Abstract
A series of three fluorinated copolymers (FP) based on vinylidene fluoride (VDF) were involved in the preparation of original FP / anatase titanium oxide (an-TiO2), and FP / silica / an-TiO2 nanocomposites. These FP copolymers were prepared by conventional free radical copolymerization of VDF with various functional fluorinated comonomers such as F2C=CFCO2Me, FCH=CFCO2H, and F2C=CFC3H6OCOCH3 in good yields (> 60%) and had number average molecular weights of ca. 50,000 g.mol-1. Anatase titanium oxide in the FP / an-TiO2 nanocomposites underwent an effective modification into rutile polymorphism after calcination at 1000 oC. Although the parent an-TiO2 nanoparticles changed completely into rutile nanoparticles after calcination at 1000 oC, an-TiO2 embedded in the FPs / silica / an-TiO2 nanocomposites retained their structures without any phase transformation into rutile, due to locking the Ti-O species at the interface of TiO2 domains by the Ti-O-Si units, whose lattice can be formed by the interaction of silica with an-TiO2 nanoparticles. Even after such a thermal treatment, these nanocomposites displayed a higher photocatalytic activity for the discoloration of methylene blue as well as those of the corresponding nanocomposites before calcination, although the original an-TiO2 nanoparticles could not exhibit a photocatalytic ability after calcination. Among these nanocomposites based on VDF-containing copolymers, poly(VDF-co-CF2CFCO2CH3)/SiO2/an-TiO2 before and after calcination displayed better photocatalytic properties than those of the other FP nanocomposites. More interestingly, this FP /silica / an-TiO2 nanocomposite even after calcination at 1000 oC was able to preserve the same photocatalytic activity as that before calcination. In addition, these FP/TiO2 and FP/SiO2/TiO2 composites exhibited high thermal stability up to 800 °C with a loss weight of 2 % (or ca. 14 % for the acidic FP) only.