappa- and iota-carrageenans.
- To investigate the influence of sulfate groups on the entanglement network of carrageenans.
- To compare the entanglement characteristics of carrageenans with non-sulfated galactans like agarose.
Main Methods:
- Examined concentrated solutions of kappa- and iota-carrageenans using 1-butyl-3-methylimidazolium acetate as a solvent.
- Measured dynamic viscoelasticity data at various temperatures.
- Applied the time-temperature superposition principle to obtain master curves and determine plateau moduli.
Main Results:
- Master curves showed typical flow and rubbery plateau zones, indicative of concentrated polymer solutions with entanglement coupling.
- Estimated the molecular weight between entanglements in the molten state (Me,melt) for kappa-carrageenan as 6.6×10^3 and iota-carrageenan as 7.2×10^3.
- Found that the 4-sulfate group in iota-carrageenan has minimal influence on the entanglement network.
- Carrageenans exhibited larger average spacing between entanglements compared to agarose.
Conclusions:
- The molecular weight between entanglements (Me) is a key parameter for understanding carrageenan rheology.
- The degree and position of sulfation do not significantly alter the entanglement characteristics of carrageenans.
- Carrageenans form less dense entanglement networks than agarose, suggesting differences in their solution behavior and applications.
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