Dependence of adsorption from mixtures of polymers with different thermodynamic flexibility on adsorbent amount

Abstract

The adsorption from the solutions of polymer mixtures with thermodynamic flexibility: cis-1,4-polybutadiene rubber (PB) possessing flexible chain ( σ = 1.7) and cellulose triacetate (CTA) with stiff chain ( σ = 6.0) has been studied at different amounts of adsorbent in the system. Adsorption value Γ (mg/m 2), energy of the adsorption interaction Q (kJ/mol) and the extent of surface coverage θ have been estimated by IR spectroscopy technique. Analysis of the data obtained demonstrates different patterns for the dependence of adsorption characteristics of the polymers with varying flexibility of the molecular chain on adsorbent/solution ratio. The isotherms of adsorption from the binary solutions at three A/V ratios are explained by different adsorption capacity of high- and low-molecular fractions depending on both the polarity and the flexibility of the chains in polymers of different chemical nature. For the first time, we have demonstrated the inversion for the dependency of the character of adsorption and the energy of adsorption interaction on A/V ratio when switching from binary to ternary solutions. In particular, at the least of the studied A/V ratio the total energy of the adsorption interaction is the mean of the values of the energies of the adsorption interaction for PB and CTA in binary solutions. The increasing amount of adsorbent results in the increase of the total energy of the adsorption interaction from the mixture as compared with that for the binary solutions.