title: Postsynthesis vapor-phase functionalization of MCM-48 with hexamethyldisilazane and 3-aminopropyldimethylethoxylsilane for bioseparation applications.
abstract: MCM-48 was surface modified via vapor-phase reactions with hexamethyldisilazane (CH(3)-MCM-48) and 3-aminopropyldimethylethoxysilane (NH(2)-MCM-48). (29)Si NMR confirmed that the resulting materials contained covalently attached trimethylsilane and 3-aminopropyldimethylsilane moieties, both important functionalities for bioseparation applications. The surface coverage was approximately 1.8 and 0.9 groups per nm(2), respectively. The X-ray diffraction patterns and the narrow pore size distributions obtained from the gas sorption isotherms showed that the modified materials retained the characteristic pore structure of the underlying MCM-48 material. CH(3)-MCM-48 exhibited significantly improved hydrolytic stability over the unmodified MCM-48 under the aqueous conditions tested, whereas NH(2)-MCM-48 appeared to be less stable than the unmodified MCM-48. The decrease in stability is most likely due to the nature of the attachment of the 3-aminopropyldimethylsilane moiety, where the conversion of surface silanol groups is limited by H bonding with the amino end, leading to a 50% lower surface concentration and resulting in an increased likelihood of nucleophilic attack on the silica surface, enhancing the rate of hydrolysis. Hexamethyldisilazane thus appears to be a superior functional group for modifying the MCM-48 surface.
authors.affiliation: Department of Chemical and Biomolecular Engineering and School of Chemistry, The University of Melbourne, Victoria 3010, Australia. andreajo@unimelb.edu.au
authors.forename: Antje
authors.initials: A
authors.lastname: Daehler
authors.forename: Sasha
authors.initials: S
authors.lastname: Boskovic
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Gee
authors.forename: Frances
authors.initials: F
authors.lastname: Separovic
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Stevens
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: O'Connor
mesh_terms: D007202:Indicators and Reagents; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009584:Nitrogen; D017646:Organosilicon Compounds / Q000138:chemical synthesis* / Q000737:chemistry* / Q000302:isolation & purification; D011312:Pressure; D017640:Silicates / Q000138:chemical synthesis / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D007202:Indicators and Reagents; D017646:Organosilicon Compounds; D017640:Silicates; C024548:hexamethylsilazane; D009584:Nitrogen