Polyethylene Glycols in Aqueous & Non-Aqueous Solvents

Polyethylene glycol (PEG) is a non-linear polymer and consists of hydrophilic oxygen and hydrophobic ethylene units. The structure of aqueous solutions of PEG is an important subject from the point of view of polymer chemistry and surface and colloid science, since the hydration structure of this chain is closely related to the size and shape of micellies and the phase behaviour in surfactant and non-ionic polymer solutions.The apparent molar compressibility behaviour of solute describes the effect due to pressure on the modes of interaction. In case of electrolyte solutions, values are negative meaning loss of compressibility of water due to electrostriction. While for many non-electrolyte solutions positive or small negative values are observed. These have been explained in terms of dipole-dipole interactions, H-bonding and formation of soft structures in solution phase. The hydration number obtained is thus reliable and seems to depend upon the molecular weight, chain length. The PEG-400 (Mol. Wt. 404.98) is approximately similar to Bu4NBr, (Mol. Wt. 322.38) which exhibit hydration number of 26 in water.