NMR-STUDIES, MOLECULAR CHARACTERIZATION, AND DEGRADATION BEHAVIOR OF POLY(AMIDO AMINE)S .1. POLY(AMIDO AMINE) DERIVING FROM THE POLYADDITION OF 2-METHYLPIPERAZINE TO 1,4-BIS(ACRYLOYL)PIPERAZINE

Poly(amido amine)s (PAAs) are a family of water soluble polymers endow ed with properties which find useful applications in the medical field . In order to perform degradation studies on PAAs by using GPC in aque ous media, a calibration curve was derived by following a purposely de veloped procedure. A set of PAA samples having different molecular wei ghts were synthesized, by means of stepwise polyaddition reactions, ca rried out with nonstoichiometric ratios of the monomers. A careful cha racterization of the samples was performed by means of H-1, C-13, and bidimensional homo- and heterocorrelated NMR spectrometry. Particular attention was devoted to the quantitative determination of end functio nalities, which enabled us to calculate the number-average molecular w eight of PAA samples. The GPC results, obtained in buffered aqueous so lution, were combined with NMR data on number-average molecular weight , and by means of a nonlinear least squares fitting procedure, followi ng iterative routines, a linear calibration curve of log M versus rete ntion times was obtained. Weight averages and the polydispersity index for the PAA samples were then determined. Finally, from viscometric m easurements,the Mark-Houwink constants were also determined using numb er-average molecular weights.