This paper analyzes solvation and association in macromolecular solvents using mean-field theory applied to several lattice-gas models. The thermodynamic functions of solvation and the equilibrium constant for association is calculated in terms of the temperature, pressure, and solvent molecular size. Applications to ion association in polymer electrolytes are discussed and the advantages and flaws of the model are critically analyzed. Exact results for a simple one dimensional model are also obtained and discussed.