Infrared study of the interaction of charged silica particles with TiO2 particles containing adsorbed cationic and anionic polyelectrolytes

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the adsorption of charged silica particles onto TiO2 particles coated with anionic sodium polyacrylate (NaPA) or cationic poly(diallyldimethylammonium) chloride (PDADMAC). To the best of our knowledge, this is the first time that IR spectroscopy has been used to study the interaction of a polymer layer on one particle with a second different particle. The results show that, once adsorbed on the TiO2 particle, the PDADMAC or the NaPA does not transfer to the silica particles. In the case of NaPA coated TiO2, positively charged silica particles deposit on the TiO2 and this is accompanied by a change in the relative intensities of the bands due to COOH and COO- groups. From this change in band intensity, it is calculated that only similar to 6% of the COO- groups located in the loops and tails bind to the silica particle. This shows that the polymer bridges the two particles through an electrostatic interaction with the outer COO- groups. Similarly, in the case of the TiO2 particles coated with PDADMAC, negatively charged silica deposits on the TiO2 and this is accompanied by an increase in intensity of the symmetric bending mode of the N+(CH3)(3) group. This change in band intensity arises from the binding of these cationic sites of the polymer to the negative surface sites on the silica.