<p>A new tertiary aliphatic poly(amic acid), having linear and cyclic spacers, was fabricated through the catalyst-free process. The ring opening of ethylenediamine tetraacetic acid dianhydride by piperazine, a bifunctional cyclic secondary diamine, was conducted in a polar solvent in a nitrogen atmosphere. Piperazine was chosen to prevent the subsequent imidization of as-obtained poly(amic acid) and conserve the carboxyl and amide functional groups. The characterization was conducted using FTIR and NMR, and their morphology and elemental composition were investigated by field emission scanning electron microscopy and energy-dispersive X-ray. The white powder of as-synthesized poly(amic acid) showed an O/N ratio of 0.93 ± 0.03 and morphology of woven fiber. The white powder showed an average molecular weight (<i>M̅</i>_w) of ∼ 12,000 and a polydispersity index of 1.52 ± 0.05. Thermal degradation and phase transitions of new poly(amic acid) were studied using TGA/DTG and DSC. Then as-prepared poly(amic acid) was employed as a heterogeneous catalyst for Knovenagel condensation of various (hetero)aryl aldehydes with ethyl cyanoacetate, which is a less-active methylene acid compared with malononitrile. The reactions were carried out under green conditions, i.e., at room temperature using a ball mill under solvent-free conditions, and the pure Knoevenagel products were obtained in 88–96% yield after 20–60&#xa0;min of milling time.</p> Graphical abstract <p></p>