Synthesis and Physical Properties of Highly Sulfonated Polyaniline

Abstract

Sulfonated polyaniline (SPAN) is a self-doped conducting polymer. It has a high water solubility and a novel pH-dependent DC conductivity that is of interest for fundamental science and also for applications in such areas as rechargeable battery and pH control technologies. We report here the extensive characterization and details of synthesis of a new form of sulfonated polyaniline (LEB-SPAN) which shows novel or significantly improved chemical and physical properties. LEB-SPAN has a high sulfur to nitrogen ratio (S/N) of ∼0.75, 50% larger than that previously reported for EB-SPAN, S/N ∼0.50. This change in composition leads to significant alteration of the properties including an order of magnitude increase in the room temperature DC conductivity to ∼1 S·cm-1, nearly double the solubility in water, and a completely different pH dependence of the oxidation potential (E 1/2). For LEB-SPAN the DC conductivity is unaffected by pH over the range 0 ≤ pH ≤ 14, strikingly different from the behavior of both parent polyaniline and EB-SPAN which become insulating for pH ≥3 and ≥7.5, respectively. Temperature-dependent DC conductivity and EPR measurements for LEB-SPAN reveal a lower activation energy for the conductivity and a higher density of states at the Fermi energy as compared with EB-SPAN. The dramatic differences in the pH dependence of the DC conductivity, cyclic voltammetry (CV), FTIR, and UV−vis results for LEB-SPAN and EB-SPAN are shown to be a consequence of the much higher S/N ratio in LEB-SPAN. We propose and describe a novel quasi-random oxidation model for the electrochemical oxidation of polyaniline and its derivatives at the microscopic level. This model quantitatively describes many of the phenomena and physical properties found in the polyanilines including the origin of the defect states and the in situ EPR signal during CV potential scans. Also the statistical nature of this model suggests its general applicability to the oxidation process of other conducting polymers. Computer simulations based on this model are presented and show good agreement with the in situ EPR/CV data reported earlier. In addition, other models are proposed to interpret the reported experimental differences in the pH dependence of E 1/2 among LEB-SPAN, EB-SPAN, and its parent polyaniline samples. Mechanisms for the new sulfonation route are proposed.

Electrical performance of conducting polymer (SPAN) grown on GaAs with different substrate orientations

“…Among the family of organic semiconductors, the semiconducting polymers have attracted the most attention for applications in electronic and optoelectronic devices, particularly due to their exceptional electrical properties and easy synthesis [2][3][4]. As a result, this category of polymers has been used in several applications such as organic light emitting diodes (OLEDs) [5,6], solar cells [7,8] As it is well known, the crystallographic orientation of the substrate has a significant effect on incorporation of impurities and defects and consequently on optical and electronic properties of III-V materials [28].…”

“…Among the family of organic semiconductors, the semiconducting polymers have attracted the most attention for applications in electronic and optoelectronic devices, particularly due to their exceptional electrical properties and easy synthesis [2][3][4]. As a result, this category of polymers has been used in several applications such as organic light emitting diodes (OLEDs) [5,6], solar cells [7,8], battery electrodes [9,10], photodiodes [11], energy storage [12], transistors [13], gas sensors [14], biosensors [15], radiation sensors [16], anti-corrosive coatings [17,18] and electromagnetic interference shielding [19].…”

“…This material is environmentally stable over a wide range of temperatures. It can be grown as thin films over large areas at low cost [3]. In addition, SPAN has a big advantage in electronic circuitry design [8] because it forms Ohmic contacts with metals used in microelectronic applications such as Al, Ag and Cu.…”

Materiais para cátodos de baterias secundárias de lítio

“…Têm sido obtidos vários derivados da polianilina, manufaturados através da substituição no monômero original, produzindo novos materiais ativos com propriedades físicas distintas da polianilina [102][103][104][105] . Um dos tipos mais interessantes de derivados são as chamadas polianilinas auto-dopadas; tais polímeros contêm grupos funcionais aniogênicos, aptos a interagir com átomos de nitrogênio positivamente carregados presentes na cadeia de polianilina, causando novos efeitos, diferentes daqueles apresentados por polímeros dopados com ânions em solução 106 .…”

Electrochemical Synthesis of Three-Dimensional Polyaniline Network on 3-Aminobenzenesulfonic Acid Functionalized Glassy Carbon Electrode and Its Application

“…Thus, in general, the redox potential of species to be oxidized and reduced by PAN is limited within the potential range in which PAN itself is electrochemical active; this restricts greatly its application in other fields, such as bioelectrochemistry, which normally requires a neutral pH environment. To extend its application in solutions with higher pH values, three kinds of methods have been explored and used widely: the first way of improving the pH dependence of PAN reactivity was performed by using the sulfonation of PAN with fuming sulfuric acid treatment to prepare the self-doped PAN, whose conductivity is independent of pH in the aqueous acid solutions of pH ≤ 7.5 [13,14]; the second way of extending the pH dependence of PAN electro-reactivity is to perform the polymerization of aniline in the presence of other organic acids, such as camphorsulphonic acid (CSA) [15], -naphthalenesulfonic acid (NSA) [16], 5-sul-phosalicylic acid (SPA) [17], dodecylbenzenesulfonic acid (DBSA) and p-toluenesulfonic acid (p-TSA) [18]; and the third method is via the synthesis of self-doped PAN by electrochemical or chemical copolymerization of aniline and its derivatives (ortho-, meta-substituted aniline) bearing ionogenic functionalities, such as sulphonic [19][20][21], carboxylic acids [19,22] and hydroxyl groups [23].…”