Entrapment of functionalized silica microspheres with photo-initiated acrylate-based polymers

The entrapment of silica-based microspheres, commonly used as stationary phases in chromatography, with an organic porous polymer based on poly(butyl acrylate-co-1,3-butanediol diacrylate) was explored. The spheres were immobilized by photopolymerization leading to entrapped beds within 75 μm i.d. fused silica capillaries, and were mechanically stable, resisting pressure drops of over 5600 psi (38.6 MPa) for only 1 cm of material. The morphology of the polymer formation around the spheres was investigated by SEM and corroborated with back pressure measurements, which indicated that the spheres were held together by encapsulating polymer. The entrapped material was extruded from the capillary in some cases to facilitate imaging. The entrapment conditions were explored, varying the polarity of the sphere surface, the solvent, and the monomers, revealing that polymer formation is based on partitioning of the monomers between the surface and solvent. The resulting polymer morphology is discussed with respect to the effects of confinement, supported by experiments with varying microsphere diameters. The columns described here have favourable properties for use in capillary chromatography and supported catalysis among other applications, and is suitable for lab-on-a-chip devices.

Graphical abstractFunctionalized silica microspheres are entrapped such that polymer forms only on the surface of the spheres, where the resulting material is robust enough to be extruded from a capillary.Figure optionsDownload full-size imageDownload as PowerPoint slide