Conducting Polymers Have Great Potential For Use In Electronics Applications Because Of Their Wide Range Of Electrical 1 (190.83 KiB) Viewed 10 times
Conducting polymers have great potential for use in electronics applications because of their wide range of electrical, electrochemical, and optical properties. An example of such a polymer is polyaniline (PANI), which is synthesized by oxidizing aniline (Compound 1, Figure 1). Because of various limitations in the synthetic production of PANI, there is interest in producing PANI enzymatically. 5-6²0-01 Compound 1 PANI Figure 1 The structure of Compound 1 and PANI Horseradish peroxidase (HRP) is a 44 kDa monomeric protein that contains a single iron(III) heme cofactor and two calcium ions. The heme iron is coordinated by a single histidine residue, and the calcium ions are coordinated by various Asp, Ser, Thr, Val, Gly, and Ile residues through both side chain and backbone interactions. The substrate binding site of HRP interacts with aromatic rings of incoming substrates. HRP catalyzes the oxidation of aromatic amines and phenols. The oxidation occurs at the ring substituent. The proposed catalytic mechanism involves the formation of a porphyrin-based cation radical through reaction with hydrogen peroxide as shown in Reaction 1. The aniline free radicals generated in the oxidation reactions undergo coupling to produce the dimer, and subsequent oxidation and coupling reactions produce the polymer. H₂O₂ + 2 Compound 1 HRP → 2H₂O + 2 Compound 1 radical Reaction 1 Polyanionic molecules can be used as templates in the HRP- catalyzed synthesis of PANI to ensure only the desired polymeric structure is obtained. The negative charge of the sulfonate (pK₂ = 0.7) in polystyrene sulfonate (PSS) interacts with the incoming aniline molecules (pK₂ = 4.6) and forces them into a conformation that results in a linear polymer. The best-performing PANI had a maximum conductivity of 5.0 x 10-³ (2.cm)-¹.
What is the resistivity of the best-performing PANI described in the passage? A. 0.002 Q2.cm B. 50 cm C. 200 D. 500 cm cm
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