Synthesis and modification of water-soluble hyperbranched poly(amidoamine)s

Abstract

The multi-step syntheses of two water-soluble AB(_2) monomers, N-acryloyl-1,2- diaminoethane hydrochloride and N-acryloyl-1,2-daminoethane, are reported. The melt polymerisation at 210 ºC for 4 hours of N-acryloyl-1,2-diaminoethane hydrochloride gave, by Michael additions of the terminal ammonium salts (B(_2) groups) of a monomer molecule or growing oligomer with the unreacted vinyl double bond (A group) of another monomer molecule or growing oligomer, hyperbranched macromolecules. High degrees of conversion, determined using (^1)H NMR spectroscopy, were obtained and a degree of branching, determined using (^15)N NMR spectroscopy, was found to be equal or close to 1. However, this method proved difficult to reproduce and the alternative aqueous solution polymerisation at 100 ºC for 10 days of this monomer was investigated. The use of ampoules closed with Teflon taps as reactors lead to polymers displaying random signs of free radical polymerisation and high degrees of conversion due to such side-reaction, whereas, the alternative use of sealed Carius tubes lead to lower DP materials displaying no significant signs of free radical side-reactions. The kinetic study of this polymerisation allowed the determination of the rate constant associated with the oligomer growth and the MALDI analysis of these polymers revealed an evolution with time of the oligomer molecular weight distribution with time in agreement with the theoretical prediction. This last study also revealed that at least 70% of the molecules were not cyclised. On the other hand, the aqueous solution polymerisation of the corresponding free base monomer, N-acryloyl-1,2- diaminoethane, at 100 ºC for 90 minutes lead to hyperbranched macromolecules with high DP values. The kinetic study did not allow a precise determination of the rate constant associated with the oligomer growth due to the high reactivity of the free terminal amino groups. The MALDI analysis of these polymer samples showed that the evolution with time of the oligomer molecular weight distribution did not follow the theoretical prediction and that these macromolecules were cyclised.