Acid doping hydrogen bond

One of the problems associated with the use of heterocycles is that the intrinsic concentration of protonic charge carriers can only be moderately increased through acid doping (also see Section 4.3). This is particularly the case when the dynamics within the hydrogen-bonded domain is highly constrained through immobilization (especially in fully polymeric systems), which is probably the direct consequence of a reduced dielectric constant. This also leads to a further increase of the Haven ratio... 

Different substituents may be present on the homocyclic moiety. The properties of PANI depend on the presence of the hydrogen bond (also arising from doping substances, such as salicylic acid) as well as on the protonation to form salts210. 

The availability of the coherent proton tunneling and cooperative proton tunneling and transfer of four protons in hydrogen bonds of benzoic acids crystals (including dye doped) have been revealed by Trommsdorff and collaborators [12,13] by reading the electron spectra of the crystals. 

The formation of hydrogen bonds between the carboxylic acid groups of the functionalized liquid crystal copolymers and the pyridine portion of the dopants leads to stable, none separating mixtures. In mixtures containing up to 30 % of the dopants no separation was observed. Induction of a nematic mesophase is observed in the case of a smectic polymer matrix doped with low molecular weight photochromic dyes. 

For phosphoric acid-doped polybenzimidazole membranes with an intermediate Ap Ta (3.5), hydrogen bonds are likely formed as shown by infrared spectroscopy [61, 62] and molecular dynamic simulation [63]. The overall proton conductivity of the acid-doped membranes is at least an order of magnitude lower than that of pure phosphoric acid due to the presence of the solid polymer phase. The polymer does not seem to interrupt the extensive hydrogen bond network of the phosphoric acid, though it does decrease the percolation within the liqmd-like part of the phosphoric acid domain. As a result, the proton conducting mechanism remains the same, i.e., primarily via the Grotthuss... 

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