PROTONATION STUDIES OF MULTIFUNCTIONAL POLYMERS WITH A POLY(AMIDO-AMINE) STRUCTURE

The protonation of some poly(amide-amines) has been studied in aqueous solution by both 13C n.m.r. and potentiometric methods. In particular 13C n.m.r. chemical shifts were plotted as a function of pH. In all cases the curves show points of inflexion at pH values which can be predicted from potentiometric pK values. 1,4-Diacyl piperazine groups are present in the main chain of the poly(amino-amine). We found that 50% cis and 50% trans isomers with respect to the carbonyls were present in aqueous solution; the cis trans ratio is independent of pH. Only 'apparent' constants were found in the previously described polymeric acids and bases; however, 'real' basicity constants could be determined for the poly(amido-amines) studied in the present work. Moreover, the protonated monomeric unit site could be determined exactly by both potentiometric and 13C n.m.r. methods. © 1978.