New poly(amidoamine)s containing disulfide linkages in their main chain

Novel poly(amidoamine)s (PAAs) containing disulfide linkages regularly arranged along their backbones were synthesized by the stepwise polyaddition of 2-methylpiperazine to N,N'-bis(acryloyl)cystamine (BACy1) or N,N'-bis(acryloyl)-(L)cystine (BACy2). Both bisacrylamides had, in turn, been obtained by the reaction of acryloyl chloride with the corresponding amines. All the products were characterized with H-1 and C-13 NMR spectroscopy, and the average molecular weights of the polymers were determined by size exclusion chromatography. Both PAAs showed different solubility properties. In particular, PAA-Cy1, derived from BACy1, was sparingly soluble in water, whereas PAA-Cy2, derived from BACy2, was very soluble in aqueous media. The polymerization rates were investigated with 1H NMR spectroscopy. In both cases, the experimental data were consistent with pseudo-second-order kinetics. The calcu lated kinetic constants were 5.96 X 10(-3) and 5.90 X 10(-2) min(-1) L mol(-1) for the polyaddition of BACy1 and BACy2, respectively. The observed hydrolytic degradation rate of PAA-Cy2 in a pH 7.4 tris(hydroxymethyl)aminomethane (TRIS) buffer was comparable to that of conventional amphoteric PAAs, that is, PAAs containing carboxyl groups in their repeating unit. Degradation experiments carried out in the presence of 2-mercaptoethanol with both PAAs demonstrated that the disulfide groups contained in its repeating units were susceptible to reductive cleavage in the presence of thiols. (c) 2005 Wiley Periodicals, Inc.