Direct Immobilization of Living Poly(2-ethyl-2-oxazoline) Chains onto Mesoporous Silica: A Simplified Grafting-To Strategy for Hybrid Organic-Inorganic Materials.

The development of straightforward and efficient strategies for the preparation of polymer-functionalized mesoporous silica remains an important challenge in the design of advanced hybrid materials. Herein, we report a novel and simplified approach to the covalent functionalization of mesoporous silica particles (MSP) with poly(2-ethyl-2-oxazoline) (PEtOx), based on the direct termination of living cationic polymer chains by amino groups immobilized on the silica surface. In contrast to conventional grafting-to methods, the proposed strategy eliminates the need for polymer end-group functionalization while avoiding the synthetic complexity associated with surface-initiated polymerization. Well-defined PEtOx chains with number-average molar masses of 5000 and 7500 g mol-1 were synthesized by cationic ring-opening polymerization (CROP) and subsequently grafted onto amino-functionalized MSP. Successful covalent immobilization of the polymer was confirmed by Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), contact angle measurements, and nitrogen adsorption-desorption studies. The modification preserved the ordered mesoporous architecture while increasing particle hydrophilicity and decreasing the specific surface area and pore volume due to polymer incorporation. Shorter polymer chains exhibited higher grafting efficiency than higher-molar-mass analog, indicating that steric hindrance is an important factor influencing the grafting process. The presented methodology provides a versatile and experimentally accessible platform for the preparation of well-defined poly(2-oxazoline)-functionalized mesoporous silica with tunable physicochemical properties. Owing to the combination of a porous inorganic framework and a polymer shell, the obtained hybrid materials represent promising candidates for drug delivery, adsorption technologies, and other advanced biomedical and environmental applications.