Tuning of the molecular packing structure of comb-shaped polymer-grafted silica by using surface-initiated ATRP to enhance the molecular-shape selectivity towards polycyclic aromatic hydrocarbons

Poly(octadecyl acrylate)-grafted silicas were prepared by surface-initiated atom transfer radical polymerization (ATRP). Initially, undecyl ester and allyl ester-based ATRP initiators were synthesized and then immobilized on silica. The surface-initiated ATRP of octadecyl acrylate was carried out from the initiator-grafted silicas using copper(I) bromide and N,N,N′,N′,N′′-pentamethyldiethylenetriamine as catalyst precursors to produce poly(octadecyl acrylate)-grafted silicas, Sil-C11-ODAn (obtained from undecyl ester) and Sil-C3-ODAn (originated from allyl ester), respectively. Both Sil-C11-ODAn and Sil-C3-ODAn were characterized by DRIFT, suspension-state 1H NMR, solid-state 13C CP/MAS NMR spectroscopies, thermogravimetric analysis (TGA), elemental analysis and differential scanning calorimetry (DSC) measurements. Suspension-state 1H NMR, solid-state 13C CP/MAS NMR and DSC analyses suggest that Sil-C11-ODAn demonstrated more ordered structure than Sil-C3-ODAn. In this paper, it is also described that for ordering of the polymer phase is accompanied by the selectivity increase for the separation of poly cyclic aromatic hydrocarbons (PAHs) in RP-HPLC.