Opportunities and Challenges in the Use of TiO2 Nanoparticles Modified with Citric Acid to Synthesis Advanced Nanocomposites Based on Poly(Amide-Imide) Containing N,N′-(Pyromellitoyl)-bis-L-leucine Segments

In this study, the goal was the preparation, characterization, and surface morphology of poly(amide-imide)/TiO₂-citric acid nanocomposites (PAI/TiO₂-CA NCs). Owing to the high surface energy and tendency for agglomeration, the surface of TiO₂ nanoparticles was modified with citric acid. Then poly(amide-imide) was synthesized by direct polycondensation reaction of N,N′-(pyromellitoyl)-bis-L-leucine diacid with 4,4′-diaminodiphenylmethane by triphenyl phosphite and tetra-n-butylammonium bromide as a green medium. The attained polymer and modified TiO₂ nanoparticles were used to prepare PAI/TiO₂-CA NCs through ultrasonic irradiation. The resulting PAI/TiO₂-CA NC was characterized with FT-IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis.