Three-dimensional flower-like shaped Bi5O7I particles incorporation zwitterionic fluorinated polymers with synergistic hydration-photocatalytic for enhanced marine antifouling performance.

Herein, several novel composite films consisting of three-dimensional (3D) Bi5O7I flower-like shaped microsphere and zwitterionic fluorinated polymer (ZFP) were successfully fabricated with the aim of achieving high anti-fouling performance. The prepared Bi5O7I flower-like shaped microsphere particles with diameters in the range of 2∼3 µm were uniformly distributed on the surface and in the internal of ZFP. Benefiting from the hydration layer formed by the ZFP and the efficient photocatalytic performance of Bi5O7I flower-like microsphere, the resultant optimized Bi5O7I/ZFP composite film exhibited an excellent diatom anti-settling performance and a high antibacterial rate of 99.09% and 99.66% towards Escherichia coli and Staphylococcus aureus. In addition, the composite films possessed the strengthened visible light absorption, the effectively separation and transfer of the photo-induced electrons and holes, the large number of hydroxyl (OH) radicals and superoxide radicals (O2-) all in Bi5O7I/ZFP systems, all of which were beneficial for the photocatalytic antifouling activity. More importantly, the synergistic hydration-photocatalytic effect of the Bi5O7I/ZFP composite films are answerable for the improvement of the antifouling property compared to the control. Thus, the synergistic hydration-photocatalytic contribution of Bi5O7I/ZFP composite film will shows promise for potential application in marine antifouling.

Photocatalytic reactivities of Nafion-coated TiO2 for the degradation of charged organic compounds under UV or visible light.

Nafion (perfluorinated polymer with sulfonate groups)-coated TiO2 particles (Nf/TiO2) were prepared and their reactivities for the photocatalytic degradation (PCD) of charged organic substrates were investigated. The presence of Nafion adlayers drastically changed the positive TiO2 surface charge to a negative one over the entire pH range and significantly influenced the PCD kinetics and mechanisms. The UV-induced PCD of tetramethylammonium (TMA; cationic substrate) was greatly enhanced in the presence of Nafion adlayers on TiO2 because the ion-exchange sites within the Nafion can hold cationic substrates. On the other hand, despite the unfavorable electrostatic interaction between the Nf/TiO2 and anionic substrates, the PCD of dichloroacetate (DCA) and acid orange 7 (AO7) with Nf/TiO2 was not significantly inhibited. The visible-light-sensitized degradation of dyes was enhanced with Nf/TiO2 not only for cationic dyes (methylene blue (MB) and rhodamine B (RhB)) whose uptake on Nf/TiO2 is enhanced, but also for an anionic dye (AO7) that is less adsorbed on Nf/TiO2. The unexpected behavior in AO7 degradation seems to be related to the role of the Nafion layer in retarding the charge recombination. These observations indicate that Nf/TiO2 can enhance the PCD reactivity for cationic substrates without sacrificing the PCD reactivity for anionic substrates. In addition, it was found that the sensitized degradation of RhB followed a different path when the surface of TiO2 was coated with Nafion. The N-de-ethylation of RhB that leads to the generation of rhodamine-110 was a prevailing path with Nf/TiO2, whereas the cleavage of the chromophoric ring structure was dominant with pure TiO2. The effects of Nafion adlayers on the photoinduced electron transfer and PCD kinetics and mechanisms are discussed.

Branched fluoropolymer-Si hybrids via surface-initiated ATRP of pentafluorostyrene on hydrogen-terminated Si(100) surfaces.

Linear, branched, and arborescent fluoropolymer-Si hybrids were prepared via surface-initiated atom transfer radical polymerization (ATRP) from the 4-vinylbenzyl chloride (VBC) inimer and ClSO(3)H-modified VBC that were immobilized on hydrogen-terminated Si(100), or Si-H, surfaces. The simple approach of UV-induced coupling of VBC with the Si-H surface provided a stable, Si-C bonded monolayer of "monofunctional" ATRP initiators (the Si-VBC surface). The aromatic rings of the Si-VBC surface were then sulfonated by ClSO(3)H to introduce sulfonyl chloride (-SO(2)Cl) groups and to give rise to a monolayer of "bifunctional" ATRP initiators. Kinetics study indicated that the chain growth of poly(pentafluorostyrene) from the functionalized silicon surfaces was consistent with a "controlled" or "living" process. The chemical composition and functionality of the silicon surface were tailored by the well-defined linear and branched fluoropolymer brushes. Atomic force microscopy images revealed that the surface-initiated ATRP of pentafluorostyrene (PFS) had proceeded uniformly on the Si-VBC surface to give rise to a dense and molecularly flat surface coverage of the linear brushes. The uniformity of surfaces with branched brushes was controlled by varying the feed ratio of the monomer and inimer (VBC in the present case). The living chain ends on the functionalized silicon surfaces were used as the macroinitiators for the synthesis of diblock copolymer brushes, consisting of the PFS and methyl methacrylate polymer blocks.

High-speed MAS-NMR investigations on radiation-modified fluoropolymers.

Fluoropolymers possess an interesting combination of physical and chemical properties. In order to utilize these properties in combination with other materials, the compatibility of the fluoropolymers with those materials has to be improved by a suitable modification process. As one modification process the irradiation with high-energy electrons has been applied. High-speed MAS solid-state NMR has been used to characterize the structural changes in fluoropolymers resulting from the irradiation. The high MAS rotation frequencies, applied here, average the anisotropy of the chemical shift and the homonuclear dipolar coupling. Despite the fact that the electron irradiation results in a low concentration of modifications, the dynamic range of the solid-state NMR experiment is sufficient to detect and characterize the modifications.