The structure of polypyrrole consists of long conjugated polymer backbone as shown in Fig. 1.2b. The polymer has resonance structures that resemble aromatic or quinoid forms. In this neutral state the polymer is not conducting and it conducts only when it is oxidised. Polypyrrole is an insulator but its oxidized derivatives are good conductors. The Conductivity ranges from 2 to 100 S/cm. The charge associated with the oxidised state is typically delocalised over several units and can form a radical cation (polaron) or a dication (bipolaron).
Polypyrrole is poorly crystalline, with crystalline regions randomly oriented and the polymer chains lying with the pyrrole rings coplanar to the surface . Actually polypyrrole obtained so far
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Polypyrrole is a conducting polymer which has non-degenerate conduction band in the ground state. The polarons and bipolarons are the dominant charge carriers in these polymers. The most widely accepted method of conductivity in these systems involve charge transport along the polymer chains, as well as hopping of carriers (holes, bipolarons). A common feature of intrinsically conducting polymers is the alternate double and single bond in the polymer backbone , referred as pi bond conjugation. The conductivity is due to four conditions namely, the existence of charge carriers, an overlap of molecular orbits to aid mobility of the carriers, mobility of pi bond and hopping of charges between polymer chains. These conducting polymers are similar to semiconductors with a filled valence band and an empty conduction band separated by energy gap. when polymers are doped new bands are created in the gap, making the paths for the electrons to move through these bands and increasing the conductivity of the materials. In the undoped form Polypyrrole is a insulator. The electronic and transport properties of the conducting polymers are mainly due to the major role of bipolarons. The positive charges commonly called as polarons created on the polymer backbone are responsible for electrical conductivity. The conductivity of polypyrrole depends on synthesis …show more content…
When the polymer is doped partially, islands of conducting material are developed, which are oxidized sites on the polymer chain. A small percentage of the sites form a network, yielding a small , finite DC conductivity. Hopping of charge carriers between favourable sites accounts for AC conductivity. Thus the conductivity is a combination of frequency dependent AC conductivity and DC conductivity. At higher level of doping, an increase in the network density through the polymer chain results in elimination of number of isolated sites which give rise to AC conductivity. So at the limit of very high doping the number of isolated sites is less and the DC conductivity dominates the total conductivity.
so that the conductometric data were treated by Fuoss–Shedlovsky method [11] by using a computer program, to evaluate the ion-pair association constants of the studied salts and to re-evaluate the limiting molar conductance (Λ0), where they proposed the following equation:
As found in the group lab, polar covalent substances are soluble in water due to the dipole-dipole attraction between water and the molecule. They are also soluble in ethyl alcohol for this same reason. Also, they are not conductors in H2O because there are no charged particles floating freely, they are elements, not ions. Lastly, they have a melting point between 1000C and 5000C due to the dipole-dipole forces within the molecule. In the independent lab, it was found that the substance in container 4 met most of the requirements for it to be classified as a polar substance. It was soluble in water and ethyl alcohol, it did not conduct electricity in H2O and had a melting point between 1000C and 5000C. Although, the chemical within this container was not soluble in ethyl alcohol and soluble in hexane. This could have been due to the ratio of the substance and volume of
In our study, a nanocrystalline PEDOT: PSS polymeric counter electrode was used instead of the Pt counter electrode to reduce the cost of the DSSC. We present a detailed study of the photovoltaic response as current-voltage (I-V) and C-V characterization of the DSSC based on PEDOT: PSS. The conduction mechanism and the negative capacitance of the studied cell are analyzed in
Properties of Solutions: Electrolytes and Non-Electrolytes The objective of this lab the type of compounds formed in many different solutions dissolved in water based on the conductivity of each. Procedure: Refer to handout entitled “Properties of Solutions: Electrolytes and Non-Electrolytes” Materials: Refer to handout entitled “Properties of Solutions: Electrolytes and Non-Electrolytes” Data & Observations: Solution Conductivity (μS/cm) A – CaCl2 9100 μS/cm A – AlCl3 11920 μS/cm A – NaCl 6280 μS/cm B – HC2H3O2 485 μS/cm B – HCl 15400 μS/cm B – H3PO4 6000 μS/cm B – H3BO3 10 μS/cm C – H2Odistilled 1 μS/cm C – H2Otap 790 μS/cm C – CH3OH 1 μS/cm C – C2H6O2 2 μS/cm Conclusion: 1.
When ionic compounds (compounds consisting of a positive cation and a negative anion stuck together by the attraction of the other’s charge) are dissolved in water, electrolytes are created. An electrolyte is a substance that conducts electricity when dissolved in water, while a non-electrolyte is one that cannot.3 In general, those compounds whose ions dissociate in greater amount and are in greater concentration are more conductive, or have more ability to transmit heat and electricity. We can demonstrate this dissociation of sodium chloride dissolved in water with the following chemical
PPV, otherwise known as polyphenylene vinylene are electric conductors that processed into tiny films which emit a bright fluorescent yellow light which could potentially be a replacement for LEDS in electronics. PPV is prepared from p-xylene-bis and the addition of acetonitrile-tetrabutylammonium tetrafluoroborate and from there, the product is treated with heat to eliminate diethyl sulfide, HCL, and ethyl sulfide to form the final product, PPV. Similarly, another method, called direct chemical polymerization, formed PPV but it was only in the form of powder which could not be turned into tiny films for commercial use. In lab, we learned that PPV precursor can be synthesized in a one step reaction from p-xylene using NBs. In the reaction with
* Co-polymers with randomly distributed side groups are versatile and therefore help give the desired physical and chemical properties. Properties Of The Primer Layer Amine groups in chains mean that ionic groups are produced when in contact with acid.
Two famous methodologies, the chemical or electrochemical oxidation of phenylenediamines yields the analogous poly(phenylenediamines) and their potential application for the removal of lead ions from water [1, 3, 11].
Polystyrene is made up of hydrogen and carbon. Hydrogen is a non-metal with the lowest electronegativity so when it bonds with carbon, the carbon will have a greater attraction for the bonding electrons than the hydrogen due to its greater electronegativity. As a result, the bonding electrons will be closer to carbon than hydrogen. The carbon will have a slight negative charge and the hydrogen will have a slight positive charge.
The major differences of these two chemical bonds are shown obviously in the lab. Metals has larger density values, higher hardness than polymers and able to conduct electricity while polymers is not able to. To understand the distinction in atomic bonding, one can utilize the knowledge in his
some polymeric materials a higher ratio of singlets can be generated. Electrons can quickly and easily decay from singlet excitons to the ground state (HOMO) which
However, their molar refractivity has to be maximized simultaneously in order to obtain a viable HRI material. The molar refractivity depends on the polarizability of the elements and moieties comprising the compound of interest (see Table 1).23–26 The fact that carbon has only a modest atomic polarizability results in the low RI values of typical carbon-based polymers. Highly polarizable heteroatoms and substituents (e.g., sulfur, phosphorus, bromine, iodine) can significantly improve the RI of the corresponding polymers. Hydrogen and strongly electronegative elements (such as oxygen and fluorine) have a low polarizability and consequently exhibit the inverse effect. A number of HRI polymers containing high mass fractions of RI-promoting elements
A polymer is a long chain of molecules made up of many repeating identical units called monomers. A polymer made from two or more repeating units of monomers are called copolymers (Smith et al., 2006). Monomers are often made up of Hydrogen and Carbon with extra elements such as Oxygen, Nitrogen and Chlorine, creating the backbone of the polymer. These can be made synthetically, such as polyethylene or occur naturally like cellulose, as are the polymers being investigated are. Polylactic acid is made naturally and Polypropylene is made synthetically. Polymers can be three dimensional networks which don’t melt such as epoxy resin, and are called thermoset polymers, two dimensional or one dimensional networks or chains which can be melted such as polypropylene called thermoplastic polymers
The cyclic potential sweep method was applied to aniline electropolymerization on stainless steel electrode in three different concentration of aqueous sulphuric acid solutions (0.5M H2SO4 , 1M H2SO4 and 2M H2SO4 ).The electrodeposited films of polyaniline were investigated and characterized using a simple cyclic voltammetry method to obtain information about the electrochemical properties of the deposited films. The polymerization of aniline on stainless steel via cyclic potential sweep method appears to be high performance for protection of metal anodic in corrosive aqueous media. Also it was found that the corrosive tendency increase with increasing the concentration of the acid and decrease with increasing the cycle number. Chronoamperometry method was used to investigate the electrochemical properties of the electrodeposited film of polyanilne.
As explained by IDTech Ex report that the flexible electronics market will reach over $76 billion by 2023[1],while the market for flexible, thin, stretchable and bendable batteries will grow to become about $471 million industry by 2026[2]. Additionally, the product is considered the most promising energy storage device with low carbon dioxide emission. The energy density of the lithium ion battery range between 120-170 Wh Kg-1 and 250-380 Wh l-1 more higher than Ni-Cd and Lead-acid[3]. LIB has three major electronically active components namely anode, electrolyte, and cathode. The anode is the negative electrode that releases electrons into an external circuit during a discharge process that involves the oxidation of chemical reactions. On the other hand, the cathode is the positive electrode that is reduced during a reaction. Notably, the lithium ions are stored within the cathode after a cell is discharged. Both cathode and anode stores energy while on charge, and releases it on discharge[4]. Cathode materials have relatively high electrochemical potentials while anode materials have low potentials. This design approach helps maximize the battery’s output voltage. The final active component of the LIB is the electrolyte. It is a mixture of a set of organic solvents containing disassociated lithium salts that enables Li+ transportation between the anode and the cathode. Besides, other complementary components, such as current collectors attached to the