Investigation of morphological aspects and thermal properties of ZnO/poly(amide–imide) nanocomposites based on levodopa-mediated diacid monomer

Hybrid nanocomposites (NCs) manufactured by distribution of zinc oxide (ZnO) nanoparticles (NPs) in poly[hydroxy(amide–imide)] (PHAI) are considered and produced by using an ultrasonic-assisted method. A novel monomer namely N,N′-pyromellitoyl-bis-l-(3,4-dihydroxyphenyl)alanine (NPDA) was synthesized by using levodopa as a starting material. The monomer structure was characterized by FT-IR and NMR spectroscopy. Reaction of the monomer containing pendent catechol moieties by a diamine by Yamazaki method provided the thermally stable PHAI matrix with well-designed units. FT-IR and 1H-NMR spectra confirmed the accomplishment of preparation step for the PHAI. The surface of ZnO NPs was functionalized with 3-aminopropyltriethoxysilane (KH550) coupling agent and donated a better dispersion and ornamental interactions with catechol functional units of PHAI matrix by hydrogen bonds. Provided NCs were characterized by FT-IR, X-ray powder diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetric analysis. The FE-SEM and TEM pictures confirm the coral-like structures for NCs. The FE-SEM and AFM analyses show the good dispersion of ZnO nanostructure in the PHAI matrix. The XRD patterns of NCs show the presence of crystalline ZnO NPs in amorphous PHAI matrix.