We describe the syntheses and characterization of a series of periodic mesoporous organosilica (PMO)
materials containing various organic functional groups prepared using the direct synthesis method under
basic conditions. This synthetic method allows the production of mesoporous organosilicas that have
large surface areas and contain several different functional groups, such as a bridged amino, vinyl, ethyl,
glycidoxypropyl, and cyanopropyl units. Moreover, the type of organosilane used as a co-precursor has
a great influence on the final particle shape and modulates the overall properties of the resulting materials.
By changing the precursor type, along with its concentration, the particles can adopt various morphologies,
including rod-shaped and wormlike particles that have different degrees of bending. We propose a plausible
mechanism to explain the formation of these shapes. We have used X-ray diffraction (XRD) patterns,
nitrogen sorption properties, scanning electron microscopy (SEM), transmission electron microscopy
(TEM), thermogravimetric analysis (TGA), and 13C and 29S magic angle spinning (MAS) NMR
spectroscopy to characterize the structures and organic functionalities present in the resulting functionalized
PMO materials.
The catalytic cross-dehydrocoupling polymerization of 1,4-bis(dimethylsilyl)benzene with
water, ammonia, disilanol, aliphatic and aromatic diols, and dicarboxylic acids was successfully conducted
under mild conditions to afford silphenylene-containing polycarbosilazane, polycarbosiloxanes, poly(silyl
ether)s, and poly(silyl ester)s. This efficient novel route allowed accessing various silphenylene-containing
polymers with well-defined structures which were verified by NMR, IR, and SEC analyses. The influence
of the structures of the constitutional units between silphenylene groups on the transition temperatures,
crystallization behavior, thermal stability, solubility, and degradability of these polymers was also
systematically investigated.
Hydrolysis of trialkoxysilanes having various substituents gave cyclic tetrasiloxanetetraols with all-cis isomer as the major fraction in the presence of equimolar amounts of water and sodium hydroxide. All stereoisomers of phenyl derivative were produced by isomerization of the all-cis isomer in the presence of hydrochloric acid, and isolated and identified.
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