Constitutive framework for biodegradable polymers with applications to biodegradable stents.

Area of Science:

• Materials Science
• Biomedical Engineering
• Polymer Physics

Background:

• Biodegradable polymeric stents require sustained mechanical support during artery healing.
• Cyclic loading influences the degradation rate and mechanical properties of these polymers.
• Understanding polymer behavior under load is critical for stent design and efficacy.

Purpose of the Study:

• To develop a theoretical framework for studying deformation-induced degradation in polymers.
• To model the relationship between mechanical stress, degradation, and material softening.

Main Methods:

• Developed a constitutive model for polymers exhibiting deformation-induced degradation.
• Introduced a scalar field to represent the local degradation state.
• Coupled a strain-dependent degradation rate equation with the balance of linear momentum.

Main Results:

• The model predicts stress relaxation, creep, and hysteresis in polymers under uniaxial extension.
• Degradation, characterized by bond scission and molecular weight reduction, leads to material softening.
• The theoretical framework captures the interplay between mechanical loading and polymer degradation.

Conclusions:

• The proposed constitutive model provides a robust theoretical basis for analyzing biodegradable polymers.
• This framework is essential for predicting the long-term performance and safety of biodegradable medical devices.
• Further experimental validation will enhance the model's applicability in real-world stent applications.