Emeraldine base-type

SERS spectra under 1064 nm excitation were studied for two forms of polyaniline, one of the emeraldine base type and the other of the emeraldine salt type to identify the chemical effects at the polymer/metal interface that are involved in the specific modifications of the SERS spectra. 19 refs. 

FIGURE 1.2. Molecular structure of widely used it-conjugated and other polymers (a) poly(para-phenylene vinylene) (PPV) (b) a (solid line along backbone) and it ( clouds above and below the a line) electron probability densities in PPV (c) poly(2-methoxy-5-(2 -ethyl)-hexoxy-l,4-phenylene vinylene) (MEH-PPV) (d) polyaniline (PANI) (d.l) leucoemeraldine base (LEB), (d.2) emeraldine base (EB), (d.3) pernigraniline base (PNB) (e) poly(3,4-ethylene dioxy-2,4-thiophene)-polystyrene sulfonate (PEDOT-PSS) (f) poly(IV-vinyl carbazole) (PVK) (g) poly(methyl methacrylate) (PMMA) (h) methyl-bridged ladder-type poly(jf-phenylene) (m-LPPP) (i) poly(3-alkyl thiophenes) (P3ATs) (j) polyfluorenes (PFOs) (k) diphenyl-substituted frares -polyacetylenes (f-(CH)x) or poly (diphenyl acetylene) (PDPA). 

The emeraldine base segment size distribution (/ (/ )) is calculated with the help of Ising type statistics on the base or salt sites using (8.12). 

Based on these results. Scheme m by which the EB-PAn/PVA composite responds to CO2 molecules is proposed. In the absence of CO2, the composite is insulating because EB-PAn is in the form of emeraldine base and no ionic species is present. In the addition of CO2 and humidity, however, carbonate ions are formed by the hydrolysis of CO2, and die incorporation of these ions into EB-PAn leads to die generation of the emeraldine salt-type polyaniline (ES-PAn). The concentration of carbonate ions equilibrate with the conceitradon of the atmospheric CO2, and the concentration of CO2 can be... 

Protonation of the emeraldine base can produce two types of ES crystal structures. The structures are denoted ES-I (from protonation of amorphous EB-I) and ES-II (from protonation of EB-II). 

Polyaniline forms a rich set of structures dependent upon the processing sequence and dopant [18,62,127-132]. Generally, doped polyaniline obtained from solution in the doped (conducting salt) form exhibits a local crystalline order of type emeraldine salt-I, ES-I. In contrast, polyaniline obtained by doping powder or films cast as the base form... 

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