Interaction of poly(oxyethylene) with water as a function of molar mass

Excess molar volumes and excess molar heat capacities of (polyethylene glycols + water) at temperatures betweenT=278 K andT=328 K

“…With an increase in temperature, hydrogen bonds are weakened, thus favouring the progressive dehydration of oxygen ethers and the release of the water structure. However, this effect is counterbalanced by an increase of hydrophobic interactions (5) leading to more compact conformations, and the growth of aggregates into microgels (2,7) is enhanced until the cloud point is reached. This results in less negative excess volumes and increasing positive excess heat capacities as the temperature increases.…”

“…In the case of the lower molar mass PEGs, the oxygen ether can be directly involved through hydrogen bonds in the water lattice, (14) and the hydrophobic interaction mainly controls the solution behaviour. (5) In general, it is assumed that a (water + PEG) complex is formed resulting in hydrogen bond formation between three water molecules and an ether oxygen, favouring an increase of the structure of the water surrounding the chains. (3,4) Thus, with an increase in the PEG concentration, aggregates coexisting with free molecular polymer chains are formed.…”

“…Despite their importance, it is surprising that relatively little attention has been paid to the determination of the thermodynamic properties of aqueous mixtures of PEGs over a wide range of molar masses and a wide range of temperatures. (5)(6)(7)(8)(9) Apart from the data of Malcolm and Rowlinson, (6) and those of Müller and Rasmussen (9) for the excess volumes of several PEGs, no data are available in the literature. To our knowledge, only few data by Andersson and Olofsson (8) on the heat capacities of aqueous polymer mixtures where concentration and temperature effects have been investigated exist.…”

“…The peculiar structures of PEGs in aqueous solutions have been investigated using different techniques (1)(2)(3)(4)(5) in order to ascertain their high solubility as compared to other polyethers (methylene, propylene, butylene oxides) for which a very low solubility is observed only with the shorter oligomers. Despite their importance, it is surprising that relatively little attention has been paid to the determination of the thermodynamic properties of aqueous mixtures of PEGs over a wide range of molar masses and a wide range of temperatures.…”

The effect of ΔG on the transport and oral absorption of macromolecules

“…Inulin has a more compact and cylindrical configuration relative to the extended chain configuration associated with PEG4000. 40,41 Size exclusion chromatography proved that despite the higher mw of Inulin, it has a molecular configuration that contributes to its retardation behind PEG4000. 42 In addition, some investigators suggested the presence of low mw polysaccharide impurities in commercially available Inulin.…”