Insertion of novel optically active poly(amide-imide) chains containing pyromellitoyl-bis-L-phenylalanine linkages into the nanolayered silicates modified with L-tyrosine through solution intercalation

Abstract

In the present investigation, for the first time, functional optically active poly(amide-imide) (PAI)/organonanosilica bionanocomposite films were successfully fabricated through solution intercalation technique. At the start, Cloisite Na⁺ and protonated form of l-tyrosine amino acid were used for the preparation of the novel chiral organoclay via ion-exchange reaction. Then, PAI containing phenylalanine amino acid was synthesized via solution polycondensation of N,N’-(pyromellitoyl)-bis-phenylalanine diacid chloride (5) with 4,4′-diaminodiphenylsulfone (6). This polymer was end-capped with amine end groups near the completion of the reaction to interact chemically with organoclay. Finally, PAI/organ-nanosilica bionanocomposites films containing 5, 10 and 15% of organoclay were prepared via solution intercalation method through blending of organoclay with the PAI solution. The nanostructures and properties of the PAI/organoclay hybrids were investigated using Fourier transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetry analysis (TGA) techniques. XRD, FE-SEM and TEM results revealed the formation of exfoliated and intercalated organoclay platelets in the PAI matrix. TGA results indicated that the addition of organoclay into the PAI matrix increases in the thermal decomposition temperatures of the resulted bionanocomposites. The transparency of the nanocomposite films decreased gradually by the addition of organoclay, and the films became semitransparent as well as brittle at high loading of organoclay. Mechanical data indicated improvement in the tensile strength and modulus with organoclay loading. The film containing a 10 wt.%. of organoclay had a tensile strength of the order of 85.24 MPa relative to the 67.52 MPa of the pure PAI.