Viscoelastic Behavior of Aqueous Hydroxypropyl Cellulose Solutions Due to Entanglements

Area of Science:

• Polymer Science
• Rheology
• Materials Science

Background:

• Hydroxypropyl cellulose (HpC) is known to form liquid crystalline phases in aqueous solutions.
• HpC is presumed to possess a rod-like molecular conformation in these solutions.
• Understanding the rheological behavior of HpC solutions is crucial for its applications.

Purpose of the Study:

• To investigate the viscoelastic behaviors of aqueous hydroxypropyl cellulose (HpC) solutions.
• To analyze the influence of concentration (c) and weight-average molar mass (Mw) on HpC solution rheology.
• To interpret the observed viscoelastic properties using the framework of rod particle suspension rheology.

Main Methods:

• Examined viscoelastic behaviors of HpC solutions with varying molar substitution (MS ≈ 3.8) and weight-average molar masses (Mw = 36–740 kg mol⁻¹).
• Conducted rheological measurements over a wide concentration range (c).
• Utilized dilute solution properties to determine number density (ν), intrinsic viscosity, and average rod particle length.

Main Results:

• Characterized the concentration and Mw dependencies of viscoelastic parameters like zero-shear viscosity, average relaxation time, and steady-state compliance.
• Observed these dependencies in the concentration range where HpC molecules become fully entangled.
• Established relationships between rheological parameters and molecular characteristics.

Conclusions:

• The viscoelastic properties of aqueous HpC solutions are well-described by rod particle suspension rheology.
• The study provides insights into the relationship between molecular architecture and macroscopic rheological behavior.
• Findings contribute to the understanding of liquid crystalline polymers in solution.