Study of galactomannose interaction with solids using AFM, IR and allied techniques

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Polymer Science

Background:

• Guar gum (GG) and locust bean gum (LBG) are biodegradable galactomannose polysaccharides with diverse industrial uses.
• Limited understanding of polysaccharide-surface interactions hinders broader application of GG and LBG.
• Investigating adsorption mechanisms is crucial for optimizing their performance in various sectors.

Purpose of the Study:

• To elucidate the dominant forces governing the adsorption of guar gum (GG) and locust bean gum (LBG) onto talc surfaces.
• To differentiate between electrostatic, hydrophobic, and hydrogen bonding contributions to adsorption.
• To provide insights for enhanced utilization of these natural polymers.

Main Methods:

• Adsorption tests and isotherm modeling (Langmuir).
• Electrophoretic mobility measurements for surface charge analysis.
• Spectroscopic techniques (FTIR, fluorescence) to probe molecular interactions.
• Atomic Force Microscopy (AFM) and molecular modeling for structural and interaction analysis.

Main Results:

• Adsorption of GG and LBG on talc is independent of pH and ionic strength, indicating minimal electrostatic influence.
• Fluorescence spectroscopy showed no evidence of hydrophobic domain formation.
• Urea, a hydrogen bond disruptor, significantly reduced adsorption, supporting hydrogen bonding.
• FTIR and adsorption free energy analysis confirmed hydrogen bonding as the primary interaction mechanism.
• Molecular modeling revealed flat adsorption of polymers to maximize OH group contact.

Conclusions:

• Hydrogen bonding is the principal driving force for guar gum and locust bean gum adsorption onto talc.
• The galactose/mannose ratio influences polymer structure but not the dominant adsorption mechanism.
• Findings clarify adsorption behavior, enabling better control and application of these polysaccharides.