Synthesis and characterisation of aliphatic hyperbranched polyamidoamines and polyamides

Abstract

Dendrimers are perfectly branched macromolecules possessing large internal cavities and a known number and location of terminal groups. This unique architecture leads to many interesting properties and countless potential applications have been discussed. Their synthesis involves numerous repetitive steps, often requiring protection and deprotection chemistry and complex purification procedures. This limits their availability and leads to extremely high costs, a factor that has limited their use. Polyamidoamine (PAMAM) dendrimers, the first well-established series of dendrimers, were reported in the mid nineteen eighties. For many applications the synthetic difficulties associated with dendrimers are so great that many potential applications are prohibited. Hyperbranched polymers are produced by a simpler synthetic route, the step growth polymerisation of AB(_x) monomers in a one-pot procedure. They lack the architectural perfection of dendrimers but retain the large number of terminal groups and high degree of branching. Crucially, these polymers can be produced for a fraction of the cost of dendrimers. The synthesis of hyperbranched analogues to both the full and half generation PAMAM dendrimers from AB(_2) monomers is reported here. Attempts to extend this method to control the molecular weight, degree of branching and the terminal group functionality are discussed, as is the synthesis of a related series of polyamides. The characterisation of these materials and their physical properties are also described.