Stability of styrene–maleamic acid interpolymers

Abstract

Abstract The response to heat and water of copoly(styrene–maleamic acid, ammonium salt), prepared by treatment with ammonia of the anhydride polymer in toluene suspension, is described. This polymer except for the ammonia bound by salt formation, is stable to heat within the range studied, i.e., to 100°C. The behavior of water solution is determined by the ammonia concentration. Above pH 9, the bound nitrogen remains as amide. If the pH is low, i.e., about 5, as occurs when a dried sample is dissolved in water, then rapid imidization occurs with concurrent hydrolysis. In the early stages of this conversion, imidization occurs mainly through loss of ammonia. This requires that two amide groups be adjacent. Classical imidization by loss of water also occurs, indicating that the normal‐amic acid structure is also present.