Thermally stable salts of polyvinylphthalic acid^†

The heretofore unreported monomer 4-vinylphthalic acid has been synthesized and characterized. Polymerization in aqueous solution employing a peroxydisulfate–hyposulfite redox catalyst system yielded glasslike polyvinylphthalic acid. Molecular weights of polyvinylphthalic acid appear to be in the range of 10⁴–10⁵. Alkaline earth polyphthalates show thermal stability to temperatures of 560°C. for periods of approximately 1 hr. Phthalocyanine crosslinks can be formed between chains of polyvinylphthalic acid, but such polymers do not show remarkable thermal stability.