Model study for large deformation of physical polymeric gels.

Area of Science:

• Polymer Science
• Materials Science
• Rheology

Background:

• Polymer gels exhibit complex mechanical behaviors, including strain hardening and softening, under large deformations.
• Understanding the role of physical cross-linking and chain dynamics is crucial for predicting gel properties.

Purpose of the Study:

• To develop a theoretical model for large deformation of polymer gels with physical cross-linking.
• To investigate the relationship between chain unravelling, dangling chains, and macroscopic mechanical responses.

Main Methods:

• Development of a physical model incorporating coil-helix transition equilibrium and end-to-end distance distribution.
• Analysis of stress-strain curves to validate model predictions against experimental data.

Main Results:

• The model accurately predicts experimental stress-strain curves, showing strain hardening followed by strain softening.
• The distribution of end-to-end distance significantly impacts yield behavior and strain softening.
• Dangling chains, formed by chain unravelling, are identified as the cause of strain softening.

Conclusions:

• The developed model provides a mechanistic understanding of large deformation in polymer gels.
• Physical cross-linking and chain unravelling are key factors governing the mechanical response and failure mechanisms.
• The model offers a predictive framework for designing polymer gels with tailored mechanical properties.