Probing cellulose-solvent interactions with self-diffusion NMR: Onium hydroxide concentration and co-solvent effects
B Medronho1, A Pereira2, H Duarte2
1MED-Mediterranean Institute for Agriculture, Environment and Development, Universidade do Algarve, Faculdade de Ciências e Tecnologia, Campus de Gambelas, Ed. 8, 8005-139 Faro, Portugal; FSCN Research Center, Surface and Colloid Engineering, Mid Sweden University, SE-851 70 Sundsvall, Sweden.
Carbohydrate Polymers
|January 19, 2023
Summary
Researchers measured molecular diffusion in cellulose solutions using NMR. Results show tetrabutylammonium hydroxide (TBAH) ions bind to cellulose, influencing chain interactions and potentially hindering dissolution.
Area of Science:
- Polymer Science
- Physical Chemistry
- Materials Science
Background:
- Microcrystalline cellulose (MCC) dissolution is crucial for its applications.
- Understanding solvent-solute interactions in cellulose solutions is key to controlling its properties.
- Aqueous tetrabutylammonium hydroxide (TBAH) is a promising solvent system for cellulose.
Purpose of the Study:
- To investigate the molecular self-diffusion coefficients of cellulose solutions.
- To quantify the binding of ions and solvent molecules to cellulose.
- To elucidate the interaction mechanisms between cellulose, TBAH, and co-solvents.
Main Methods:
- Pulsed field gradient stimulated echo Nuclear Magnetic Resonance (NMR) measurements were employed.
- Solutions of microcrystalline cellulose in TBAH (aq) and TBAH (aq)/DMSO mixtures were analyzed.
- A two-state model was used to estimate binding parameters.
Main Results:
- Self-diffusion coefficients were determined for cellulose in various solvent compositions.
- The average number of TBA+ ions bound per anhydroglucose unit (AGU) ranged from 0.5 to 2.3.
- The fraction of bound molecules (Pb) for TBA+, DMSO, and water increased with cellulose concentration.
Conclusions:
- TBAH interacts with ionized hydroxyl groups on cellulose, forming a TBA+ counterion sheath.
- This interaction leads to steric hindrance between cellulose chains, impacting dissolution.
- The findings provide insights into the mechanism of cellulose dissolution in TBAH-based systems.
Keywords:
Cellulose dissolutionDimethylsulfoxideNuclear magnetic resonanceSelf-diffusionTetrabutylammonium hydroxideMore Related Videos
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