*2.1. Materials*

The styrene monomer, 2,3,4,5,6-pentafluorostyrene, tetrahydrofuran and di-tert-butyl peroxide (DTBP) as an initiator for polymerization were purchased from Sigma-Aldrich Korea (Seoul, Republic of Korea). 4-fluorostyrene was purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan). All commercially available reagents were used as received without further purification.

#### *2.2. Determination of Average Molecular Weight Sample Preparation and γ Radiation Experiments*

Polystyrene (PS) and fluorinated styrene (1F-, 5F-PS) were synthesized as per a procedure described in the literature with slight modifications (Figure 1) [15]. The styrene monomer (10.5 g, 0.1 mol) was suspended in 10 mL of tetrahydrofuran (THF) and 1.42 g (0.01 mol) of di-tert-butyl peroxide (DTBP) was added. The polymerization was carried out at 100 ◦C for 18 h, at which point the solution is cooled to room temperature (20 ◦C). The reaction product (PS) was precipitated in a solution of methanol (200 mL), vacuum-filtered, and dried at 60 ◦C for five days to evaporate the remaining solvent. To synthesize the fluorinated styrene, the same procedure as described above was used with 12.2 g (0.1 mol) of unit 4-fluorostyrene to the 1F-PS and 9.7 g (0.05 mol) of unit 2,3,4,5,6-pentfluorostyrene to the 5F-PS, respectively.

Prior to gamma irradiation, the prepared samples were packed in glass vials. After that, gamma irradiation was performed with respective irradiation doses (25, 50, 75, and 100 kGy) at a dose rate of 10 kGy/h. The Co-60 source (MDS Nordion, Ottawa, Ontario Canada, IR 221 n wet storage type C-188) was located at the Korea Atomic Energy Research Institute (KAERI), Jeongeup-si, Korea.

#### *2.3. Determination of Average Molecular Weight*

Changes in the molecular weights of the irradiated PS, 1F-PS, and 5F-PS were determined by gel permeation chromatography (GPC, Breeze system, Waters, Milford, USA) with the eluent of CHCl3 at a flow rate of 1.0 mL/min at 40 ◦C. This equipment consisted of a Water 1515 Isocrylic HPLC pump, Water 2414 reflective index detector, Phenogel column 5 μm (300 × (4.6 mm)), and calibrated with polystyrene standards (Shodex, SM-105, and SL-105).

**Figure 1.** Preparation of Ps, 1F-PS(poly(4-fluorostyrene)) and 5F-PS(poly(2,3,4,5,6-pentafluorostyrene)).

#### **3. Theoretical Study of Scissionning Reactions**
