Microphase-separated structures of diblock copolymers with narrow molecular weight distributions but with various composition distributions were investigated. Monodisperse nine parent block copolymers composed of polystyrene and poly(2-vinylpyridine) having almost the same molecular weight but with different polystyrene volume fraction, φs, covering 0.1-0.9, were prepared. Successively they were blended variously to produce samples with various composition distributions but with constant average composition; that is, φ s was kept constant at approximately 0.5. Structures from solvent-cast and well-annealed films were observed through transmission electron microscopy and small-angle X-ray scattering. It has been found that the blends with wide composition distributions show periodic alternating lamellar structure up to 1.7 in terms of M w(S)/Mn(S), where Mw(S) and Mn(S) denote weight-average and number-average molecular weights of polystyrene block, respectively, and that the microdomain spacing increases with increase of polydispersity of each block. Further, it was clarified that the blend shows macrophase separation in between two kinds of regular microphase-separated structures if M w(S)/ Mn(S) reaches approximately 1.8.

Thermal decomposition behaviors of a series of imidazolium-type ionic liquid samples were studied by pyrolysis-gas chromatography at 550˚C using various detectors. As for the imidazolium halides, haloalkanes and 1-alkylimidazoles corresponding to the alkyl substituents were mainly formed through the nucleophilic attacks of halide ions to the alkyl groups followed by C-N bond cleavage, along with a minor amount of alkenes. Meanwhile, in the case of the ionic liquids with BF4, PF6 and CF3SO3 anions, corresponding alkenes were predominantly produced along with 1-alkylimidazoles rather than haloalkanes. No boron-containing products were found even from the samples with BF4 anion, whereas minor but clear peaks of phosphorous-containing products were observed in the pyrograms of the samples with PF6 anions. As for the samples with longer alkyl group, the pyrolyzates reflecting the C-C bond scissions in the alkyl groups were also formed to some extent. Meanwhile, imidazole rings did not decompose under the experimental conditions at around 550˚C.

No abstract

No abstract

The reactive pyrolysis-gas chromatography technique was applied to verify the branching and/or cross-linking structures in an industrially available PC sample and its thermally treated ones through identification of specific pyrolysis products directly reflecting the related abnormal structures. On the pyrograms of the thermally treated samples, the peaks reflecting the abnormal structures such as branching and/or cross-linking were observed together with those reflecting main chain and end groups. Although the formations of these branching and/or cross-linking structures during the thermal treatment of PC had been suggested early, the identification of these pyrolysis compounds by reactive pyrolysis verified the existence of these structures. Furthermore, the fact that some of those characteristic peaks were also observed on the pyrogram of the industrially available PC sample prepared by the melt method indicated that the branching and/or cross-linking reactions would occur to some extent in the industrial polymerization reactor to synthesize the PC by the melt method.

A method to determine chemical composition of natural resin shellac was developed on the basis of reactive pyrolysis-gas chromatography (Py-GC) in the presence of an organic alkali, tetramethylammonium hydroxide ((CH(3))(4)NOH, TMAH). Py-GC using 25% TMAH aqueous solution enabled the highly sensitive determination of terpenic acids, aleuritic acid, several minor fatty acids, and the wax components of shellac as their methyl derivatives on the resulting pyrograms with less than 2.0% relative standard deviations without using any cumbersome pretreatment. The observed average distributions of each resin acid component determined by reactive Py-GC for shellac samples from India and Thailand showed that the average ratios among terpenic acids, aleuritic acid, and the other fatty acids were about 53:34:14 for Indian shellac and 51:35:14 for Thailand shellac, respectively, suggesting a slightly significant difference. However, clearer discrimination of the shellac samples from the two different growing places was attainable by applying principal component analysis for the mole percent distributions of all the acidic components determined by reactive Py-GC.

A new method to determine directly and rapidly the degree of acetylation of chitin/chitosan was developed based on reactive pyrolysis-gas chromatography in the presence of an oxalic acid aqueous solution. The degree of acetylation was precisely evaluated on the basis of peak intensities of the characteristic products such as acetonitrile, acetic acid, and acetamide originating from the N-acetyl group of N-acetyl-d-glucosamine units of chitin/chitosan. The observed values were in good agreement with those obtained by (1)H NMR and the other methods. Moreover, the proposed technique was applicable to any kinds of chitin/chitosan samples over the whole range of acetylation including insoluble chitin/chitosan and perfectly acetylated artificial chitin having higher crystallinity to which (1)H NMR had been inapplicable.

No abstract