Recent advances in fluorinated polymers:synthesis and diverse applications

Fluorinated polymers exhibit a unique combination of attributes,including chemical inertness,low surface energy,exceptional weather resistance,and intriguing electrical properties.This mini review provides an overview of recent advancements in the research of fluorinated polymers,highlighting the development of synthetic strategies for novel fluorinated polymers and their diverse applications in various fields.Traditional fluorinated polyolefins can be modified through chemical methods to produce functional materials.Copolymerization of fluorinated olefins with non-fluorinated monomers effectively addresses synthesis challenges,yielding main-chain fluoro-containing polymers with specific functional groups.Additionally,recent studies have revealed that free radical(co)polymerization of fluorinated(meth)acrylate monomers leads to new fluorinated polymers with enhanced solubility,processability,and structural diversity.Capitalizing on these new synthetic strategies,a range of fluorinated polymer materials has been developed for a multitude of applications,including flexible electrodes,alternating current(AC)electroluminescent devices,energy storage capacitors,triboelectric nanogenerators,and lithium batteries.With their customized structures and excellent properties,fluorinated polymers hold significant promise to uncover more potential applications in the era of flexible and wearable electronics.

Arrayed Lensed Fibers Collectively Fabricated Utilizing UV-Curable Fluorinated Polymer

A novel fabrication method for lensed fiber array has been proposed utilizing UV-curable fluorinated polymer, whose refractive index is matched to fused silica. The structure is composed of three segments; single mode fiber, coreless silica fiber and UV-curable polymer lens-tip. Flexible control of the curvature of lens-tip was realized by control of deposited volume of the liquid polymer and free-space interconnection performances are characterized.

Anisotropic self-diffusion of fluorinated poly(methacrylate) in metal-organic frameworks assessed with molecular dynamics simulation

Utilizing the periodically structured metal-organic framework （MOF） as the reaction vessel is a promising technique to achieve the aligned polymer molecular chains, where the diffusion procedure of the polymer monomer inside MOF is one of the key mechanisms. To investigate the diffusion mechanism of fluorinated polymer monomers in MOFs, in this paper the molecular dynamics simulations combined with the density functional theory and the Monte Carlo method are used and the all-atom models of TFMA （trifluoroethyl methacrylate） monomer and two types of MOFs,[Zn2（BDC）2（TED）]n and[Zn2（BPDC）2（TED）]n, are established. The diffusion behaviors of TFMA monomer in these two MOFs are simulated and the main influencing factors are analyzed. The obtained results are as follows. First, the electrostatic interactions between TFMA monomers and MOFs cause the monomers to concentrate in the MOF channel, which slows down the monomer diffusion. Second, the anisotropic shape of the one-dimensional MOF channel leads to different diffusion speeds of monomers in different directions. Third, MOF with a larger pore diameter due to a longer organic ligand,[Zn2（BPDC）2（TED）]n in this paper, facilitates the diffusion of monomers in the MOF channel. Finally, as the number of monomers increases, the self-diffusion coefficient is reduced by the steric effect.

Identification of tartrazine and sunset yellow by fluorescence spectroscopy combined with radial basis function neural network

The fluorescence spectra of synthetic food dyes of sunset yellow and tartrazine are analyzed. The fluorescence peak wavelengths of sunset yellow and tartrazine are 576 and 569 nm, respectively, while the fluorescence spectra widths are 480-750 and 500 750 nm induced by ultraviolet light between 310-400 nm. The fluorescence spectra of sunset yellow overlap heavily with those of tartrazine, so it is difficult to distinguish them. Based on the principle of radial basis function neural network, a neural network is obtained from the training of the 14 groups of experimental data. The results show that the species of sunset yellow and tartrazine could be recognized accurately. This method has potential applications in other synthetic food dyes detection and food safety inspection.

Phase-controlled gain, phase shift, and group velocity using a room-temperature active-Raman-gain medium

A four-level tripod active-Raman-gain scheme is analyzed for obtaining phase-controlled gain, phase shift, and group velocity at room temperature. The scheme can be used to eliminate significant probe field atten- uation or distortion which is unavoidable in the scheme based on electromagnetically induced transparency. It is shown that the intensity gain, phase shift, and group velocity of a probe field can be simultaneously manipulated by changing the relative phase of two pump fields. The scheme is also different from that proposed recently by Deng et al. where a probe-field gain always exists. New features of the scheme presented here raise the possibility of designing rapidly responding optical switches and gates for optical information processing.

Negative refraction and subwavelength imaging of a photonic-crystal slab for the frequencies in the third band

Negative refraction and subwavelength imaging properties of a two-dimensional （2D） photonic crystal （PC） slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directions of the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negative refractive-index material. The light radiated from a point source can form a subwavelength image spot through the PC slab. Negative refraction and an effective refractive index of the PC slab n = -1 can be achieved for the incident wave with its incident angle within a certain range.