A thermodynamic study to evidence the alpha,omega-dichloroalkane/ block copolymer mixed aggregates formation: effect of the copolymer architecture.
The thermodynamics of alpha,omega-dichloroalkanes in aqueous solutions of (ethylene oxide)(11)(propylene oxide)(16)(ethylene oxide)(11) (L35) and (propylene oxide)(8)(ethylene oxide)(23)(propylene oxide)(8) (10R5) was determined at 298 and 305 K. Modeling the experimental data allowed to calculate the standard free energy (DeltaG(D)(o)/w) and the volume (DeltaV(D)/w) for the additive-copolymer mixed aggregates formation per additive molecule. DeltaG(D)(o)/w for Cl(2)CH(2) and Cl(2)(CH(2))(2) evidenced that the process is controlled by the forces exercising between the chlorine atoms and the OH groups of the copolymer micelles protruded into the aqueous phase. Cl(2)(CH(2))(3) experiences both the hydrophilic and hydrophobic domains into the aggregates. The hydrophobic interactions are more significant in 10R5 whereas the hydrophilic ones are more significant in L35. Temperature increase does not influence DeltaG(D)(o)/w in 10R5, whereas, it does influence DeltaG(D)(o)/w in L35, enhancing the ability of the aggregate to extract the chlorinated compounds from the aqueous phase. The DeltaV(D)/w values are consistent with the free energy results. These insights agree with those predicted by the Flory liquid lattice theory. The calculations extended to several alpha,omega-dichloroalkanes showed that Cl(2)CH(2) and Cl(2)(CH(2))(2) prefer poly(ethylene oxide) (PEO), Cl(2)(CH(2))(3) exhibits the same affinity for both PEO and poly(propylene oxide) (PPO), whereas the more hydrophobic additives show a preference for PPO. The copolymer architecture plays a relevant role in the alpha,omega-dichloroalkane solubilization into the polymeric aggregates.
De Lisi
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Dipartimento di Chimica Fisica F. Accascina, Università degli Studi di Palermo, Viale delle Scienze, Parco D'Orleans II, 90128 Palermo, Italy.
Lazzara
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Milioto
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Muratore
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