Crystalline structure and transition behavior of recrystallized-irradiated P(VDF-TrFE) 65∕35 copolymer

The effect of recrystallization on the crystalline structure and properties of P(VDF-TrFE) $65∕35\mathrm{mol}\%$ samples that had previously been irradiated with high-energy electrons at doses of 60, 85, and $100\mathrm{Mrad}$ was studied. The crystallinity of the recrystallized samples was found to be lower than that of corresponding irradiated samples and the size of the crystalline regions in the recrystallized samples was smaller. For 60- and $85\text{‐}\mathrm{Mrad}$ irradiated samples, the crystalline regions in the recrystallized samples contained more $T_{m>3}$ conformations than in the corresponding irradiated samples, while for $100\text{‐}\mathrm{Mrad}$ irradiated samples, the crystalline regions in the recrystallized samples had fewer $T_{m>3}$ conformations. Based on their melting and structure transformation behaviors, the crystalline regions in the unrecrystallized irradiated samples have a much higher surface energy, probably originating from the compressive stress induced by crosslinking on the surface of the crystalline regions. Although the recrystallized samples have a lower surface energy, the crosslinking caused the crystalline regions in the polymer to have a partially ordered region on the surface of the crystalline regions. This partially ordered surface, i.e., the interfacial layer, results in a high polarization level in the recrystallized samples. Additionally, the recrystallized sample has a lower dielectric loss. These findings combined to make such recrystallized polymers strong candidates for use in applications requiring high-performance electroactive polymers.