Functionalization of porous siliceous materials, Part 2: Surface characterization by inverse gas chromatography

Bauer, Frank; Meyer, Ralf; Czihal, Saskia; Bertmer, Marko; Decker, Ulrich; Naumov, Sergej; Uhlig, Hans; Steinhart, Martin; Enke, Dirk

doi:10.1016/j.chroma.2019.06.031

Cited by 24 publications

(22 citation statements)

References 75 publications

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“…Both temperature dependent values can be received from the slope and the intercept of a linear plot of ΔG sp ads /AN against DN/AN, as illustrated in Fig. S5 (ESM) [62,63]. It should be noted that acid-base parameters for solid surfaces derived by IGC measurements depend on the employed approach and the DN and AN reference values [57,59].…”

Section: Inverse Gas Chromatography (Igc)mentioning

confidence: 99%

“…Bauer et al [63] demonstrated a significant change in K A /K D value for porous glass upon MPTMS functionalization (leading to the SH modification), where a strong basic character of the surface was observed. With respect to our synthesis, it is not possible to analyze the materials with their non-oxidized (SH) modification, because the polymer that is still in the pores prevents unbiased interaction of probe molecules with the surface.…”

Section: Inverse Gas Chromatography (Igc)mentioning

confidence: 99%

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In situ synthesis and characterization of sulfonic acid functionalized hierarchical silica monoliths

Enke

Meyer

Wenzel

et al. 2020

J Sol-Gel Sci Technol

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Surface functionalization of porous materials with sulfonic acid (SO3H) groups is of particular interest in applications involving ion exchange, acidic catalysis and proton conduction. Macro-mesoporous silica monoliths are ideal support structures for these applications, as they combine advection-dominated mass transport in the macropores with short diffusion lengths and a large surface area (available for functionalization) in their mesoporous skeleton. Here, we report on SO3H functionalized sol–gel silica monoliths with bimodal pore systems exhibiting macro- and mesoporosity, prepared according to a simple, efficient in situ synthesis protocol. Based on the co-condensation approach, thiol groups were introduced homogeneously into the pore structure, followed by their oxidation to SO3H groups and the simultaneous removal of the template. The macropore size, specific surface area, and coverage with SO3H groups are easily adjusted in this synthesis route. Importantly, the hybrid monoliths have a substantially narrower mesopore size distribution (relative standard deviation ~25%) than conventional sol–gel materials (>40%) and can be engineered crack-free in a robust column design (suitable for high-pressure flow-through operation) with mean mesopore size down to ~7 nm. They are characterized by IR spectroscopy, thermogravimetry, and elemental analysis as well as 13C and 29Si solid state NMR to corroborate the simple, efficient combination of sol–gel-based material synthesis, surface functionalization, and template removal (i.e., polymer extraction). Complementary, inverse gas chromatography is presented as a new approach to characterize the incorporated SO3H groups via surface energy analysis and particularly resolve changes in the Lewis acid–base characteristics engendered by that functionalization.

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Section: Inverse Gas Chromatography (Igc)mentioning

confidence: 99%

Section: Inverse Gas Chromatography (Igc)mentioning

confidence: 99%

In situ synthesis and characterization of sulfonic acid functionalized hierarchical silica monoliths

Enke

Meyer

Wenzel

et al. 2020

J Sol-Gel Sci Technol

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“…23 Moreover, the deposition of adsorbed polymer that is formed during the postsynthetic treatment is contemplated. 9 Covalently condensed structures that form inside pores 8 or a combination of the aforementioned grafting modes were postulated as well. 24 Furthermore, the literature reports that the transformation of thiol groups remains incomplete and that the unoxidized sulfur species depress the catalytic performance.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic insight into post-synthetic surface modification of porous glass beads as a silica model system

Wenzel

Eckert

Müller

et al. 2022

Phys. Chem. Chem. Phys.

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“…Porous glasses have been used in various application fields such as in catalysis, ion exchange, adsorption, and sensor technology [17][18][19]. Their chemical durability and surface, mainly determined by silanol groups that can be functionalized by a wide variety of organosilanes as coupling agents, are particularly interesting for potential applications in drug delivery [20]. Furthermore, porous glasses are characterized by narrow pore size distributions, with tunable pore diameters in the range of 1 to 1000 nm for specific applications as well as adjustable pore volumes.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, porous glasses are characterized by narrow pore size distributions, with tunable pore diameters in the range of 1 to 1000 nm for specific applications as well as adjustable pore volumes. These glasses can be prepared in various monolithic shapes like beads, flat membranes, fibers, and tubes [17][18][19][20]. As a result, porous glasses are suitable as model systems for fundamental studies on the diffusion of drugs in porous materials and their sustained release kinetics.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Drug Release from Mesoporous SiO2-Based Membranes with Variable Pore Structure and Geometry

et al. 2022

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Transdermal drug delivery systems (TDDSs) play important roles in therapy due to distinct advantages over other forms and types of drug application. While common TDDS patches mainly consist of polymeric matrices so far, inorganic carriers show numerous advantages such as high mechanical stability, possible re-use and re-loading of drugs, and a broad chemical compatibility with therapeutically relevant compounds and chemical enhancers. Mesoporous glasses can be prepared in different monolithic shapes, and offer a particularly wide range of possible pore volumes, pore diameters, and specific surface areas. Further, they show high loading capacities and favorable physical, technical, and biological properties. Here, we explored for the first time monolithic SiO2-based carriers as sustained release systems of therapeutic drugs. In an ideally stirred vessel as model system, we systematically analyzed the influence of pore diameter, pore volume, and the dimensions of glass monoliths on the loading and sustained release of different drugs, including anastrozole, xylazine, imiquimod, levetiracetam, and flunixin. Through multilinear regression, we calculated the influence of different parameters on drug loading and diffusion coefficients. The systematic variation of the mesoporous glass properties revealed pore volumes and drug loading concentrations, but not pore diameter or pore surface area as important parameters of drug loading and release kinetics. Other relevant effectors include the occurrence of lateral diffusion within the carrier and drug-specific properties such as adsorption. The structure–property relationships derived from our data will allow further fine-tuning of the systems according to their desired properties as TDDS, thus guiding towards optimal systems for their use in transdermal drug applications.

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Functionalization of porous siliceous materials, Part 2: Surface characterization by inverse gas chromatography

Cited by 24 publications

References 75 publications

In situ synthesis and characterization of sulfonic acid functionalized hierarchical silica monoliths

In situ synthesis and characterization of sulfonic acid functionalized hierarchical silica monoliths

Spectroscopic insight into post-synthetic surface modification of porous glass beads as a silica model system

Characterization of Drug Release from Mesoporous SiO2-Based Membranes with Variable Pore Structure and Geometry

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