A Thermodynamic Study to Evidence the a,w-Dichloroalkane/Block Copolymer Mixed Aggregates Formation. Effect of the Copolymer Architecture

Abstract

The thermodynamics of 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 () and the volume () for the additive–copolymer mixed aggregates formation per additive molecule. for Cl2CH2 and Cl2(CH2)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. Cl2(CH2)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 in 10R5, whereas, it does influence in L35, enhancing the ability of the aggregate to extract the chlorinated compounds from the aqueous phase. The 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 -dichloroalkanes showed that Cl2CH2 and Cl2(CH2)2 prefer poly(ethylene oxide) (PEO), Cl2(CH2)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 solubilization into the polymeric aggregates