Dual polyhedral oligomeric silsesquioxanes polymerization approach to mutually-mediated separation mechanisms of hybrid monolithic stationary and mobile phases towards small molecules

Hybrid monolithic stationary phase based HPLC is a typical example of practices in separation science. In this study, we developed a dual polyhedral oligomeric silsesquioxanes (POSS) polymerization approach to the preparation of a hybrid monolithic stationary phase of tri-porous structure and various surface chemistry. N-phenylaminopropyl-POSS (PA-POSS) and glycidyl-POSS (EP-POSS) were exemplified to demonstrate effective mutually-mediated separation mechanisms of the hybrid monolithic stationary phase and mobile phase towards diverse small molecules. PA-POSS and EP-POSS can be the monomer and/or crosslinker each other. They were polymerized via the epoxy-ring opening reaction to form the poly[(PA-POSS)-(EP-POSS)] (polyPOSS) monolithic stationary phase of 110.6/164.6 Å3 micropore (as a cube/ball), 10 nm mesopore and 0.95 μm macropore with the native siloxane cage and remaining phenyl/epoxy as well as chemically generated positive-chargeable tertiary phenylamine and hydrophilic hydroxyl groups. Such pore-structure and surface chemistry allow us to perform the effective separation of targeted small molecules, such as alkylbenzenes and alkylbenzene ketones, nucleic acid bases and amino acids, as well as phenols and phenolic acids, under reversed-phase, HILIC and mixed mode (polarity, size-exclusion and hydrogen-bonding) by just changing the molar ratio of POSS-precursors, and the composition and pH of a mobile phase as well. We believe that the approach developed herein can be extended to fabricate other kinds of hybrid monolithic stationary phases that are suitable for the separation of biomacromolecules and chiral molecules when choosing the existed POSS and/or designing new POSS with the substituted pendant groups of different physicochemical properties.