Adsorption/Immobilization of Poly(Methyloctylsiloxane) on Silanized Silicas

Abstract

This work explores the influence of surface polarity on the process of adsorption of poly(methyloctylsiloxane) (PMOS) in silica pores. For this study, the polarity of the silica surface was modified, making it hydrophobic through silanization with chlorotrimethylsilane. Three silicas, with different characteristics, were modified and PMOS was deposited on each at several loadings. To determine the PMOS immobilized in each phase, non‐immobilized PMOS was extracted with hexane. Physical characterization was by nitrogen adsorption and elemental analysis, before and after extraction. Columns prepared with extracted material and with stationary phases prepared with PMOS on unmodified silicas, were evaluated with a mixed polarity test mixture. The results show that PMOS is not readily stabilized on the surface of silanized silica, indicating that silanols are necessary for the adsorption and fixation of polysiloxanes on silica.

Keywords:

• Stationary phases
• Poly(methyloctylsiloxane)
• Pre‐silanized silicas
• HPLC

Acknowledgments

The authors acknowledge financial support and fellowships from the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). They also thank Dr. Stefan Bachmann and Prof. Klaus Albert from Universität Tüebingen for the ²⁹Si NMR measurements.