Figure 4. Density measurements for undoped and doped PPy.

(a) Average density measurements (n=3 matrices, 1500 snapshots for each matrix) for undoped PPy matrices generated by thermal annealing, undoped PPy matrices generated by potential scaling, and PPyCl matrices made through a mutation process. Both thermal annealing and potential scaling approaches consistently produced matrices of similar density. For doped PPy, we observed a swelling in the material that caused a slight decrease in density. (b) Average density measurements (n=3 matrices, 500 snapshots for each matrix) for PPyCl where electrostatic charge parameters have been scaled up or down. CNDO charges taken from Cascales et al. [13] were also used for comparison. For fixed charge models, scaling charge parameters is one way to account for polarization. We found that scaling the electrostatics of PPyCl has a non-trivial effect on polymer density, with larger charge parameters producing denser films. (c) Average density for crystalline PPyCl (n=1 matrix, 1500 snapshots) demonstrates that chain packing greatly affects bulk density.