engleski

Temperature and electrolyte concentration influence on formation of polyelectrolyte multilayers and complexes in solution

The formation of polyelectrolyte multilayers of polyallylammonium cation (PAH) and polystyrenesulfonate anion (PSS) was investigated in aqueous solutions of NaClO4 at 25 °C and 40°C by means of quartz crystal microbalance with dissipation monitoring (QCM- D). The obtained results showed that there was no significant difference between total adsorbed mass of polyelectrolytes at 25 °C and 40 °C (8 layers deposited in 0.5 mol dm–3 NaClO4). However, change in electrolyte concentration from 0.1 mol dm–3 to 0.5 mol dm–3 led to the difference in the amount of positively charged polyelectrolyte incorporated into multilayers. At lower concentration of salt, the amount of adsorbed PAH was lower than PSS, but at higher concentration, the amount of adsorbed PAH became much larger than PSS. This is in accordance with DLS results for aggregation of positive colloid complexes which showed that there was no aggregation of complexes at 0.1 mol dm–3 and the same concentration of PAH as in QCM-D experiments. Spectrophotometric study of the supernatant in 1:1 reaction mixture of PAH and PSS was also performed at different temperatures and NaClO4 concentration. Results showed that equilibration in the system was very slow, but it was considerably affected by increasing temperature and ionic strength of solution. For instance, at 60 °C in 2 mol dm–3 NaClO4, equilibrium was reached within 24 hours. Also, when the ionic strength in solution was higher, there was more pronounced asymmetric incorporation of polyelectrolytes in the product of reaction in solution which is in accordance with asymmetric incorporation of polyelectrolytes into multilayers.

polyelectrolytes ; multilayers ; quartz crystal microbalance

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