RESUMO
Four novel isoindigo-thiophene D-A-D-type precursors are synthesized by Stille coupling and electrosynthesized to yield corresponding hybrid polymers with favorable electrochemical and electrochromic performances. Intrinsic structure-property relationships of precursors and corresponding polymers, including surface morphology, band gaps, electrochemical properties, and electrochromic behaviors, are systematically investigated. The resultant isoindigo-thiophene D-A-D-type polymer combines the merits of isoindigo and polythiophene, including the excellent stability of isoindigo-based polymers and the extraordinary electrochromic stability of polythiophene. The low onset oxidation potential of precursors ranges from 1.10 to 1.15 V vs. Ag/AgCl, contributing to the electrodeposition of high-quality polymer films. Further kinetic studies illustrate that isoindigo-thiophene D-A-D-type polymers possess favorable electrochromic performances, including high optical contrast (53%, 1000 nm), fast switching time (0.8 s), and high coloration efficiency (124 cm2 C-1). These features of isoindigo-thiophene D-A-D-type conjugated polymers could provide a possibility for rational design and application as electrochromic materials.
Assuntos
Polímeros , Tiofenos , CinéticaRESUMO
Owing to the lack of research on structure-activity relationship and interaction mechanism between unsaturated polyester resins (UPR) and flame retardants, it has been a big challenge to prepare high-efficiency flame retardants for UPR in industry. In this research, to explore structural rules of high-efficiency flame retardants, several polymeric flame retardants were synthesized with varied main-chain, side-chain, phosphorus valence states and contents of flame retardant elements. The thermal stabilities of flame retardants and UPR composites were firstly assessed. It has been found the interaction existed between flame retardants and UPR, through transesterification reaction and ß scission pathway in polyester and polystyrene chains. With only 15â¯wt% of PCH3-S, UPR composites can reach V0 rating in UL-94. The PHRR and THR values can be maximumly decreased by 71.66 % and 77.67 %, with 20â¯wt% of PB-S. It has been found flame retardants with sulfone group andâ¯+â¯3 valence state of phosphorus in molecular backbone can release SO2 and phosphorus containing compounds in gaseous phase, which diluted fuel fragments and catalyzed Hâ and HOâ radical removal. The mechanism for improved flame retardancy of UPR composites with various polymeric flame retardants were discussed in detail. Some general rules for highly efficient flame retardant UPR can be summarized: First, gaseous phase flame retardant mechanism plays the major role in improvement of flame retardant performance of UPR composites; Second, the combination ofâ¯+â¯3 valence state of phosphorus structures, higher phosphorus contents and sulfone groups effectively improves the flame retardant efficiency of flame retardants.
Assuntos
Retardadores de Chama , Fósforo , Poliésteres , PolímerosRESUMO
Developing selective and sensitive methods for tertiary butylhydroquinone (TBHQ) detection is of great significance to ensure the quality and safety of food. Herein, an electrochemical sensor was designed for selective and sensitive detection of TBHQ by integrating molecularly imprinted polymer, noble metal nanoparticles and carbon materials. The electrochemical sensor exhibited excellent performance for sensitive determination of TBHQ. The linear range was 0.5-60⯵gâ¯mL-1 with a low detection limit of 0.046⯵gâ¯mL-1. In addition, the results obtained by electrochemical method were well agreement with the detection results obtained by HPLC with good recoveries ranging from 99.4 to 108.5% in spiked edible oil samples. The present study not only has theoretical value to establish new methods for rapid detection of food additives but also has potential application values for monitoring the overuse of TBHQ.