*3.1. Modeling*

The structure of polystyrene and fluorinated polystyrene were drawn using Avogadro and optimized using LAMMPS [16,17]. We applied the reactive hydrocarbon potential AIREBO and optimized its structure at room temperature [18]. The simulation size was 40 × 40 × 40 cubic Å for one cell. The polystyrene in on cell was shown in Figure 2.

**Figure 2.** Polystyrene with 322 atoms.

We applied a reactive force field potential to consider the fluorine atoms [19,20]. The fluorinated polystyrene, 1F-PS(poly(4-fluorostyrene) and 5F-PS(poly(2,3,4,5,6-pentafluorostyrene)), are shown in Figure 3. The length of each atom was calculated and compared with the cut-off distance of each bond using the same method as that for polystyrene. We performed the simulation ten times in 10 cells under the same conditions.

**Figure 3.** Fluorinated polystyrene: (**a**) 1F-PS(poly(4-fluorostyrene)) (**b**) 5F-PS(poly(2,3,4,5,6- pentafluorostyrene)).
