Unidirectional freezing as a tool for tailoring air permeability in macroporous poly(ethylene glycol)-based crosslinked networks

WALTER F. SCHROEDER; ROBERTO J. J. WILLIAMS; CRISTINA E. HOPPE; HERNÁN E. ROMEO

JOURNAL OF MATERIALS SCIENCE

SPRINGER

Lugar: Berlin; Año: 2017 vol. 52 p. 13669 - 13680

0022-2461

Unidirectional freezing followed by photopolymerization at sub-zero temperatures was usedto obtain highly air-permeable monoliths with ordered porous structures. Scaffolds wereobtained from aqueous solutions of a poly(ethylene glycol)dimethacrylate (PEGDMA)oligomer, a photosensitizer and a reducing agent. Solutions were vertically frozen in liquidnitrogen at a controlled rate to induce the oriented growth of ice crystals, and then cryophotopolymerized under blue-light irradiation. Ice crystals were finally removed undervacuum producing macroporous hydrophilic networks with aligned pores. Porosities rangedbetween 80 % and 95 %, depending on the initial concentration of PEGDMA. The influenceof processing variables on the final properties of the materials was addressed, concerningparticularly the effect of porosity and freezing directionality on air permeability. Compared toporous PEGDMA-based monoliths with non-aligned macropores, gas permeability was two tothree times higher for oriented scaffolds at the same porosity level, a fact explained by theeasier transport of gas molecules through the aligned structures. However, the role of poreorientation on gas permeability was shown to be less marked as porosity increased. Theresults demonstrate that the use of unidirectional freezing strongly increases the permeabilityof monolithic samples up to values usually required, for instance, in tissue engineeringapplications (higher than 2 D). These findings provide new perspectives on pore designprinciples towards future scaffolding of polymeric crosslinked matrices.