Preparation of epoxy-functionalized hierarchically porous hybrid monoliths via free radical polymerization and application in HILIC enrichment of glycopeptides.

Owing to their multiscale pore size regimes and unique properties, the materials with hierarchically porous structures have become an important family of functional materials in recent years. They have been applied from energy conversion and storage, catalysis, separation to drug delivery, etc. The synthesis of them is difficult by the need to employ multiple templates and take complicated steps. Herein, we successfully prepared epoxy-functionalized hierarchically porous hybrid monoliths (HPHMs) with micro/meso/macro-structures in an easy way. Firstly, a bulk monolithic material was formed via free radical polymerization between polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) and allyl glycidyl ether (AGE) in the presence of polycaprolactone (PCL). Then PCL was degraded with hydrochloric acid solution, and the epoxy-functionalized HPHM was obtained. This approach was very simple and suitable for large-scale preparation. Hybrid monoliths with different specific surface area (from 5.4 to 636.7 m2/g) were prepared by adjusting the mole ratio of vinylPOSS to AGE and the content of PCL. The results of several characterization methods, including nitrogen adsorption/desorption measurements, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), showed that these materials contained not only micropores and mesopores but also macropores. The materials were further modified with penicillamine to be used as hydrophilic interaction chromatography (HILIC) adsorbents for enriching N-glycopeptides in IgG and serum protein tryptic digests. Up to 23 N-glycopeptides were identified from IgG digest, and 385 N-glycopeptides and 283 N-glycosylation sites were identified from human serum digest.