POLY(AMIDOAMINE) HYPERBRANCHED SYSTEMS - SYNTHESIS, STRUCTURE AND CHARACTERIZATION

Hyperbranched analogues of the Tomalia PAMAM dendrimer system have bee n prepared from a series of AB(2) aminoacrylate hydrochloride monomers using Michael addition chemistry, where A represents a Michael accept or and B-2 a primary aliphatic amine. This step-growth polymerization process has led to the synthesis of poly(amidoamine) hyperbranched mat erials, examples of which exhibit a branching factor close to one. Thi s degree of branching, calculated from quantitative N-15 NMR spectrosc opy data, is consistent with other spectroscopic characterization unde rtaken and the assignment of the N-15 NMR shifts observed correlates w ell with the available literature data. The use of MALDI-TOF mass spec trometry as a tool to evaluate the possibility of intramolecular cycli zation reactions between the focus and terminal groups is discussed al ong with the determination of molecular weights and molecular weight d istributions for these amidoamine hyperbranched polymers. The synthesi s of pseudo-dendrimers through 'one-pot' AB(2)/B-n copolymerizations, where control over both molecular weight and extent of branching throu gh the B-n unit is illustrated. A poly(amidoamine) hyperbranched AB(2) /B-6 copolymer is shown to display a viscosity/molecular weight profil e similar to that exhibited by dendrimers. The effect of varying the i nternal spacer unit length between the branch points A and B is discus sed, with reference to both the standard AB(2) polymerizations and the core terminated AB(2)/B-n copolymerizations. Preliminary physical cha racterisation (T-g, DSC and solution viscosity) of these novel materia ls is reported. (C) 1998 Elsevier Science Ltd. All rights reserved.