Computational and Experimental Analysis of Functional Materials

Oleksandr V. Reshetnyak, Gennady E. Zaikov, Oleksandr V. Reshetnyak, Gennady E. Zaikov

• Editore: Apple Academic Press
• Anno: 2017
• ISBN:
  9781315342139
• Edizione: 1
• Argomento: Sciences biologiques
• Categoria: Science générale

This book looks at the synthesis of polyaniline by different methods, under different conditions, for various applications, and presents studies of its properties by a wide range of the modern physic-chemical methods. The book provides a comprehensive analysis of experimental results from the point of view of the correlations in the triad synthesis conditions–structurephysico–chemical properties. It combines the results of experimental investigations and original methodology of the description of physical–chemical and electrochemical phenomena at interface surfaces, showing an influence of such phenomena on the applied aspects of the polyaniline and nanocomposites on its basis applications.

CHAPTER 1

POLYANILINES: THE ROLE OF PARTICLES OF RADICAL NATURE IN OBTAINING OF POLYMERS/COPOLYMERS WITH A SYSTEM OF CONJUGATED π-BONDS

O. V. RESHETNYAK¹, M. M. YATSYSHYN¹, and L. I. BAZYLYAK²

¹Department of Physical and Colloid Chemistry, Faculty of Chemistry, Ivan Franko National University of Lviv, 6 Kyryla & Mefodia Str., Lviv 79005, Ukraine

²Department of Physical Chemistry of Fossil Fuels, L. M. Lytvynenko Institute of Physical–Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine, 3a Naukova Str., Lviv 79053, Ukraine

Corresponding author: [email protected]

CONTENTS

Abstract

1.1 Introduction

1.2 The Mechanism of Oxidative Polymerization of Aniline in Aqueous Solutions

1.3 An Impact of the Substituent’s Nature on Mechanism of the Synthesis, Structure, and Properties of Polyanilines

1.4 Chemical Synthesis of Polyluminol

1.5 Conclusions

Keywords

References

ABSTRACT

The mechanism of the initial stages of oxidative polymerization of aniline (An) and its derivatives with the formation of conductive polymers with the system of conjugated π-bonds has been analyzed. It is shown that both during chemical (in the presence of peroxydisulfate anions) and electrochemical polymerization, the process is initiated by the cation-radicals of the initial monomer, which then recombine in accordance with the type “head to tail.” The obtained dimers represent by themselves the structural units of the future polymeric chain, and then they can take part in similar chain of the transformations. In the process of polymeric chain propagation, the molecules with varying polymerization degree can participate, because their reactivity is determined by the presence of the end amino-groups, and, therefore the oxidative polymerization is typical polyaddition process. On example of nitro-and oxymethyl-derivatives, the impact and position of the substituent in the aromatic ring on the reactivity of the aniline derivatives in the reaction of oxidative polymerization were evaluated. On the basis of spectral studies and elemental analysis, the most likely structures of the obtained polymeric anilines, including the polyluminol, were determined. It was shown that in the case of polyanilines (PAn) obtained by chemical method, regardless of the nature of the initial monomer the final product represents by itself a form of emeraldine salt.

1.1 INTRODUCTION

The discovery of polymers possessing own electroconductivity due to the presence of the system of alternant σ-and π-bonds results in the occurrence and the development of new fundamental areas of researches in chemistry, physics, materials science, etc.^1–3 Electroconductive polymers (ECPs) combine high flexibility and plasticity, typical for the polymers with high electroconductivity whose value may approach to the conductivity of metals. This property of ECPs has led them to be often called as “synthetic metals.” Among the large number of modern organic and inorganic materials, the ECPs are valued as “strategic” materials that have become the objects of intense researches in the laboratories of the world’s leading scientific centers and major industrial corporations.⁴

Polyaniline (PAn) and polymers based on its derivatives occupy an especial place among the ECP. Due to the special electronic spatial structure of aniline and its derivatives, their polymers have a wide range of physical and chemical properties, such as the ability to the reversible oxidation–reduction, long-continued resistance to not only moisture or air, but also so much more aggressive media. The combination of low prime cost with ease of synthesis makes such materials indispensable in molecular electronics, biochemistry, medicine, chemical current sources, etc. The color of PAn depends on the pH value and on the applied potential, and can vary from light yellow (at pH = 1 and the electrode potential E = −0.2 V) to purple-red (pH = 4 and E = +1.4 V), passing through yellow, green, dark-blue, black, and many their tints.^{5, 6} This property of PAn was the basis for its use as pH indicators,^{5, 7} in electrochromic^{6, 8–11} and electroluminescent^{12, 13} devices. PAn layers possess good corrosion properties during protection of steel,^14–17 zinc,¹⁸ copper,¹⁹ aluminum, and its alloys (Chapter 8). Thin layers of PAn are used in molecular electronics,^{2, 20} as detectors and dosimeters of γ-radiation²¹ in the manufacture of various types of sensor devices for determining pH,^{22, 23} viruses,²⁴ and also important analytes such as ammonia,²⁵ H₂O₂,²⁶ NO₂,²⁷ CO,²⁸ HCN,²⁹ H₂,³⁰ CH₄,³¹ glucose,³² carbamide,³³ etc. PAn and its derivatives are used as cathode materials in chemical sources of electrical energy^{34, 35} and electrochemical supercapacitors.^36–39

The polymerization of aniline is very easily carried out chemically in aqueous acidic solutions using as oxidizing agents the peroxide compounds (in particular, peroxydisulfates,^40–42 hydrogen peroxide,^{7, 43} benzoyl peroxide⁴⁴), the ions in higher oxidation level (Fe³⁺, Ce⁴⁺, Cr₂O₇²⁻, IO₃⁻, ClO₂⁻, and VO⁻₃),^45–50 the oxides of transition metals (V₂O₅,⁵¹ WO₃,⁵² MnO₂, and PbO₂⁵⁰) and enzymes,^53–56 etc. PAn layers on the surface of metals or semiconductors were also obtained by the method of vacuum deposition^{57, 58} or by the polymerization in plasma.^{59, 61} However, often the method of electrochemical polymerization is used due to the opportunity to get thin polymeric layers on the surface of the conductive substrate. It has been reported about obtaining of PAn on the platinum electrode during its polarization under potentiodynamic⁶² or galvanostatic⁶³ conditions in both aqueous^62–64 and organic⁶⁵ media. In all cases, the structure and properties of the polymerizates differ significantly, mainly due to varying degrees of protonation of nitrogen atoms in the polymeric chain. This difference leads to the v...