Aliphatic‐aromatic polyamide‐imides from diisocyanates, 2. Study of the influence of the reaction conditions on polymer structure

Abstract

AbstractThe polycondensation of 4,4′‐methylenediphenylisocyanate and 6‐(4‐carboxyphthalimido)‐hexanoic acid was studied under different conditions in order to establish the influence of factors such as temperature, catalyst, stoichiometric disbalance, and addition order of reactants on the molecular weight and the chemical composition of the final polyamide‐imide. All these factors proved to influence the extent of possible side reactions that lead to undersirable functions, the main ones being urea functions that locate within the polymer backbone. Other side‐reactions proposed to explain the formation of acylureas or biurets did not take place in appreciable extent since these functions could not be detected by NMR spectroscopy. Therefore, particular emphasis was made to prevent the formation of urea by changing the polycondensation conditions. A first attempt to clarify the regularity degree of the polymers (amounts of head to tail and head to head addition) by 1H NMR spectroscopy was also made.