Sulfur-capped cyclodextrins: a new class of cavitands with extroverted as well as introverted donor functionalities

Ansa-cyclodextrins were obtained in high yields by reaction of sodium sulfide with A,B-di- or A,B,D,E-tetramesylated alpha-CD precursors; the resulting thiocavitands are suitable for forming nanotubular molecules, as well as for hosting metal-organic fragments.     

Liquid-phase synthesis of polyhydroquinoline using task-specific ionic liquid technology

A new strategy for the synthesis of polyhydroquinolines from task-specific ionic liquids (TSIL) as a soluble support was developed. The preparation of the polyhydroquinolines by a three-component reaction was achieved by using ionic liquid-phase bound beta-oxo esters. These starting functionalized esters were synthesized by a solventless transesterification without catalyst under microwave irradiation. The structure of the intermediates in each step was verified routinely by spectroscopic analysis, and after oxidation of the polyhydroquinolines grafted on the TSIL with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone or after cleavage (transesterification, saponification-acidification), the target compounds were obtained in good yields and high purities.     

Cyclodextrin-based thiacavitands as building blocks for the construction of metallo-nanotubes

Two new cyclodextrin-based ligands with dual exo/endo binding domains were synthesised in high yields by reacting dimesylated or tetramesylated α-CD derivatives with sodium sulfide in either dimethylsulfoxyde or acetone/18-crown-6. The capping of adjacent glucose units was shown to be strongly favoured in both cases. Depending on the nature of the metal precursor being used, one of the synthesised thiacavitands forms either rigid nanotubular dimers or chelate complexes having receptor properties upon metal complexation.     

Thermal stability of P3HT and P3HT:PCBM blends in the molten state

The thermal stability of poly(3-hexylthiophene) (P3HT) in its molten state was investigated in air and nitrogen atmospheres under no illumination conditions, with the aim of testing the feasibility of processing it using polymer melt techniques. A large set of different experimental characterization techniques was used including thermogravimetric analysis (TGA), rotational rheometry, infrared spectroscopy (FTIR-ATR), proton nuclear magnetic resonance spectroscopy (¹H-NMR), gel permeation chromatography (GPC), UV-Vis and fluorescence spectroscopy. The results obtained strongly suggest that the processing of P3HT in its molten state is possible, without noticeable degradation, if carried out under nitrogen atmosphere and if the processing (residence) times are relatively short. Conversely, as expected, in a normal air atmosphere P3HT degrades rapidly at temperatures above its melting point. The effect of PCBM on the thermal stability of P3HT:PCBM blends in the molten state was also studied using TGA, and in air atmosphere PCBM is shown to delay oxidation.     

Transport of long neutral polymers in the semidilute regime through a protein nanopore

We investigate the entrance of single poly(ethylene glycol) chains into an α-hemolysin channel. We detect the frequency and duration of the current blockades induced by large neutral polymers, where chain radius is larger than pore diameter. In the semidilute regime, these chains pass only if the monomer concentration is larger than a well-defined threshold. Experiments are performed in a very large domain of concentration and molecular mass, up to 35% and 200 kDa, respectively, which was previously unexplored. The variation of the dwell time as a function of molecular mass shows that the chains are extracted from the semidilute solution in contact with the pore by a reptation mechanism.     

Direct Synthesis of Z,Boc, Fmoc,Alloc[ddot] Derivatives of 5-Aminooxazoles Starting from Acylamino Acids and Chlorosulfonylcarbamates

A one-step synthesis of 5-oxazolecarbamates 1–11 can be easily carried out starting from N-acetylated and benzoylated aminoacids such as Gly, Ala, Leu, Phe, and chlorosulfonyl carbamates, prepared in situ by addition of alcohols on chlorosulfonyl isocyanate (CSI). The structure of the compounds was confirmed by X-Ray crystallography. A subsequent exocyclic N-alkylation gave substituted 12–18 derivatives. Carbamate cleavage gave by spontaneous reopening substituted N-acylaminoamides, in excellent yields.     

Electroproduction of neutral pions at energies above the resonance region

The reaction e p→e'pπ⁰ has been measured at W=2.55 GeV a fixed electron scattering angle of 10.3°. Two magnetic spectrometers and a lead glass hodoscope were used to detect all four final state particles. Electroproduction cross sections in the t range ?0.15 to ?1.4 (GeV/c)² at q² = ?0.22, ?0.55 and ?0.85 (GeV/c)² are presented. Above |t|=0.6 (GeV/c)² the cross sections are considerably smaller than those for photoproduction.     

Rheological changes in the bitumen caused by heating and interaction with rubber during asphalt–rubber production

The demand for more safe and durable roads, combined with the need to preserve the environment, led to the production and application of asphalt–rubber (AR) on roads. Nevertheless, this complex material needs further study in order to better distinguish among the phenomena that take place during AR production, as they impact on the final product characteristics. Here, we effectively quantify the rheological changes related to bitumen aging due to diffusion of small molecules of bitumen into the rubber particles and to the release of fillers from rubber into the bitumen during AR production. “A sphere AR production simulator” was developed to assess AR aging independently. The comparison of the characteristic relaxation times of both AR and simulated AR shows that the aging alone cannot explain the rheological changes during AR production. The extent of the changes related to the combined effects of aging and filler release increases as the bitumen used to produce AR is softer.