Abstract
We present a comprehensive approach to characterize the one-pot synthesis, macropore space morphology, and chromatographic performance of phenyl-modified macro–mesoporous silica monoliths.
Highlights
For the quantitative evaluation of the macropore space morphology, we reconstructed a PTMS–TMOS silica monolith at macropore resolution adapting confocal laser scanning microscopy (CLSM) followed by chord length distribution (CLD) analysis, as described previously for silica-based monoliths prepared from pure TMOS or from TMOS and methyltrimethoxysilane (MTMS).[22,32,33]
The overall carbon load of the PTMS–TMOS rod is higher than for the commercial phenylmodi ed silica particles (Section 2.1.), but since the phenylmodi cation refers to the bulk solid and the surface in the rod (Scheme 1) its surface coverage will be lower than for the particles, which are surface-modi ed in a traditional postfunctionalization procedure
TGA-MS, FT-IR and elemental analysis proved the presence of phenyl groups in the entire material, the majority of which remained intact despite the elevated temperature during heat-treatment applied to obtain intraskeleton mesopores
Summary
The more exible combination of the interskeleton macroporosity with the intraskeleton mesoporosity is a decided advantage of the silica-based monoliths over particulate packings regarding the use as stationary phase in separation science, adsorption technology and catalysis.[5,6,13,14,15,16] As a common feature, the macropore space of the silica monoliths enables advection-dominated transport by uid ow, whereas the mesopore space provides the surface area accessible by pore diffusion. For the quantitative evaluation of the macropore space morphology, we reconstructed a PTMS–TMOS silica monolith at macropore resolution adapting confocal laser scanning microscopy (CLSM) followed by chord length distribution (CLD) analysis, as described previously for silica-based monoliths prepared from pure TMOS or from TMOS and methyltrimethoxysilane (MTMS).[22,32,33] In CLD analysis the solid–void (silica–macropore) border is scanned with chords of variable length and the resulting distribution of the chord lengths indicates the relative frequency with which a certain silica–silica distance occurs in the macropore space of a monolith This is an abstract but accurate analytical approach to describe void space uctuations in a material, eliminating the need to de ne limits for individual pores or their geometric form. Results are compared to pure TMOS and MTMS–TMOS hybrid silica monoliths, which have been previously characterized by the same approach
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