Modeling of Phase Separation and Growth in Immiscible Polymer Blends for Fabrication of High-Strength Medical Implants

Polyether ether ketone (PEEK) is a biocompatible high-strength polymer that has been receiving growing attention for bone implant applications. However, the chemical inertness of PEEK surface prevents osseointegration, resulting in poor cell attachment and greatly reduced bonding force with bone. Thus, a porous PEEK structure, and ideally a graded porous structure, is desired for PEEK-based implants. A novel PEEK implant fabrication method was recently developed based on immiscible polymer blending of PEEK and polyether sulfone (PES). A key step in the PEEK implant fabrication process is annealing, where the immiscible PEEK and PES undergo phase separation and coarsening, forming a co-continuous structure that, upon subsequent leaching of PES, creates an interconnected porous PEEK structure. The phase separation and coarsening process is critical to the proposed fabrication process, because it controls the pore size and gradient structure of the porous PEEK implant. In this study, we develop a two-dimensional (2D) process model based on the phase-field theory to understand the phase separation and growth process of PEEK/PES. Simulations were performed under various process conditions. The developed model provides qualitative understanding of the PEEK/PES annealing process and offers critical insights for optimizing high-strength porous PEEK fabrication.