Synthesis and characterization of novel aromatic poly(benzimidazole-amide)/Ag and Cu nanocomposites through transition metal complexation

A new thermally stable aromatic poly(benzimidazole-amide)s PBIAs was synthesized by low-temperature polycondensation of bis-benzimidazole diamines; 1,4-bis(5-amino-1H-benzimidazol-2-yl)benzene (3a) and 1,3-bis(5-amino-1H-benzimidazol-2-yl)benzene (3b) with two different diacid chlorides. Diamines 3a and 3b were prepared via direct condensation of 1,2-phenylene diamine and terephthalic or isophthalic acid in polyphosphoric acid in high yield. Chemical structures of synthesized monomers were confirmed by elemental analyses and spectroscopic methods. The structures of synthetized polymers were confirmed by FT-IR, ¹H-NMR, elemental and thermogravimetric analysis (TGA), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Thermal stability of the polymers was ascertained via 10 % weight loss temperatures in the range of 315–380 °C (inert atmosphere). Existence of benzimidazole moieties in polymer’s structure makes them suitable for easy coordination to Lewis acids or metallic ions, whereas the substitution of C–H or N–H protons allows for the synthesis of complex derivatives. As a result, a series of novel nanocomposites, via metal complexation of PBIA6a due to their great solubility with Ag⁺ or Cu²⁺ cations followed by reduction to metals by sodium borohydride (NaBH₄), was prepared. The resulting nanocomposites’ structures were confirmed by FT-IR, XRD, TGA, UV/vis, FE-SEM, TEM and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM–EDX). The FE-SEM, TEM and SEM–EDX results indicated that Cu and Ag particles were dispersed homogenously in nano scale in the polymer matrix.