Abstract

The synthesis of polyfunctional aliphatic oligomeric polyesters (poly(ether-imido-esters; PEIEs) containing several amino acid residues is described, and their thermal properties and solubility behavior were studied. The new symmetrical monomeric dicarboxylic acids were synthesized using 4-nitrophthalonitrile as starting material, which reacted with bisphenol-A or bis(4-hydroxyphenyl)diphenylmethane. Then, the tetranitrile derivatives were hydrolyzed to the tetracarboxylic acids and dehydrated to the respective dianhydrides. Finally, these compounds reacted with the amino acids glycine or L-alanine to obtain the aliphatic dicarboxylic acid monomers. PEIEs were obtained by Higashi methodology from these monomers and bisphenol-A, characterized by elemental analysis, NMR and IR, and the results were in agreement with the structures. The materials were soluble at 25 °C in several aprotic polar organic solvents and some in CHCl3 and THF. In agreement with the viscosity and SEC results, PEIEs were oligomers with degree of polymerization of four and six, and Mw and Mn between 7370–9790 g/mol and 3680–4850 g/mol, respectively. The samples showed low Tg values (124–160 °C), associated with important structural flexibility promotes by dicarboxylic acid monomers. Despite this, this parameter depended of the aminoacidic residue nature in the sense that when the volume of it increased, the Tg also increased due to a decrease in the free rotation that negatively affects the segmental movements of the chains. This effect was also observed when the side groups of the diphenol moiety of the dicarboxylic acid monomers increase from methyl to phenyl. The recorded TDT10% values from the TGA analysis (334–457 °C) do not allow to consider these samples as thermoset materials. In this sense, it was possible to observe an average increase of 8–13 °C and 23–28 °C when the lateral group volume of the amino acid residues and of the diphenol moiety are increased, respectively.