. . . " done by recrystallization from an organic solvent, such as ethyl acetate, or a mixture of ethyl acetate and hexane. [0060] This procedure may be used to prepare a variety of 2,5-dialkoxyterephthalic acids. [0061] Preparation of the Polymer [0062] The polymers and copolymers of this invention have about at least 20 repeat units, which may independently be the same or different, represented by the" .