Synthesis and characterization of stereoregular poly(methyl methacrylate)–silica hybrid utilizing stereocomplex formation

Stereoregular poly(methyl methacrylate) (PMMA)–silica nanocomposites were prepared using stereocomplex formation between i-PMMA and s-PMMA by an in situ method. The methodology adopted here is the simultaneous formation of organic gel and inorganic gel, the so-called interpenetrating polymer network (IPN) formation. The gelation of i- and s-PMMA were performed by stereocomplex formation with the associated segments forming the crosslinking points in the presence of tetramethoxysilane (TMOS). The effects of the i/s-ratio, PMMA concentration, molecular weight, and solvent nature on the hybrid materials formation were addressed. The presence of the stereocomplex in the silica matrix was confirmed by DSC and solvent extraction methods. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 785–794, 2004     

Effect of crystallization behavior of polyethylene glycol 6000 on the properties of granules prepared by fluidized hot-melt granulation (FHMG)

The objective of this study was to investigate the effect of the crystallization behavior of Macrogol 6000 (polyethylene glycol 6000; PEG 6000), used as a binder, during the solidification process on the properties of mononucleic granules prepared by the fluidized hot-melt granulation (FHMG) technique. Crystallization of PEG 6000 from molten liquid was investigated using differential scanning calorimetry (DSC) and hot stage microscopy. The results obtained from the measurement of isothermal crystallization demonstrated that crystallization of PEG 6000 was either slow or rapid. Analysis based on solid-state decomposition showed that slow crystallization was due to the two-dimensional growth of nuclei mechanism, while rapid crystallization was due to the three-dimensional growth of nuclei mechanism. Observation of the crystallization of PEG 6000 by hot stage microscopy supported the existence of two different crystallization mechanisms. Granules containing PEG 6000 that underwent rapid crystallization during FHMG showed a significantly higher fraction powder under 150 microm in diameter. This was caused by the loss of powder particles from the surface of mononucleic granules during the solidification process, because many cracks were observed after crystallization of PEG 6000 with a short isothermal crystallization time (ICT) due to the reduced of sticking of particles. The results of this study suggested that the crystallization behavior of the binder during the solidification process of FHMG can influence the properties of the resultant granules, such as particle size distribution, content uniformity or taste masking. It was also indicated that measuring the ICT using DSC was a useful method to classify PEG 6000.     

Graft copolymerizations of gaseous vinyl chloride and vinylidene chloride on preirradiated polypropylene

The graft copolymerizations onto the preirradiated polypropylene fibers of gaseous vinyl chloride and also of gaseous vinylidene chloride were carried out. The fibers were preirradiated with γ-rays from a ⁶⁰Co source at ?78°C. in air to a total dose of 8 X 10⁵ rad, and were thus presumed to contain peroxide radicals which were active in grafting at ordinary temperature. The volume decrease of monomers at constant pressures due to the sorption and the grafting reaction was followed automatically at temperatures ranging from ?10 to 80°C. The net monomer consumption through the grafting process was estimated by subtracting the volume change due to the sorption from the total volume change of monomers. In general, the extent of grafting was lower at the higher grafting temperature and the decrease of the grafting activity of fibers was also accelerated. The grafting was found to increase almost linearly with the logarithm of the reaction time and the logarithm of the radiation of the radiation dose to the fibers. The extent of grafting was also proportional to the vapor pressure of monomer at a given reaction temperature and was supposed to be controlled by the amount of the monomer adsorbed. Raising the irradiation temperature higher than 0°C. brought about a marked decrease in the activity of preirradiated polypropylene. The grafting activity was successfully retained by the polymer for at least a fortnight at ?78°C.     

Rapid evaluation of charge/discharge properties for lithium manganese oxide particles at elevated temperatures

A microelectrode technique was applied to investigate the electrochemical properties of LiMn₂O₄ particles at elevated temperatures. Cyclic voltammograms of LiMn₂O₄ were measured after the particles were exposed to the electrolytes. This technique results in rapid and precise evaluation of the redox behavior of the materials. A significant capacity fading was observed in 1 M LiPF₆/EC+PC electrolytic solution, which indicates that both LiMn₂O₄ and LiPF₆ participate in the reaction to produce an inert material on the particle surface. Next, the capacity fading for two different BET surface area particles were compared using 1 M LiPF₆/EC+PC at 50 °C. The reaction was found not to be controlled by the surface area. Finally, a Li_1.1Mn_1.9O₄ particle was employed. The fading in discharge was ca. 10% for 50 cycles even at 50 °C, which means that the partial substitution of Mn in LiMn₂O₄ by Li substantially enhanced the capacity stability. Electronic Publication     

Reinvestigation of the grignard reactions with formic acid. A convenient method for preparation of aldehydes

Grignard reagents react with formic acid in tetrahydrofuran to produce aldehydes in relatively good yields Various aldehydes such as alkyl, aryl, allyl, benzyl and vinyl aldehydes were prepared from the corresponding Grignard reagents. The reaction with vinyl Grignard reagents proceeded with retention of configuration.     

Synthesis of Immunosuppressive Neoglycoproteins: Bovine Serum Albumin Coupled with 8-(Hydrazino-Carbonyl)Octyl 4- Or 6-O-α-D-Mannopyranosyl-α-D-Mannopyranoside

Abstract

Recombinant cytokines generated by bacteria, especially E. coli, are nonglycosylated. To investigate the effects of carbohydrates on their activities, we attempted to develop new cytokines by introduction of carbohydrates. As a model we synthesized neoglycoproteins in which potential immunoregulatory carbohydrates were coupled to bovine serum albumin(BSA). Mannose dimers with C9 spacer, Manα1-6Man, which is reported to be immunosuppressive, and a reference substance Manα1-4Man were synthesized as follows. Benzylidenation of 8-(methoxycarbonyl)octyl α-D-mannopyranoside (10), followed by acetylation and cleavage of the benzylidene acetal, gave a glycosyl acceptor (13) with a free hydroxyl group in the C-4 position. Glycosylation of 13 with acetobromomannose (8), followed by debenzylation, deacetylation, and hydrazidation, gave 8-(hydrazinocarbonyl)octyl 4-O-α-D-mannopyranosyl-α-D-mannopyranoside (1). Total yield of 1 from 10 was 25.1%. Tritylation of 10, followed by acetylation and detritylation, gave a glycosyl acceptor (18) with a free hydroxyl group in the C-6 position. Analogous condensation of 18 with 8, followed by deacetylation and hydrazidation, gave 8-(hydrazinocarbonyl)octyl 6-O-α-D-mannopyranosyl-α-D-mannopyranoside (2). Total yield of 2 from 10 was 22.9%. These mannose dimers were coupled to BSA by the acyl azide method. Using the antibodies against the mannose dimers, an enzyme linked immunosorbent assay (ELISA) was established to measure the small amount of mannose dimers coupled to proteins. These two neoglycoproteins appeared to inhibit the antigen-specific human T cell proliferation over 100 fold more efficiently than free mannose dimers.     

Re-examining scale elasticity in DEA

We propose a new scheme for measuring scale elasticity of production based on a new cost efficiency model developed in Tone (2002). Comparing our model with classical model we establish the superiority of our model over the latter based on the premise that the classical estimates of cost efficiency and scale elasticity can be illusory.     

Core-modified phthalocyanine analogues with a seven-membered ring unit in place of a five-membered ring unit

A variety of phthalocyanine analogues with a seven-membered ring unit in place of a five-membered ring unit were synthesized from aromatic dicarbonitriles bearing cyano groups at 1,4-separate positions. Based on the spectroscopic analyses and theoretical calculations, tetraazachlorine-like electronic structures of these novel compounds stemming from severe twist of the conjugation system at the seven-membered ring unit have been revealed.