The Structure−Property Relationship of Poly(vinylidene difluoride)-Based Polymers with Energy Storage and Loss under Applied Electric Fields

This paper systematically examines the family of poly(vinylidene difluoride) (PVDF)-based fluoropolymers, including homo-, co-, and terpolymers containing vinylidene fluoride (VDF), trifluorethylene (TrFE), and chlorotrifluoroethylene (CTFE) units, with the objective of tuning the polymer chain conformation and crystal structure in order to identify the most suitable polymer for energy storage (capacitor) applications. All polymers have high molecular weight, uniform composition distribution, semicrystallinity, and high purity. They were prepared by a borane/oxygen control radical initiator in a homogeneous solution at ambient temperature. The resulting polymers were solution-cased, then melt-conditioned into uniform (defect-free) thermoplastic thin films (thickness 10−20 μm). The combination of thermal, dielectric, and uni- and bipolar charge displacements reveals their polarization profiles, which are dependent on chain conformation, crystal phase, crystal size, Curie temperature, and ac and dc fields. Ferroelectric VDF/TrFE copolymers, having all-trans chain conformation and polar β-phase crystals, exhibiting huge remnant polarization, are not suitable for energy storage (capacitor) applications. Some poled PVDF homopolymer and VDF/CTFE copolymers with γ-phase crystals show potential for dc (not ac) powered applications. The most suitable polymer is the VDF/TrFE/CTFE terpolymer having a TTTG chain conformation, small polar γ-phase crystals, relaxed dielectric properties, and a Curie transition at near ambient temperature, providing both ac and dc powered capacitors with a balance of properties, high-energy density and low-energy loss

Study of VDF/TrFE/CTFE Terpolymers for High Pulsed Capacitor with High Energy Density and Low Energy Loss

Study of VDF/TrFE/CTFE Terpolymers for High Pulsed Capacitor with High Energy Density and Low Energy Los

Study of Chain Transfer Reaction to Solvents in the Initiation Stage of Atom Transfer Radical Polymerization

ATRP has been recognized as a powerful tool to synthesize polymers with well-defined structures, narrow polydispersity, and controlled molecular weight in the past decades. Usually, it is believed that the typical side reactions (such as termination and chain transfer reactions) in typical radical polymerizations could be inhibited in ATRP for the persistent radical effect. More recently, some researchers did notice that some chain transfer reaction to N containing ligands happens in ATRP. However, the chain transfer constant (ktr/kp) in ATRP has never been able to be measured experimentally due to the difficulty of determining the precise composition of the resultant polymer. Therefore, the influence of chain transfer reaction onto ATRP has rarely been discussed. In this work, we provide a novel method to determine the competition between chain transfer reaction and initiation reaction of free radicals (ktr/ki) by analyzing the structure of grafting copolymers from poly(vinylidene fluoride-co-trichlorofluoride ethylene) P(VDF-co-CTFE). The perfect coincidence of experimental results with theoretical ones indicates that the method may help to understand the chain transfer reaction in ATRP as well as its influence on the chain end of resultant polymer

Noise-like Pulses from an All-Normal-Dispersion Fiber Laser with Weakened Spectrum Filtering

Noise-like pulses (NLP) are extremely sought after in many fields. Here, we experimentally and numerically investigated the generation of noise-like pulses in an all-normal-dispersion fiber laser with weak spectrum filtering. With the insertion of the grating as a tunable spectrum filter, the laser operates at a stable dissipative soliton state with a 3.84 ps duration. Replacing the grating with a mirror, NLPs with double-scale intensity autocorrelation trace is ultimately attained. Numerical simulations are performed in detail and demonstrated that with the absence of a spectrum filter, the stable state cannot be established but form the random pulse cluster. The random pulse cluster achieves dynamic stability with suitable feedback, and the NLP is ultimately generated. The NLP here is directly evolved by the initial noise, and no other states occur during its evolution. These explorations could deepen the understanding of NLP and enrich the complex dynamics of the ANDi ultrafast fiber laser

Phylogenetic tree of 41 TTSuV2 sequences and 29 TTSuV1 sequences.

<p>● represents TTSuV2 and ○ represents TTSuV1.</p

Copper-Catalyzed Oxidative <i>ipso</i>-Annulation of Activated Alkynes with Silanes: An Approach to 3‑Silyl Azaspiro­[4,5]­trienones

A novel strategy of silylation and dearomatization of activated alkynes with silanes to synthesize azaspiro­[4,5]­trienones is developed, which could be facilely achieved through a tandem difunctionalization of alkyne, dearomatization, and oxidation and provided a facile approach to produce useful 3-silyl azaspiro­[4,5]­trienones in an efficient manner

Distribution of the ENC values and GC content at synonymous codon third position (GC_3S).

<p>The curve indicates the expected codon usage if compositional constraint alone account for codon usage bias.</p

Correspondence analysis of codon usage patterns of TTSuV2 and TTSuV1.

<p>Correspondence analysis of codon usage patterns of TTSuV2 and TTSuV1.</p

Cluster tree result of 41 TTSuV2 genes based on hierarchical cluster method.

<p>Cluster tree result of 41 TTSuV2 genes based on hierarchical cluster method.</p

Recombination analysis of TTSuV2 and TTSuV1 sequences using the RAT.

<p>The colour of the line on the graph is the same as the colour of its sequence name on the left.</p