This paper discusses a new family of ferroelectric polymorphic fluoroterpolymers comprosed of vinylidene difluoride (VDF), trifluoroethylene (TrFE), and a chloro-containing third monomer, such as chlorodifluoroethylene (CDFE), and chlorotrifluoroethylene (CTFE), which feature relatively narrow molecular weight and composition distributions. The terpolymers were prepared by a bulk reaction process with a low temperature free radical initiator, i.e., the oxidation adducts of trialkylborane and oxygen. The slightly bulky chlorine atom serves as a kink in the polymer chain, which spontaneously alters the chain conformation and crystalline structure. Compared to the corresponding VDF/TrFE copolymer (>20 mol % of TrFE), the slowly increasing chlorine content (<8 mol % of termonomer) gradually changes the all-trans (t m >4) chain conformation (β-phase) to tttg+tttg- conformation (γ-phase) without significant reduction of overall crystallinity. The Curie (ferroelectric−paraelectric) phase transition temperature between the mixed ferroelectric β- and γ-phases and paraelectric α-phase (tg+tg- conformation) also gradually reduced to near ambient temperature with very small activation energy. Consequently, the terpolymers show high dielectric constant (>70), slim polarization hysteresis, and large electrostrictive response (>4%) at ambient temperature and exhibit common ferroelectric relaxor behaviors with a broad dielectric peak that shifted toward higher temperatures as the frequency increased.

Terpolymers of vinylidene fluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE) were synthesized as potential materials for electromechanical transduction. These terpolymers had relatively high molecular weights (∼30 kg/mol) and CTFE levels in the range of 5−10 mol %. The presence of the bulky CTFE units disrupts the sequence length of the crystal, which lowers both the melting and Curie transitions; however, the degree of crystallinity remains high. The formation of smaller, more mobile polar domains gives rise to good electromechanical response. At low electric fields (7 MV/m), longitudinal strains as high as 0.5% are attained. This is significantly higher than the strains achieved with the same terpolymer obtained by bulk polymerization. The present materials exhibit a low mechanical modulus (ca. 0.2 GPa) relative to other VDF−TrFE copolymers. This might limit their use, depending on the application.

This paper discusses a new ferroelectric polymer with large electrostrictive response (-4%) at ambient temperature, which is based on a processable semicrystalline terpolymer comprising vinylidene difluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE). This VDFITrFEICTFE terpolymer was prepared by a combination of bulk polymerization process and a borane/oxygen initiator at ambient temperature. The incorporated bulky CTFE units in the terpolymer seem to reduce the crystalline domain size and move the ferroelectric-paraelectric (F-P) phase transition to near ambient temperature with a very small energy barrier. Some terpolymers exhibited common ferroelectric relaxor behaviors with a broad dielectric peak that shifted toward higher temperatures as the frequency increased, and a slim polarization hysteresis loop at near the dielectric peak (around ambient temperature) that gradually evolved into a normal ferroelectric polarization hysteresis loop with reduced temperature.

Immobilization methods have emerged as feasible solutions for increasing the re-usability of biocatalysts, and for simplifying their separation from the desired products. Immobilized biocatalysts can directly be applied to a...

The mechanism underlying the large electric-field-induced strains in terpolymers of vinylidene fluoride, trifluoroethylene, and chlorotrifluoroethylene was investigated. The electrostrictive strain increased by an order of magnitude with increasing temperature, up to the Curie transition, and was essentially invariant to temperature thereafter. Infrared absorption spectra, obtained as a function of both temperature and electric field strength, revealed no change in the crystal phase structure for electric fields sufficient to induce longitudinal strains of ∼1%. Thus, the electrostriction observed herein is not due to crystal phase conversion. The Maxwell strain was also negligible under all conditions, because of the terpolymer’s high mechanical modulus (10 to 100 MPa). The mechanical properties exhibit an anomalous change in behavior near the Curie transition, whose origin is unclear.

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Lactic acid/ethylene terephthalate copolyesters were synthesized by the standard melt polycondensation of lactic acid (L), ethylene glycol (EG) and dimethyl-terephthalate (DMT). Effects of reaction temperatures and types of catalysts on the structures and properties of the copolymers were examined. In addition, feasibility of promoting the copolymerization process by a novel synthesis step of using thermo-stabilizers was investigated. The results show that a reaction temperature of higher than 180°C is necessary to produce copolymers with appreciable molecular weight. However, degradation was observed when the reaction temperature is higher than 220°C. Triphenyl phosphate (TPP) shows promising results as a potential thermo-stabilizer to minimize this problem. It was found that Sb2O3 and Tin(II) octoate are most effective among 4 types of catalysts employed in this study. 1H-NMR results indicate that copolymers have a random microstructure composed mainly of single L units alternately linked with ET blocks at various sequential lengths. The longer ET sequence in the chain structure leads to the increase in melting temperature of the copolymer. TGA results show that the resulting copolymers possessed greater thermal stability than commercially-available aliphatic PLA, as a result of the inclusion of T (terephthalate) units in the chain structure

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