Fibrillar structure of methylcellulose hydrogels

Area of Science:

• Polymer Science
• Materials Science
• Biomaterials

Background:

• Aqueous methylcellulose (MC) solutions form hydrogels upon heating.
• The precise gelation mechanism and structure of MC hydrogels are not fully understood.
• Understanding MC gel structure is crucial for applications in food, pharmaceuticals, and drug delivery.

Purpose of the Study:

• To precisely quantify the fibrillar structure of aqueous methylcellulose (MC) hydrogels.
• To elucidate the gelation mechanism at the nanoscale.
• To correlate nanoscale fibrillar morphology with macro-scale properties like turbidity and rheology.

Main Methods:

• Cryogenic transmission electron microscopy (cryo-TEM) for real-space imaging of fibril morphology.
• Small-angle neutron scattering (SANS) for reciprocal-space structural analysis.
• Quantitative modeling using a flexible cylinder form factor to analyze SANS data.

Main Results:

• MC chains (MW 300,000 g/mol) form uniform fibrils (15 ± 2 nm diameter) upon heating.
• MC gels exhibit nanoscale heterogeneity in fibril density, consistent with optical turbidity.
• SANS data analysis confirmed fibrillar structures (14 ± 1 nm diameter) and revealed scattering behavior consistent with flexible cylinders.

Conclusions:

• A combination of cryo-TEM and SANS provides a comprehensive nanoscale understanding of MC hydrogel structure.
• The study precisely characterizes the uniform fibrillar morphology of MC hydrogels.
• The findings correlate nanoscale structural features with observed macro-scale properties, advancing the understanding of MC gelation.