Determination of crystal structure of polyaniline and substituted polyanilines through powder X-ray diffraction analysis

Polyaniline (PANI), poly(m-aminophenol) (PMAP) having a phenolic group as aromatic substituent and poly(m-nitroaniline) (PMNA) having a nitro group as aromatic substituent were synthesized by oxidative polymerization from their respective monomers. The degree of crystallinity, crystallite size, inter-chain separation and d-spacing were calculated from the experimental results, whereas crystal symmetry, space group, unit cell dimensions, agreement factors and molecular arrangement were derived from the experimental results using FullProf and FOX v. 1.7. OSVN software. PMAP shows the most regular or ordered structure having the highest degree of crystallinity, whereas the lowest percent crystallinity and the least ordering of the molecules were observed for PMNA. The order of the crystallite size of these polymers is PMAP > PANI > PMNA. It was found that due to the presence of aromatic substitutions on polyaniline the crystal symmetry, space group, unit cell dimension and molecular arrangement in the unit cell are changed. A positive serial correlation between observed and calculated profiles for all these polymers was observed and the goodness of fit is 2.5 for PANI and 1.5 for PMAP and PMNA. (C) 2008 Elsevier Ltd. All rights reserved.