Semi-Crystalline Hydrophobic Polyamidoamines: A New Family of Technological Materials?

The hitherto known polyamidoamines (PAAs) are not suitable as structural materials because they are usually water-soluble or swellable in water. This paper deals with the synthesis and characterization of semi-crystalline hydrophobic PAAs (H-PAAs) by combining different bis-sec-amines with bis-acrylamides obtained from C6–C12 bis-prim-amines. H-PAAs were initially obtained in a solution of benzyl alcohol, a solvent suitable for both monomers and polymers. Their number average molecular weights, M¯n, which were determined with 1H-NMR by evaluating the percentage of their terminal units, varied from 6000 to >10,000. The solubility, thermal properties, ignitability and water resistance of H-PAAs were determined. They were soluble in organic solvents, semi-crystalline and thermally stable. The most promising ones were also prepared using a bulk process, which has never been previously reported for PAA synthesis. In the form of films, these H-PAAs were apparently unaffected by water. The films underwent tensile and wettability tests. They showed similar Young moduli (260–263 MPa), whereas the maximum stress and the stress at break depended on the number of methylene groups of the starting bis-acrylamides. Their wettability was somewhat higher than that of common Nylons. Interestingly, none of the H-PAAs considered, either as films or powders, ignited after prolonged exposure to a methane flame.