Open pore, elastomeric scaffolds through frustrated particle collapse

This article describes a procedure for making open cell porous elastomeric polymer composites with pore volumes from 40 to 68 vol%, particle loadings up to 49 vol%, and high exposed particle surface area to provide opportunities for multifunctionality. The method exploits particle packing limitations to provide the porous structure during solvent extraction from a melt extrudable solvent-loaded polymer gel composite. During the solvent extraction process, the composite contracts, concentrating the particles, which reduces the interparticle spacing until adjacent particles are nearly in contact. Further solvent removal after particle concentration results in polymer fibrillation and void formation. The final porosity of the composites is dependent on the particle packing efficiency with estimated pore volumes ranging from 39 to 43 vol% for spherical particles to 68 vol% for higher aspect ratio particles. In addition, the particles can be dissolved from the scaffold to leave the unfilled porous elastomer, or partially dissolved to generate a core–shell structure with an outer continuous porosity layer void of particulate surrounding a particle laden porous core. While solvent removal from the gel composite is required, the method does not require the use of a blowing agent, phase separation, or a sacrificial particulate porogen to generate an open porous composite. In addition, the solvent minimizes the viscosity rise associated with high particulate loadings to maintain the ability to melt process the material. It is anticipated that this method of generating open pore composites with available particle surface area will provide opportunities for novel catalyst supports, tissue engineering scaffolds, mass transport applications, and mechanically tailorable materials.