Facile synthesis of micron-sized thiol-functional polysilsesquioxane microspheres through a one-step sol-gel method

Polysilsesquioxane (PSQ) is a promising organic-inorganic material, yet the existing studies about large micron-sized PSQ microspheres are relatively rare. In this work, a facile one-step sol-gel method in water/ethanol medium with methyltrimethoxysilane and (3-mercaptopropyl)trimethoxysilane as precursors, polyvinylpyrrolidone (PVP) as a dispersant, and NaOH as a catalyst, has been developed for synthesizing large micron-sized thiol-functionalized PSQ microspheres (TPMs). The composition of TPMs was characterized by FTIR and Raman spectroscopy, and the morphology of microspheres was characterized by optical microscopy and SEM. Results showed that the resultant microspheres had a high degree of sphericity and a homogeneous internal structure. The number-average diameter ( D mean ) and size distribution of microspheres can be controlled by the stirring rate, dosages of PVP and precursors, and concentrations of NaOH. Stirring was crucial for obtaining large microspheres. Without stirring, the microspheres were uniform, and the D mean was no more than 4.02 μm. With stirring, the obtained microspheres were comprised of large and small groups, and the D mean can be enlarged to 16.15 μm maximally. The formation mechanism was discussed based on monitoring the evolution of microsphere formation using optical microscopy and DLS. As an advanced material, the TPM is promising in the fields of adsorbent and catalyst support. Graphical Abstract Highlights Micron-sized TPMs are prepared by a one-step base-catalyzed method in the presence of PVP. Monodisperse small TPMs with a D mean of about 4 μm are synthesized without stirring by nucleation and growth. Large TPMs with a D mean larger than 10 μm are formed due to the coalescence of oligomer droplets with stirring.