Effects of Chain Molecules on the Temperature of the Maximum Density of Water

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Abstract
The shifts in the temperature of the maximum density of water produced by the addition of small amounts of oligomers of polyethylene glycol and polyethylenimine and other related compounds were determined by dilatometry. These effects were interpreted in terms of the change in the structure of water around the various solute molecules in connection with their chain length. It was found that, as the chain length increases, the extent of the modification of the water structure by the chain molecules decreases because of the hydrophobic contact between ethylene groups. The apparent specific expansibility of the solute in the neighbourhood of 4°C was also evaluated as a function of the concentration.