Interaction of polymers with solvents including water

6 Interaction of polymers with solvents including water 

As a consequence of their size, polymers interact with solvents in a more complex fashion 

Highly polar polymers like polyfvinyl chloride) and some cellulose derivatives require polar liquids as solvents, in which dipole interactions or hydrogen bonding between polymer and solvent molecules occur. However, solvation does not necessarily lead to solution because the liquid, if it is to act as a solvent, must dissolve the solvated polymer. This process may be very slow because of the high viscosity of the partially solvated system. 

The relative mobility of a drug diffusing in the swelling hydrogel is given by the swelling 

It has been seen in Chapter 7 that the use of macromolecules as dispersion stabilisers depends in part on the osmotic forces arising from the interaction of solvated polymer chains as neighbouring particles approach (see Fig. 7.7). It is thus important to know how factors such as temperature and additive affect this interaction. Flory has given the free energy of dilution (the opposite process to the concentration effect discussed in section 7.2) 

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