Dispersant and Protective Roles of Amphiphilic Poly(ethylene phosphate) Block Copolymers in Polyester/Bone Mineral...

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Orthopedic Engineering

Background:

• Biodegradable polymer composites are crucial for bone regeneration and orthopedic applications.
• Challenges in composite manufacturing include poor homogeneity and thermal degradation during melt processing.
• Bone mineral substitutes (BMS) like beta-tricalcium phosphate (βTCP) and carbonated hydroxyapatite (CAp) are key components.

Purpose of the Study:

• To fabricate and characterize poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) composites with βTCP and CAp using injection molding.
• To improve the compatibility and performance of these composites through the use of reactive block copolymers.
• To investigate the impact of these compatibilizers on composite homogeneity, mechanical properties, and thermal stability.

Main Methods:

• Injection molding was used to fabricate composites of PLLA/PCL with βTCP, hexagonal CAp (hCAp), and plate-like CAp (pCAp).
• Reactive block copolymers of PLLA-poly(tert-butyl ethylene phosphate) (C1) and PCL-poly(tert-butyl ethylene phosphate) (C2) were synthesized and incorporated.
• Formation of polyester-b-poly(ethylene phosphoric acid) (PEPA) compatibilizer and its chemical binding with pCAp were experimentally verified.

Main Results:

• pCAp-based composites exhibited superior mechanical and thermal characteristics, particularly PLLA with 25 wt% pCAp.
• Incorporation of 5 wt% polyester-b-PEPA compatibilizer significantly improved composite homogeneity and mechanical properties (strength, moduli).
• The compatibilizer also enhanced nucleation effects during crystallization and increased thermal stability, especially for PLLA-based composites.

Conclusions:

• Polyester-b-PEPA compatibilizers effectively enhance the homogeneity and mechanical performance of BMS-polymer composites.
• These compatibilizers facilitate chemical binding with bone mineral substitutes, leading to improved material characteristics.
• The developed composite materials show significant promise for advanced applications in bone surgery and orthopedics.