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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Polymer (Guildf). 2010 Oct 1;51(21):4985–4993. doi: 10.1016/j.polymer.2010.08.024

Figure 2. Conformational energy profile and probability distribution for (a, c) undoped PPy and (b, d) doped PPyCl.

Figure 2

Torsion angle is defined such that zero is the cis configuration with the nitrogens on the same side. In a relaxed state, (a) undoped PPy does not adopt a planar backbone conformation, but rather an anti configuration at ±148°. (b) PPyCl, however, has a very rigid backbone with minima at 0° and 180°. Note that the 15 kcal/mol energy difference between 0° and 180° for PPyCl is from electrostatic interactions with the dopant, not from a torsion contribution. As shown in (d), bulk amorphous PPyCl adopts a roughly equal torsion angle distribution between cis and trans conformations. The torsional energy barrier of doped PPy is an order of magnitude greater than that of undoped PPy. For comparison, the condensed phase backbone distribution (c, d), which should be inversely proportional to the torsion energy, is also shown here. Potential scaling and thermal annealing approaches yielded similar backbone distributions for undoped PPy. For PPyCl, pre-packed crystals were mostly constrained to the trans configuration.