Processing and properties of two different poly (ortho esters)

Area of Science:

• Polymer Science
• Biomaterials Engineering
• Materials Science

Background:

• Poly(ortho esters) (POEs) are a class of biodegradable polymers with potential applications in biomedical fields.
• Understanding the processing, properties, and in vitro behavior of novel POE structures is crucial for their development.

Purpose of the Study:

• To compare the processing and in vitro behavior of two structurally distinct poly(ortho esters).
• To evaluate the mechanical properties and degradation profiles of these POEs under various conditions.
• To assess the suitability of these POEs for applications such as bone fixation and tissue engineering.

Main Methods:

• Two POEs were synthesized: one a copolymer with polyacetal, the other with trans-cyclohexanedimethanol-dilactide.
• Polymers were processed using ultrasonic molding and melt-extrusion, with some undergoing self-reinforcement via die-drawing.
• In vitro hydrolysis was conducted in phosphate buffer saline (PBS) and simulated body fluid (SBF) at 37°C, with mechanical testing and weight change analysis.

Main Results:

• Self-reinforcing significantly increased shear strength, bending strength, and modulus in extruded rods.
• In vitro degradation was faster in unchanged PBS compared to weekly changed PBS.
• Strength retention varied from 14 to 42 days; dry weight decreased after the first week.
• Crystallization occurred in SBF, while amorphous structures persisted in PBS; surface erosion was observed and processing-dependent.

Conclusions:

• Both POE types exhibited rapid in vitro degradation, with limited strength retention time.
• Processing methods significantly influenced mechanical properties and erosion behavior.
• Despite limitations in storage time, these POEs show promise for bone fixation and tissue engineering applications.