Influence of alkyl peptidoamines on the structure of functionalized mesoporous silica

The functionalization of mesoporous silica materials with alkyl peptidoamines by the cocondensation method was investigated. Alkylpeptidoamines were introduced via (aminopropyl)triethoxysilane (APTES). Samples were prepared by using a nonionic fluorinated surfactant CF3(CF2)(7)C2H4(OC2H4)(9)OH. Results obtained by SAXS and nitrogen adsorption-desorption analysis clearly showed that the channel arrangement of the recovered materials depends not only on the organosilane/(organosilane+tetramethyl orthosilicate) molar fraction but also on the nature of the functional groups. Indeed, materials functionalized with BOC-Phe-APTES or with small amounts of BOC-Glu(alphaOBn)-betaAla-APTES exhibit a hexagonal channel array. Higher BOC-Glu(alphaObetan)-betaAla-APTES loading leads to a wormhole-like mesostructure. Whatever the organosilane/(organosilane+tetramethyl orthosilicate) molar fraction, only disordered structures are recovered when functionalization is performed with Z-Asp(alphaOBn)-APTES. Moreover, the pore wall thickness is strongly affected by the structure of the organic groups. The efficiency of the functionalization was evidenced by FTIR and solid state Si-29 and C-13 MAS NMR spectroscopies. Results obtained from solid state Si-29 NMR also show that polymerization rates of organosilane and tretramethyl orthosilicate must be very close to each other.