Soluting-In and Soluting-Out of Water-Soluble Polymers in Aqueous Carbohydrate Solutions Studied by Vapor Pressure Osmometry

Precise vapor pressure osmometry (VPO) measurements at 308.15 K have been performed for ternarysystems of carbohydrate in aqueous 0.2 w/w polymer solutions. The polymers are polyethylene glycol 400 (PEG400),polyethylene glycol 10000 (PEG10000) and polypropylene glycol 400 (PPG400), and the carbohydrates are xylose,xylitol, glucose, fructose, sucrose and raffinose. In order to study the soluting-out and soluting-in effects occurring inthe polymer-carbohydrate aqueous systems, deviations of vapor-liquid equilibria behavior of these systems from thesemi-ideal state have been evaluated. The VPO data obtained for PEG-carbohydrate aqueous systems, which arecompletely miscible, generally show positive deviations (soluting-in effect) from the semi-ideal behaviour that becomemore positive by increasing hydrophobic nature of PEG and carbohydrates. However, in the case of PPG +carbohydrates aqueous systems that can undergo phase separation, the VPO data in the monophasic and biphasicregions, respectively show negative (soluting-out effect) and positive deviations from the semi-ideal behaviour. In thesesystems, because of unfavorable PPG-carbohydrate interactions, the solutes exclude themselves from the vicinity ofeach other and therefore aqueous biphasic systems are entropically formed above a critical concentration.

کلیدواژه ها:

Vapor pressure osmometry ، Water-soluble polymer ، Carbohydrate ، Semi-ideal behavior ، Soluting effects