Soluting Effects of Various Additives on the Clouding Behavior of Poly(propylene glycol) 1000 in Aqueous Media

Adequate knowledge about the soluting effect of various additives on the phase behavior of thermoresponsive materials in aqueous solutions could provide valuable information for the proper design of their applications. This work explored the aqueous phase behavior of poly(propylene glycol) 1000 (PPG1000) as a thermoresponsive polymer, in the presence of various additives including salts (NaCl, Na2CO3, Na2SO4, Na(3)Cit and K(3)Cit), 1-alkyl-3-methylimidazolium halide ionic liquids ([C(2)mim] [Br], [C(4)mim] [Br], [C(8)mim] [Br], and [C(8)mim] [Cl]), and surfactants (sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB)). From the gathered results, the cloud point temperature values of PPG1000 aqueous solutions follow the order of SDS > DTAB > [C(8)mim] [Br] > [C(8)mim][Cl] > [C(4)mim] [Br] > [C-2 mim] [Br] > pure water > NaCl > Na2SO4 > Na2CO3 > K(3)Cit > Na(3)Cit. It can be seen that the studied surfactants and ionic liquids increase the water solubility of PPG1000 and induce the soluting-in effect on the PPG1000 aqueous solutions. However, the studied salts facilitate the clouding process of PPG1000 aqueous solutions and cause the soluting-out effect. The experimental visual cloud point results were satisfactorily correlated with a Setschenow-type equation, and soluting coefficients were determined for the investigated additives in the PPG1000 aqueous solutions.