Piperazine-containing polyamide complexes with Co2+ ions and the related solvatochromic effect

A new and simple method was established to prepare polyamides with a chelating feature through Michael addition and polycondensation. A piperazine-diester monomer, that is, N,N´-bis(methyl propanoate) piperazine (BMPZ), was synthesized through a Michael addition of piperazine and methyl acrylate. Three polyamides containing piperazine rings (PIP-PAs) were synthesized via melt polycondensation from BMPZ and different diamines. PIP-PAs were modified by chelating Co2+, and several PIP-PA-Co2+ complexes were obtained. The structure of BMPZ and PIP-PAs was characterized by FT-IR and 1H NMR spectra. DSC and wide angle X-ray diffraction verified the crystallizable feature of PIP-PAs. They possessed Tm from 81 °C to 171 °C, tensile strength up to 31 MPa, and good toughness. Chelating PIP-PAs with Co2+ was accompanied by color change and the loss of crystallization. The effect of chelation on Tg, tensile strength, and Young's modulus was investigated. Polyamide complexes with good mechanical property and solvatochromic feature were synthesized successfully.