Abstract
Original telomers based on vinylidene fluoride (VDF), CnF2n+1(VDF)m(CH2CH2)pI, where n¼4 or 6, m¼5–23 and P¼0 or 1, were synthesized, and the piezoelectric properties of the materials were investigated. Low-molecular-weight polyvinylidene fluorides (PVDFs) were prepared in good yields by iodine transfer polymerization of VDF. The polymerization of VDF was conducted in the presence of 1-iodoperfluoroalkanes (C4F9I or C6F13I) and bis(4- ert-butylcyclohexyl) peroxydicarbonate, which were used as a chain transfer agent and initiator, respectively. The microstructure of VDF telomers was carefully characterized by 1H and 19F nuclear magnetic resonance (NMR) spectroscopy to assess the average molecular weight and the percentage of CH2CF2I functionality (that ranged from 47 to 86%). X-ray diffraction patterns of these telomers indicated that PVDFs with o6 VDF units displayed the a-form. Alternatively, telomers containing a higher amount of VDF possessed both a- and b-forms. Ethylene endcapping of CnF2n+1(VDF)mI was also successfully achieved in high yield, and the telomeric precursors were converted quantitatively. Moreover, three VDF telomers were vaporized into films, and the piezoelectric properties of the materials were assessed. The results revealed that C6F13(VDF)23I and C4F9(VDF)21I telomer films displayed piezoelectric responses (d33¼268 pCN1) and high remanent polarizations (Pr¼98.2 and 93.4mCm2, respectively). In addition, C4F9(VDF)21C2H4I exhibited interesting piezoelectric properties (Pr¼89.9mCm2).