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Polymer, Vol.149, 1-12, 2018
From Parkinson's chemotropic agent L-dopa to thermally resistive carbonaceous nanocomposite of a new catechol-grafted poly(amide-imide)
N,N'-Pyromellitoyl-bis-L-(3,4-dihydroxyphenyl)alanine was synthesized, as a new diacid monomer, from condensation reaction of t-dopa and pyromellitic anhydride. Polycondensation of this chiral monomer with the commercially available 4,4'-diaminodiphenylsulfone was achieved by using triphenylphosphite, as coupling agent, and calcium chloride, as dehydrating agent, in a mixture of N-methyl-2-pyrolidone and pyridine, giving a fairly high yield of a novel optically active poly(amide-imide) (PAI). This catechol containing PAI shows excellent adhesion to carboxylated carbon nanotubes, as forcing it to adopt a semi-crystalline structure in the interface with the nanotubes and thereby results in formation of a thermally stable and nearly homogeneous nanocomposite. FT-IR study revealed that much of this adhesion arises from H-bonding of the carboxylated nanotubes with the carbonyl groups of the PAL The uniform distribution of the nanotubes in the PAI matrix was confirmed by FE-SEM and TEM micrographs of their nanocomposite. Thermogravimetric analysis of the PAI and its nanocomposites with 5, 10, and 15 wt% of carboxylated carbon nanotubes indicates that their decomposition occur in the temperature range of 347-365 degrees C. The limiting oxygen indices for the PAI and its nanocomposites were found to be in the range of 37.9-43.1. The polymer and its nanocomposites were characterized by additional techniques. (C) 2018 Elsevier Ltd. All rights reserved.
Keywords:L-Dopa;Catechol containing polymer;Nanocomposite;Thermal stability;Chiral poly(amide-imide)