Programmed water-induced shape-memory of bioabsorbable poly(D,L-lactide): activation and properties in physiological...

Area of Science:

• Polymer Science
• Biomaterials Engineering
• Materials Science

Background:

• Bioabsorbable polymers are crucial for medical devices.
• Existing shape-memory polymers often require external stimuli or complex synthesis.
• Developing intrinsic shape-memory in bioabsorbable materials is highly desirable.

Purpose of the Study:

• To report a novel water-induced shape-memory effect in bioabsorbable poly(D,L-lactide).
• To develop and characterize an orientation-based programming process for this shape-memory functionality.
• To investigate the influence of sterilization on shape-memory properties.

Main Methods:

• Deforming and orienting poly(D,L-lactide) at elevated temperatures, followed by cooling to lock the shape.
• Activating shape-memory in a 37°C aqueous environment.
• Assessing shape-recovery ratio and rate, and stress generation/relaxation.
• Investigating the effect of gamma (γ) irradiation on shape-memory properties.

Main Results:

• The orientation-programming process enables shape transformation at 37°C in water without external energy.
• Water molecules plasticize the polymer, reducing the glass transition temperature by 10-13°C, activating shape-memory.
• Both non-γ-irradiated and γ-irradiated samples showed excellent shape-recovery ratios (94% and 97%) over ten weeks.
• Materials generated predefined loads or adapted to stress relaxation when shape-recovery was restricted or external tension was applied.

Conclusions:

• A novel, water-induced shape-memory effect was successfully generated in bioabsorbable poly(D,L-lactide) via orientation programming.
• This method allows shape-memory functionality without altering the polymer's chemical structure, accelerating medical device development.
• The process is robust, with sterilization (γ-irradiation) affecting recovery rate but not the recovery ratio, maintaining high performance over time.