Molecular order polyaniline synthesis

Parameters such as, synthesis medium (HCl, camphor sulfonic add (CSA) or dodecylbenzene sulfonic acid (DBSA)), molar ratio aniline/oxidant, method for oxidant addition, temperature, polymerization duration, dedoping conditions will have effects on polymer properties in terms of yield, chain length, effective conjugation, defects rate, and electrical properties. Temperature was kept to 0 C, -30 C or -40 C and reactions were stopped after various durations in order to control the molecular weight of samples. Polymerization durations were varied from 1 hour to 5 days and depended on the reaction temperature. The inherent viscosities of the polyanilines (Pani) were determined at 25 °C in 0.1%w solutions in concentrated sulfuric acid (95 %), using an Ubbelohde viscometer. For instance, high viscosity samples (1.4 dl/g) were obtained after 3 days at -40 °C vsMe low viscosity samples (0.6 dl/g) were obtained after 1 hour at 0 A relationship was found between polymerization duration and inherent viscosity for polymers synthesized at low temperature (- 40 °C). Inherent viscosity increases from 0.6 to 1.4 when duration of polymerization increases from one to five days. In the case of synthesis at 0°C no correlation was obtained between duration of polymerization and inherent viscosity. A careful control of other parameters (synthesis medium, molar ratio aniline/oxidant, method for oxidant addition) have permitted to get samples with inlierent viscosities ranging from 0.55 to 2.1 dl/g in a reproducible way. 

Based upon the comparison of the experimental results with theory, it is clear that for polyaniline increased molecular weight will lead to enhanced electrical conductivities. Furthermore, since the transport is currently limited by disorder, it may be possible to achieve a major increase in electrical conductivity (by a factor of order N, the number of monomers in a typical macromolecular chain) with improved chain extension and alignment as a result of post-synthesis processing. 

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