Polymer-Small Molecule Interactions

Abstract

The solubility and behaviour of polymers in solution is controlled by the balance of all the interactions between the solvent molecules and the polymer segments. In non aqueous systems, the solvent-solvent interaction is often weak, whilst in aqueous systems it is strong and can dominate the solution behaviour of polymers. When solid polymers are dissolved in relatively non-polar solvents, the main energy contribution to their dissolution comes from the entropy arising from the increased volume available to the solvent molecules¹. For polar polymers dissolving in polar solvents, there are important additional contributions from the interactions between dipoles or charges. Water can be regarded as an extreme example of a polar liquid having, in addition to these simple elctrical interactions, an important three dimensional structure, disruption of which can produce large entropy changes. When polar molecules or ions dissolve in water, there must be sufficient energy from the solvent-water interaction to overcome any decrease in entropy, arising from the change in ordering of the water molecules.