A precursor blend for preparing a thermoplastic polymer for a fiber-reinforced composite material includes a major amount of a stoichiometric mixture of a diepoxide, and an amine compound selected from the group consisting of monofunctional primary amine and difunctional secondary amine, and a minor amount of a modifier selected from the group consisting of difunctional primary amine, trifunctional primary amine, triepoxide, tetraepoxide, and combinations thereof.