Nitrification Of Polyaniline And Polymerization Of Nitroaniline

Chiral polyaniline is a new type of conductive polymer, which has a wide range of applications in many fields such as asymmetric synthesis and chiral separation. However, it also has many limitations such as poor solubility and so on. Recently, chiral derivatives of polyaniline have been subjected to extensive research due to their unique physicochemical, optical, and electrical properties. In this thesis, polyaniline derivatives with nitro groups have been synthesized via two different routes, i.e. nitrification of polyaniline as well as oxidation polymerization of nitroaniline monomer.Polyaniline nanoparticle agglomerates have been prepared by oxidation polymerization method. The resulting polyaniline were characterized with scanning electron microscope and infrared spectroscopy techniques, followed by acylation of amino groups with 4-methylphenylsulfonyl chloride in the solution of N-methyl pyrrolidone (NMP). Subsequently, the acylation product was subjected to nitrification using concentrated H2SO4 and HNO3 mixture in the presence of NMP. The results show that both the morphology and visible optical response range of the starting polyaniline can be changed by this method.Oligomers of m-nitroaniline and o-nitroaniline monomers have been synthesized by the oxidation polymerization method. The reaction conditions were investigated in detail such as reaction time, temperature, polarity and pH of solution, initiators, oxidizers, and the form of feedstock, and so on. The resulting product was characterized with X-ray powder diffraction, ultraviolet-visible light spectroscopy, scanning electron microscope, infrared spectroscopy, matrix-assisted laser desorption/ionization time-of-light mass spectrometry (MALDI-TOF-MS), and circular dichroism (CD) techniques. The results show that:(1) The polarity of solution has important impact on morphology and chirality of the product. One-dimensional of chiral oligomers can be obtained in the mixture of acetonitrile with distilled water (1:2, v/v).(2) Morphology and chirality of the product have also been influenced by reaction temperature and time. The lengths, diameters, chiralities, and yields of the product increase with increasing temperature to 25°C and time to 3 days.(3) Morphology, chirality, and molecular weight of the product have also effected by the molar ratio of oxidation to nitroaniline monomer. The lower molar ratio of oxidizer to monomer (1:4) results in lower chirality, whereas the higher ratio of 2:1 leads to destruction of one-dimensional structure of the product. A suitable molar ratio of oxidizer to monomer is 1.2:1. The molecular weight of the product increases with increasing the content of oxidizer. In addition, a better chirality can be acquired by quickly adding (NH4)2S2O8 aqueous solution into the reaction media.(4) The chirality of the product can be enhanced to 7×10~4 degree·cm~2·decimole-1 by adding chiral organic acid into the reaction system. However, the increase in chirality is not dramatic in comparison with that of 5×10~4 degree·cm~2·decimole-1 without chiral acid.