Search

A fluorine-containing diamine, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (BAPPH) (II), was synthesized in two steps on condensation of 2,2-bis(4-hydroxyphenyl)hexafluoropropane with p-chloronitrobenzene in the presence of potassium carbonate, giving 2,2-bis[4-(4-nitrophenoxy)phenyl]hexafluoropropane (I), followed by reduction with hydrazine monohydrate/Pd—C. Fluorine-containing polyamides and copolyamides having inherent viscosities 0.41–0.88 dL g−1 were prepared by direct polycondensation of BAPPH with various aromatic diacids or with mixed diacids, by triphenyl phosphite and pyridine in N-methyl-2-pyrrolidinone (NMP). The polyamides were examined by elemental analysis, IR spectra, inherent viscosity, x-ray diffraction, solubility, DSC, and TGA. The diffractogram showed that the polyamides were crystalline except IVb, IVc, IVf, and Vc. Almost all polyamides were soluble in polar aprotic solvents. The polymers obtained from BAPPH lost no mass below 350°C, with 10% loss of mass being recorded above 467°C in nitrogen. These aromatic polyamides had glass transition temperatures in the 221–253°C range. © 1996 John Wiley & Sons, Inc.

Salicylate hydroxylase (SHL) catalyzes the production of catechol (plus CO(2) and H(2)O) from salicylate, NADH, and O(2). Coimmobilization of SHL with a NAD(P)(+)-dependent dehydrogenase in front of a Clark-type oxygen electrode has been investigated in the development of a general type of dehydrogenase-based biosensors that can detect various biological analytes; however, currently, no fluorophores are available for these applications. We synthesized the first new long-wavelength latent fluorogenic substrate SHLF (3) for SHL. In the presence of NADH and under aerobic conditions, SHL catalyzes the decarboxylative hydroxylation of SHLF followed by a quinone-methide-type rearrangement reaction concomitant with the ejection of a fluorescence coumarin 2, which is spontaneous and irreversible at physiological temperatures in aqueous media. The fluorescence signal generated by this process is specific and, in the near red spectral region with an emission maximum at 595 nm, is suppressed by salicylic acid. The fluorescence response of SHLF is insensitive to various biological reactive oxygen species (ROS) and reductants. Furthermore, SHLF is a sensitive fluorimetric indicator for analyte determination in the SHL-coupled dehydrogenase assay in which NAD(+) is converted to NADH. This novel fluorescence assay detected 3-hydroxybutyrate and cholesterol in the nanomolar range and is more sensitive than the current SHL-dehydrogenase amperometric sensors, making it applicable to the construction of a fiber-optic fluorescence biosensor for clinical diagnostic uses.

We synthesized a new long-wavelength latent fluorimetric probe BCC ( 6 ) to detect physiologically significant thiols. The fluorogenic chemical transformation of BCC triggered by thiols is through a tandem reaction, thiol-induced benzoquinone reduction, and quinone–methide-type rearrangement reaction, which are spontaneous and irreversible at physiological temperature in aqueous media. The fluorescence signal revealed by this process is specific and exhibited in the near-red spectrum region with emission maxima at 595 nm, and it could be competitively inhibited by thiols scavenger, N -ethylmaleimide. The fluorescent response of BCC is insensitive to various non-thiol amino acids and biological reductants. This novel fluorimetric probe demonstrates a good relationship in detecting thiols in 1–100 μM range, which presents to the applicability for the construction of fiber-optic biosensors in the future clinical diagnostic.

We synthesized a new long-wavelength latent fluorogenic probe BQC ( 1 ) to monitor DTD activity. The fluorogenic chemical transformation of BQC triggered by DTD in the presence of NADH is through a series of tandem reactions, DTD-catalyzed benzoquinone reduction, trimethyl-locks cyclization and intramolecular urea formation, which are spontaneous and irreversible at physiological temperature in aqueous media. The fluorescence signal revealed by this process is specific and exhibited in the near red spectrum region with emission maxima at 595 nm, and it could be competitively inhibited by menadione. The fluorescent response of BQC is insensitive to various biological thiol reductants. Furthermore, pro-fluorophore BQC is a sensitive fluorimetric indicator for analytes determination in the oxygen-insensitive DTD-coupled dehydrogenases assay by including NAD + which will convert to NADH by reaction in the presence of analytes. This novel oxygen-insensitive assay demonstrates a good relationship in detecting 3-hydroxybutyrate and glucose-1-phosphate in 1–10 μM range, which presents to the applicability for the construction of fiber-optic biosensors in the future clinical diagnostic.

Two novel near-infrared (NIR) electrochromic polynorbornenes, poly(NBDTPA) and poly(HNBDTPA), containing electroactive chromophores, were prepared via ring-opening metathesis polymerisation from a new norbornene derivative (NBDTPA) using Grubbs' catalysts followed by hydrogen reduction. The glass transition temperatures (Tg) of poly(NBDTPA) and hydrogenated poly(HNBDTPA) were 141 °C and 91 °C, respectively. The 10% weight-loss temperatures of hydrogenated poly(HNBDTPA) and poly(NBDTPA) were up to 440 °C and 397 °C, respectively. Hydrogenated poly(HNBDTPA) film showed excellent transparency (up to 91%). Poly(NBDTPA) showed a cyclic voltammogram and electrochromic behaviour that was similar to poly(HNBDTPA). The cyclic voltammogram of a poly(HNBDTPA) film cast onto an indium-tin oxide (ITO)-coated glass substrate exhibited three reversible oxidation redox couples at 0.63, 0.82 and 1.23 V vs. Ag/Ag+ in acetonitrile solution. The electrochromic characteristics of poly(HNBDTPA) showed excellent stability and reversibility, with multi-stage colour changes from its colourless neutral form to green, light-blue and dark-blue with applied potentials of 0 to 1.75 V. The colour switching time and bleaching time of the poly(HNBDTPA) were 7.1 s and 4.2 s in the near-infrared region (1230 nm), and 7.4 s and 4.5 s in the UV-vis region (420 nm), respectively.

A solution-processable functional polyimide (PYTPA-PI), containing triphenylamine-substituted diphenylpyridine moieties (PYTPA, electron donors) and phthalimide moieties (PI, electron acceptors), was synthesized. The copolymer exhibits a high glass transition temperature of 342 °C. A switching device, based on a solution-cast thin film of PYTPA-PI sandwiched between an indium-tin oxide (ITO) bottom electrode and an Al top electrode, exhibits two accessible conductivity states and can be switched from the low-conductivity (OFF) state to the high-conductivity (ON) state, with an ON/OFF current ratio of more than 103, at the threshold voltage of about 2.7 V. The ON state is volatile and relaxes readily to the OFF state. However, it can be electrically sustained by a refreshing voltage pulse of 2 V. The ON state can also be reset to the initial OFF state by a reverse bias of −0.9 V. The ability to write, erase, read, and refresh the electrical states fulfills the functionality of a dynamic random access memor...

Magnetic properties of cobalt films grown on Ge(111) and Si(111) substrates were investigated. On a Ge(111) substrate, cobalt films possess an in-plane anisotropy. On a Si(111) substrate, ultrathin cobalt films (3–9 monolayers), which were deposited at 300 K, exhibited a canted easy axis. The different orientations of the easy axis of magnetizations are attributed to the different roughness of the film/substrate interfaces. Interaction between Co layers and the substrates produces intermixed compound layers that are nonmagnetic. The thickness of this compound layer is 3.8 monolayers for Co/Ge(111), and 2.1 monolayers for Co/Si(111). A series of annealing experiments showed that the onset temperature of the disappearance of the magnetism for Co films is lower on Ge than that on Si substrate. For cobalt film, this onset temperature is 300 K on Ge(111) and 575 K on Si(111).