Add time:08/27/2019         Source:sciencedirect.com

Secondary amine based organic/inorganic hybrid periodic mesoporous organosilica (PMO) materials were synthesised from a bridged silsesquioxane precursor, N,N'-bis[3-(triethoxysilyl)propyl] ethylenediamine (TESEN) and tetramethyl orthosilicate (TMOS) with various amounts of TESEN and TMOS. Cetyltrimethylammonium bromide (CTABr) was used as the structure directing agent under basic conditions. The pore opening of the material was modified with N-[3-(trimethoxysilyl)propyl]aniline (TMSPA) to impart a nanovalve property under acidic conditions when co-operating with the β-cyclodextrin (β-CD) molecule. The physico-chemical properties of N,N’-bis-(propyl)ethylenediamine-bridged PMO with 15% (w/w) organo-functionality (DA-PMO-15) and the corresponding nanovalve system (GA-PMO-15) were determined by a range of spectroscopic analyses. X-ray diffraction and transmission electron microscopy showed that the DA-PMO-15 and GA-PMO-15 materials possess mesocopically ordered, hexagonal symmetry and well-defined morphologies. 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectral analysis revealed the silicon environment of the final material. N2 sorption experiments showed the material has large surface area (591 m2 g−1), acceptable pore diameter (3.0 nm) and affordable pore volume (0.38 m3 g−1) to accommodate the guest molecules inside the pore channels. Organic functionalization was determined successfully by Fourier transform infrared and 13C cross-polarization magic angle spinning (CP-MAS) NMR spectroscopy. Acidic drugs, such as 5-fluorouracil and ibuprofen were chosen as the cargo and the release rate from the GA-PMO-15 nanovalve at pH 4 was delayed significantly due to the gate keepers and the interaction of drug molecules with the internally functionalised N,N’-bis-(propyl)ethylenediamine molecule.

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