New composites of spherical bridged polysilsesquioxanes and aggregates of Pd nanoparticles with POSS via ionic interactions

Spherical bridged polysilsesquioxane (BPS) particles with sulfonic groups (BPS–SO₃ ⁻) were prepared by the subsequent reduction and oxidation of BPS with disulfide groups (BPS–S–S) after the hydrolysis and condensation reaction of silane monomers with disulfide groups under ammonia and alcoholic solutions. Spherical aggregates of Pd nanoparticles (Pd–polyhedral oligomeric silsesquioxanes, Pd–POSS) were produced by the mixing of POSS and palladium (II) acetate in methanol solution. The average size of BPS–SO₃ ⁻ and Pd–POSS was about 200–400 and 30–50 nm, respectively. New BPS–SO₃ ⁻/Pd–POSS composites with the shape of BPS–SO₃ ⁻ covered with Pd–POSS nanoparticles were fabricated by ionic interactions between negatively charged BPS–SO₃ ⁻ and positively charged Pd–POSS. Pd–POSS nanoparticles were more effectively attached to BPS–SO₃ ⁻ than BPS–S–S, which resulted from the difference of zeta potential between BPS–SO₃ ⁻ and BPS–S–S. That is, ionic interactions in BPS–SO₃ ⁻/Pd–POSS composites were stronger than those in BPS–S–S/Pd–POSS composites. As the storage time was increased, the precipitation of BPS–SO₃ ⁻/Pd–POSS composites in methanol solution resulted from the strong complex between BPS–SO₃ ⁻ and Pd–POSS unlike BPS–S–S/Pd–POSS composites. New particle composites were characterized by Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy.