Molecular weight determinaiton of polyaniline

Summary form only given. The molecular weight (MW) of differently synthesised samples of polyaniline (PANI) is determined by: GPC, viscometry and light scattering (LS). The studied samples were prepared by: (1) chemical synthesis in HCI or other organic acids, in default of (NH/sub 4/)/sub 2/S/sub 2/O/sub 8/, (2) chemical synthesis with an excess of FeCl/sub 3/, (3) electrochemical synthesis in HCI and in NH/sub 4/F.2.35HF eutectic. As proved by dynamic LS, emeraldine base dissolved in NMP shows a strong aggregation, leucoemeraldine much less, so that accurate MW determinations by GPC are made on the latter one dissolved in 2% v/v hydrazine in NMP. The as-synthesised PANIs show a bimodal distribution of MW which may be suppressed by extraction of the low MW components. As determined by viscometry in 95% H/sub 2/SO/sub 4/, the stifftess of the chains progressively increases with the increase of the oxidation degree. The M/sub w/ of PANI synthesised by the methods (1) and (2) (vs PS standards) is in the region of 50,000. The M/sub w/ of PANI synthesised by the method (1) using organic acids is in the region of 12,000. The different MW distributions will be presented and correlated with the conditions of synthesis.