Abstract:
The development of efficient multicomponent tandem polymerization (MCTP) has gained much interest
recently. Herein, fluorescent non-conjugated polyamide gels are synthesized via Biginelli synthesis in
one-pot under solvent free conditions using di-aldehyde and aliphatic di-amines in the presence of a
newly developed magnetic catalyst (IL2@Fe3O4 NPs). The formation of IL2@Fe3O4 NPs (in which magnetic
iron oxide NPs were coated with ionic liquid) was characterized via transmission electron microscopy
(TEM), powder X-ray diffraction (PXRD), vibrating sample magnetometer (VSM), and Brunauer–Emmett–
Teller (BET) studies. Polymerization in the presence of the new non-toxic magnetic catalyst proceeded
smoothly, even at room temperature, giving high molecular weight (Mw up to 83 384 g mol−1
) fluorescent
polyamide gels in excellent yields with the easy removal of the magnetic catalyst from the reaction
mixture. Thus, this approach showed great potential for being developed into a simple and efficient
polymerization approach for obtaining structurally diversified, Biginelli 3,4-dihydropyrimidin-2(1H)-ones
(DHPMs) in the polymer backbone. This overcomes the limitations of multicomponent polymerization,
such as stoichiometric balance, low molecular weight, complicated workup procedures, and the poor
solubility of polymeric products, and it also allows the easy removal of the catalyst. The structures of all
the prepared polyamide gels were established using 1
H-NMR, 13C-NMR, FT-IR spectroscopy and gel permeation chromatography (GPC) analysis. Moreover, thermogravimetric (TGA) analysis reveals that the
newly designed magnetic catalyst (IL@Fe3O4 NPs) possesses high thermal stability and can be reused, and
it remains unchanged, even up to the tenth cycle of the MCTP reaction.
