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B. Stanovnik M. Tiler D. Gabrijel
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M. Kunaver J.
mitek 《Journal of heterocyclic chemistry》1979,16(8):1567-1570
The conversion of heterocyclic amines into the corresponding azides or tetrazoloazines under phase transfer reaction conditions is described. It was found that this transformation is limited ordy to aminopyridine ( 1a-d ) aminoisoquinoline ( 1e ) and 2-aminobenzothiazole ( 1f ) derivatives, while other heterocyclic amines ( 1g-w ) could not be transformed under these conditions. 相似文献
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Markovic Maja D. Seslija Sanja I. Ugrinovic Vukasin Dj. Kunaver Matjaz Panic Vesna V. Pjanovic Rada V. Spasojevic Pavle M. 《Cellulose (London, England)》2021,28(17):11109-11132
Cellulose - pH- and magnetic-sensitive hybrid hydrogels based on poly(methacrylic acid) (PMAA), nanocellulose (NC), carboxymethyl cellulose (CMC) and magnetite particles (MN) were prepared as... 相似文献
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Cellulose liquefaction in acidified ethylene glycol 总被引:3,自引:0,他引:3
Wood pulp cellulose was used in a study of its catalyzed liquefaction in the presence of ethylene glycol, p-toluene sulfonic acid monohydrate or sulphuric acid being the catalysts. For this study, microcrystalline cellulose, Whatman
filter paper no. 1 and cotton linters with molar masses of 76,000, 699,000 and 1,910,000 g mol−1, respectively were used. This liquefaction was studied by gravimetric determinations, by X-ray diffraction analysis of the
residual cellulose and by monitoring of the molar mass decrease over different time intervals, using size-exclusion chromatography.
The disordered regions, even of cellulose with the highest molar mass degraded in the initial minute of liquefaction. However,
the highly ordered cellulose regions remained relatively stable for a longer time. None the less, partial degradation of the
highly ordered regions of the cellulose was achieved. 相似文献
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Synthesis and characterization of biodegradable aliphatic copolyesters with poly(ethylene oxide) soft segments 总被引:1,自引:0,他引:1
A series of multiblock poly(ether-ester)s based on poly(butylene succinate) (PBS) as the hard segments and hydrophilic poly(ethylene oxide) (PEO) as the soft segments was synthesized with the aim of developing degradable polymers which could combine the mechanical properties of high performance elastomers with those of flexible plastics. The aliphatic poly(ether-ester)s were synthesized by the catalyzed two-step transesterification reaction of dimethyl succinate, 1,4-butanediol and α,ω-hydroxyl terminated poly(ethylene oxide) (PEO, = 1000 g/mol) in bulk. The content of soft PEO segments in the polymer chains was varied from about 10 to 50 mass%. The effect of the introduction of the soft PEO segments on the structure, thermal and physical properties, as well as on the biodegradation properties was investigated. The composition and structure of these aliphatic segmented copolyesters were determined by 1H NMR spectroscopy. The molecular weights of the polyesters were verified by gel permeation chromatography (GPC), as well as by viscometry of dilute solutions and polymer melts. The thermal properties were investigated using differential scanning calorimetry (DSC). The degree of crystallinity was determined by means of DSC and wide-angle X-ray scattering. A depression of melting temperature and a reduction of crystallinity of the hard segments with increasing content of PEO segments were observed. Biodegradation of the synthesized copolyesters, estimated in enzymatic degradation tests in phosphate buffer solution with Candida rugosa lipase at 37 °C was compared with hydrolytic degradation in the buffer solution. The weight losses of the samples were in the range from 2 to 10 mass%. GPC analysis confirmed that there were significant changes in molecular weight of copolyesters with higher content of PEO segments, up to 40% of initial values. This leads to conclusion that degradation mechanism of the poly(ether-ester)s based on PEO segments occurs through bulk degradation in addition to surface erosion. 相似文献
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Marta?Klanj?ek?Gunde Nina?Hauptman Marijan?Ma?ek Matja??Kunaver 《Applied Physics A: Materials Science & Processing》2009,95(3):673-680
SU8, the near-UV photosensitive epoxy-based polymer was used as a sensor layer in the capacitive chemical sensor, ready for
integration with a generic double-metal CMOS technology. It was observed that the response of the sensor slowly increases
with the temperature applied in hard-baking process as long as it remains below 300°C. At this temperature the response of
the sensor abruptly increases and becomes almost threefold. It was shown that fully crosslinked structure of the sensor layer
becomes opened and disordered when the sensor is hard-baked at temperatures between 300°C and 320°C, that is, still well below
the degradation temperature of the polymer. These changes in chemical structure were analyzed by Fourier-transform infrared
spectroscopy. The temperature-dependent changes of the sensor layer structure enable one to prepare a combination of capacitive
chemical sensors with good discrimination between some volatile organic compounds. 相似文献
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Tomaž Kos Alojz Anžlovar Matjaž Kunaver Miroslav Huskić Ema Žagar 《Cellulose (London, England)》2014,21(4):2579-2585
In this work we report on the procedure for fast and controlled preparation of nanocrystalline cellulose (NCC) from commercially available microcrystalline cellulose using microwave-assisted hydrolysis. By varying the sulfuric acid concentration and hydrolysis temperature, an average hydrodynamic diameter of NCC between 126 and 1,310 nm with corresponding yields between 16 and 82 %, respectively, was obtained in a very short reaction time of 10 min. An additional advantage of the described procedure is its high reproducibility and ability to fine-tune the average NCC particle size by adjusting the reaction conditions, i.e., the sulfuric acid concentration and/or reaction temperature. 相似文献
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