Equilibrium anionic polymerization of 4,7-dioxaoctanal and n-octanal

Equilibrium anionic polymerization of 4,7-dioxaoctanal (DOA) and n-octanal (OA) was carried out in tetrahydrofuran in the temperature range of ?90 to ?68°C, and thermodynamic parameters were evaluated as follows: ΔH_ss = ?4.0 ± 0.1 kcal/mole, ΔS_ss = ?18.4 ± 0.5 cal/mole-deg, and T_c,ss = ?56°C for the DOA system; ΔH_sc = ?3.4 ± 0.1 kcal/mole, ΔS_sc = ?15.7 ± 0.4 cal/mole-deg, and T_c,sc = ?59°C for the OA system. Comparison of these values with those in the cases of β-methoxypropionaldehyde and n-valeraldehyde made it clear that the aliphatic aldehyde having a longer alkyl group polymerizes with smaller changes of enthalpy and entropy and that the polar-substituted aldehydes have higher polymerizability than the corresponding unsubstituted aliphatic aldehydes in the temperature range studied. These effects of substituents are interpreted from the viewpoint of the intermolecular interactions of polar groups in monomers and their polymers.     

Photoreactive fluorinated polyimide protected by a tetrahydropyranyl group (THP) based on photo-induced acidolysis

A polyimide (6F-THP) with a tetrahydropyranyl group (THP) in its side chain has been synthesized. The THP group exhibits a high acidolysis rate in this polymer's film. This rate was faster than that of a tertbutoxycarbonyl group (t-BOC), which has been previously reported [1]. Furthermore, the deprotected fluorinated polyimide (6FDA-AHHFP) became soluble in an aqueous base due to the presence of a hydroxyl group attached to the phenyl group of the diamine segment. The polyimide thus provides high performance as a photopolymer when used in conjunction with a photoacid generator after the post-exposure baking process (PEB). The photoacid generators used in this study were p-nitrobenzyl-9,10-dimethoxyanthoracene-2-sulfonate (NBAS) and diphenyliodonium-9,10-dimethoxyanthoracene-2-sulfonate (DIAS). The quantum yields of photodissociation and photoacid generation were also measured. The photoacid-generating quantum yields closely corresponded to the photosensitivities of the photoreactive polyimide system. It was confirmed that the THP group was easily deprotected even in the 6F-THP film with p-toluenesulfonic acid as a model acid catalyst. The activation energy of the THP deprotection reaction was determined to be 12.8 kcal/mol (19.5 kcal/mol in the case of t-BOC). The relationships between the THP deprotecting rate constant (k_d) and acid molecular size and between k_d and polyimide structure were further investigated.     

Polymer-nanoparticle complexes: from dilute solution to solid state

We report on the formation and the structural properties of "supermicellar" aggregates made from mineral nanoparticles and polyelectrolyte-neutral block copolymers in aqueous solutions. The mineral particles put under scrutiny are ultrafine and positively charged yttrium hydroxyacetate nanoparticles. Combining light, neutron, and X-ray scattering experiments, we have characterized the sizes and the aggregation numbers of the organic-inorganic complexes. We have found that the hybrid aggregates have typical sizes in the range of 100 nm and exhibit a remarkable colloidal stability with respect to ionic strength and concentration variations. Solid films with thicknesses up to several hundreds of micrometers were cast from solutions, resulting in a bulk polymer matrix in which nanoparticle clusters are dispersed and immobilized. It was found in addition that the structure of the complexes remains practically unchanged during film casting.     

Nickel-catalysed bis-allylation of internal alkynes with triallylindium

The Ni-catalysed reaction of triallylindium with internal alkynes underwent bis-allylation to afford octa-1,4,7-trienes in high yield.     

Channeled spectropolarimetry using a coherent white-light continuum

We carry out polarization measurements using a coherent white-light continuum as a light source for channeled spectropolarimetry. The white-light continuum, whose spectrum ranges from the UV to the IR region, is generated in Kr gas by a terawatt femtosecond laser system. The complete set of Stokes parameters from 450-700 nm are reconstructed from one spectral measurement. Also, the effectiveness of channeled spectropolarimetry using a coherent white-light continuum is experimentally demonstrated with a highly attenuating sample whose transmittance is as low as 10(-6).     

Growth of b-axis oriented VO2 thin films on glass substrates using ZnO buffer layer

VO₂ thin films are grown on glass substrates by pulsed laser deposition using vanadium metal as a target. In this study, a ZnO thin film was used as a buffer layer for the growth of VO₂ thin films on glass substrates. X-ray diffraction studies showed that the VO₂ thin film had b-axis preferential orientation on a c-axis oriented ZnO buffer layer. The thickness of the ZnO buffer layer and the oxygen pressure during VO₂ deposition were optimized to grow highly b-axis oriented VO₂ thin films. The metal-insulator transition properties of the VO₂ film samples were investigated in terms of infrared reflectance and electrical resistance with varying temperatures.     

Infrared multiphoton dissociation spectroscopic analysis of peptides and oligosaccharides by using fourier transform ion cyclotron resonance mass spectrometry with a midinfrared free-electron laser

The fragmentation of peptides and oligosaccharides in the gas phase was investigated by means of electrospray ionization Fourier transform ion cyclotron resonance (FTICR) mass spectrometry coupled with dissociation by a laser-cleavage infrared multiphoton dissociation (IRMPD) technique. In this technique, an IR free-electron laser is used as a tunable source of IR radiation to cause cleavage of the ionized samples introduced into the FTICR cell. The gas-phase IRMPD spectra of protonated peptides (substance P and angiotensin II) and two sodiated oligosaccharides (sialyl Lewis X and lacto-N-fucopentaose III) were obtained over the IR scan range of 5.7-9.5 microm. In the IRMPD spectra for the peptide, fragment ions are observed as y/b-type fragment ions in the range 5.7-7.5 microm, corresponding to cleavage of the backbone of the parent amino acid sequence, whereas the spectra of the oligosaccharides have major peaks in the range 8.4-9.5 microm, corresponding to photoproducts of the B/Y type.