Quick water-responsive shape memory hybrids with cellulose nanofibers

A type of quick water-responsive shape memory hybrids is fabricated by introducing cellulose nanofibrous mats as the filler in a polymeric matrix. Cellulose nanofibrous mats are obtained through hydrolyzing electrospun cellulose acetate (CA) nanofibers, then casted in thermoplastic polyurethane (TPU) solution to form the hybrids. The quick shape memory behavior of the formed hybrids is demonstrated using dynamic mechanical analysis (DMA) and stress–strain cyclic test. According to a predetermined protocol, the hybrids present desirable shape fixation and recovery, and the elastic modulus (E′) is shown to be responsive promptly and reversibly against drying and wetting cycle. Shape memory mechanism of the hybrids involves the reversible and competitive hydrogen bonds within cellulose before and after water immersion as well as the entropy elasticity of the TPU matrix. This study can pave a way to design novel smart materials by facile methods through incorporating natural nanomaterials as water sensitive fillers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 767–775     

Expedited Synthesis of Benzofuran-2-Carboxylic Acids via Microwave-Assisted Perkin Rearrangement Reaction

3-Halocoumarins are readily converted into benzofuran-2-carboxylic acids via a Perkin (coumarin-benzofuran ring contraction) rearrangement reaction. This rearrangement entails initial base catalyzed ring fission. The resulting phenoxide anion then attacks a vinyl halide to produce the final benzofuran moiety. We explored this reaction under microwave reaction conditions and were able to significantly reduce reaction times as well as obtain very high yields of a series of benzofuran-2-carboxylic acid derivatives.     

Development of a rapid method for the quantitative determination of deoxynivalenol using Quenchbody

Quenchbody (Q-body) is a novel fluorescent biosensor based on the antigen-dependent removal of a quenching effect on a fluorophore attached to antibody domains. In order to develop a method using Q-body for the quantitative determination of deoxynivalenol (DON), a trichothecene mycotoxin produced by some Fusarium species, anti-DON Q-body was synthesized from the sequence information of a monoclonal antibody specific to DON. When the purified anti-DON Q-body was mixed with DON, a dose-dependent increase in the fluorescence intensity was observed and the detection range was between 0.0003 and 3 mg L⁻¹. The coefficients of variation were 7.9% at 0.003 mg L⁻¹, 5.0% at 0.03 mg L⁻¹ and 13.7% at 0.3 mg L⁻¹, respectively. The limit of detection was 0.006 mg L⁻¹ for DON in wheat. The Q-body showed an antigen-dependent fluorescence enhancement even in the presence of wheat extracts. To validate the analytical method using Q-body, a spike-and-recovery experiment was performed using four spiked wheat samples. The recoveries were in the range of 94.9–100.2%. The concentrations of DON in twenty-one naturally contaminated wheat samples were quantitated by the Q-body method, LC-MS/MS and an immunochromatographic assay kit. The LC-MS/MS analysis showed that the levels of DON contamination in the samples were between 0.001 and 2.68 mg kg⁻¹. The concentrations of DON quantitated by LC-MS/MS were more strongly correlated with those using the Q-body method (R² = 0.9760) than the immunochromatographic assay kit (R² = 0.8824). These data indicate that the Q-body system for the determination of DON in wheat samples was successfully developed and Q-body is expected to have a range of applications in the field of food safety.     

Thermotropic liquid crystalline polymers containing five-membered heterocyclic groups VIII. Synthesis, and liquid crystalline and photoluminescent properties of semi-rigid polyesters based on a distyrylbenzene analogue of 1,3,4-thiadiazole

New semi-rigid polyesters composed of the distyrylbenzene analogue of 1,3,4-thiadiazole, 2,5-bis(2-phenylethenyl)-1,3,4-thiadiazole and aliphatic (dodeca-, deca- and octamethylene) chains were prepared by high temperature solution polycondensation; their liquid crystalline (LC) and photoluminescent properties were investigated. Differential scanning calorimetry, polarizing microscopy and powder X-ray diffraction show that the polyesters having both dodeca- and decamethylene chains form a thermotropic smectic C phase and a lyotropic LC phase in trifluoroacetic acid, but the polyester containing octamethylene chains only exhibits a thermotropic smectic C phase. Solution and solid state absorption and fluorescent spectra indicate that all the polyesters in this work display absorption maxima based on the 2,5-bis(2-phenylethenyl)-1,3,4-thiadiazole moiety, emitting blue light in HFIP solutions and bluish-green light in solids; the Stokes shifts are 80.1-80.7 nm in solution and 74.2-87.2 nm in the solid state.     

X-ray microscopy studies of protein adsorption on a phase-segregated polystyrene/polymethyl methacrylate surface. 1. Concentration and exposure-time dependence for albumin adsorption

X-ray photoemission electron microscopy using synchrotron radiation illumination has been used to measure the spatial distributions of albumin on a phase-segregated polystyrene/poly(methyl methacrylate) (PS/PMMA) polymer thin film following adsorption from unbuffered, deionized aqueous solutions under a range of solution concentrations and exposure times. Chemical mapping of the albumin, PS, and PMMA shows that the distribution of albumin on different adsorption sites (PS, PMMA, and the interface between the PS and PMMA domains) changes depending on the concentration of the albumin solution and the exposure time. The preferred sites of absorption at low concentration and short exposure are the PS/PMMA interfaces. Albumin shows a stronger preference for the PS domains than the PMMA domains. The exposure-time dependence suggests that a dynamic equilibrium between albumin in solution and adsorbed on PS domains is established in a shorter time than is required for equilibrating albumin between the solution and the PMMA domains. The explanation of these preferences in terms of possible adsorption mechanisms is discussed.     

Synthesis of potent and selective inhibitors against the proliferation of human coronary artery smooth muscle cells

A series of diarylamide urea derivatives were synthesized and evaluated for their inhibitory activities against human coronary artery smooth muscle cells (SMCs) and human coronary artery endothelial cells (ECs). Compound 2h was much superior to Tranilast, in terms of both the potency of its inhibitory activity toward the proliferation of SMCs and the cell selectivity.     

Forensic discrimination of photocopy and printer toners II. Discriminant analysis applied to infrared reflection-absorption spectroscopy

Copy toner samples were analyzed using reflection-absorption infrared microscopy (R-A IR). The grouping of copy toners into distinguishable classes achieved by visual comparison and computer-assisted spectral matching was compared to that achieved by multivariate discriminant analysis. For a data set containing spectra of 430 copy toners, 90% (388/430) of the spectra were initially correctly grouped into the classifications previously established by spectral matching. Three groups of samples that did not classify well contained too few samples to allow reliable classification. Samples from two other pairs of groups were similar and often misclassified. Closer examination of spectra from these groups revealed discriminating features that could be used in separate discriminant analyses to improve classification. For one pair of groups, the classification accuracy improved to 91% (81/89) and 97% (28/29), for the two groups, respectively. The other pair of groups were completely distinguishable from one another. With these additional tests, multivariate discriminant analysis correctly classified 96% of the 430 R-A IR toner spectra into the toner groups found previously by spectral matching.This is publication number 03–03 of the Laboratory Division of the Federal Bureau of Investigation. Names of commercial manufacturers are provided for identification only, and inclusion does not imply endorsement by the Federal Bureau of Investigation.     

Halogen-substituent effect on the spectroscopic properties of 2-phenyl-6-dimethylaminobenzothiazoles

6-Dimethylamino-2-phenylbenzothiazole (1-H) is a push-pull benzothiazole fluorophore mimicking the firefly oxyluciferin structure. We newly prepared 7-chloro and 7-bromo derivatives of 1-H and its 4-acetyl derivative (2-H), and their spectroscopic and photophysical properties were investigated. The halogenated derivatives showed the blue-shifted electronic absorption maxima and fluorescence emission maxima compared to 1-H and 2-H, resulted from the deformations of the NMe₂ groups and the electron withdrawing properties of the halogen groups. In addition, the halogen substitutions accelerate intersystem crossing by heavy atom effect, resulting in a decrease in fluorescence quantum yields. Interestingly, however, the halogenated derivatives of 2-H still showed moderate fluorescence quantum yields. The halogenation effect is one of the guides to design push-pull benzothiazole fluorophores for tuning fluorescence properties.     

Forensic discrimination of photocopy and printer toners I. The development of an infrared spectral library

Microscopical reflection-absorption by infrared spectroscopy (R-A IR) was shown as a viable technique for analyzing the polymer resins contained in dry, black photocopy and printer toners. The sampling technique involves a heat transfer of the toner from a document to the reflective surface of aluminum foil followed by analysis by R-A IR. The technique is simple, fast, and readily available to most forensic laboratories. A searchable spectral library was created that contains 807 toner samples analyzed by R-A IR. Ninety-eight groups were established based on spectral characteristics, and a flowchart was developed to assist with group assignments. A blind study was conducted to compare twenty photocopied documents each paired to a test document to determine if the pair could have been produced from the same copier. The analyst obtained 100% correct results in this study. Tests on thirty samples with the spectral library produced 90% first hits for the correct group. The three remaining samples were correctly determined by visual comparison of spectra for the top three hits. An actual case study was conducted where the investigation was narrowed from 400 possible machines to eight based on a comparative study of the photocopy toners.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00216-003-2073-0This is publication number 03-02 of the Laboratory Division of the Federal Bureau of Investigation. Names of commercial manufacturers are provided for identification only and inclusion does not imply endorsement by the Federal Bureau of Investigation. This paper was presented in part as a poster at the International Symposium on the Forensic Examination of Trace Evidence in Transition, San Antonio, Texas, 24–28 June 1996.     

Radical cation salts induced domino reaction of anilines with enol ethers:Synthesis of 1,2,3,4-tetrahydroquinoline derivatives

A domino reaction of anilines with cyclic and acyclic enol ethers induced by catalytic amounts of TBPA^·+（5 mol%） was investigated and a series of 2,4-disubstituted-1,2,3,4-tetrahydroquinolines were synthesized.Different from cyclic enol ethers, when acyclic enol ethers were used in the reaction,they serve as surrogates of acetaldehyde,producing a series of 2-methyl-4- anilino-1,2,3,4-tetrahydroquinolines.A single electron transfer mechanism was proposed to rationalize the products formation.