排序方式: 共有41条查询结果,搜索用时 15 毫秒
1.
Pirita Rämänen Paavo A. Penttilä Kirsi Svedström Sirkka Liisa Maunu Ritva Serimaa 《Cellulose (London, England)》2012,19(3):901-912
Cellulose whiskers were prepared from wood- and cotton-based microcrystalline cellulose and dried by two methods: freeze-drying
or air-drying. The effect of drying method on the properties and structure of the whiskers were studied. Furthermore, the
influence of the source of cellulose on the nanoscale structure was investigated. Drying method was observed to slightly influence
the thermal stability of cellulose whiskers, whereas the char residue varied significantly depending on the drying process
performed. Small- and wide-angle X-ray scattering and solid state nuclear magnetic resonance spectroscopy were used to examine
the crystallinity and nanoscale structure of the dried whiskers. It was observed that the crystal structure and crystallinity
of cellulose whiskers remained during all treatments, whereas their nanoscale structure was significantly influenced by drying
method, neutralization, and source of cellulose. Relationships between thermal behavior and nanoscale structure were reported
and discussed. 相似文献
2.
Tiia‐Riikka Tero Dr. Kirsi Salorinne Dr. Heli Lehtivuori Prof. Janne A. Ihalainen Prof. Maija Nissinen 《化学:亚洲杂志》2014,9(7):1860-1867
An unexpected and previously unknown resorcinarene mono‐crown with a fused benzofuran moiety in its macrocyclic core was obtained as a byproduct from a bridging reaction of tetramethoxy resorcinarene with tetraethylene glycol ditosylate. The formation of the fused benzofuran moiety in the resorcinarene macrocycle resulted in a unique rigid and puckered boat conformation, as shown by XRD studies in the solid state. Modification of the macrocycle was also observed to affect the photophysical properties in solution by enhancing the fluorescence brightness compared with a conventional resorcinarene macrocycle. The fluorescent properties enabled unique detection of structural features, that is, the rigid boat conformation with the conjugated benzofuran system and the more flexible crown bridge part, in solution. 相似文献
3.
Applying human and pig hepatic in vitro experiments for sulfur mustard study: Screening and identification of metabolites by liquid chromatography/tandem mass spectrometry 下载免费PDF全文
4.
Heiskanen JP Omar WA Ylikunnari MK Haavisto KM Juan MJ Hormi OE 《The Journal of organic chemistry》2007,72(3):920-922
Quinolines with a hydroxyl group at the 8-position and an alkoxy group at the 4-position are rare compounds. In this paper the synthesis of five 4-alkoxy-8-hydroxyquinolines is reported. The key reaction in the synthetic route is a selective protection of the hydroxyl group at C-atom 8 in 4,8-dihydroxyquinoline with a tosyl group and the hydrolytic removal of the protective group after the alkylation. The tosyl group is stable during the alkylations with various alkylating agents in the presence of sodium hydride. 相似文献
5.
6.
Harju K Vahermo M Mutikainen I Yli-Kauhaluoma J 《Journal of combinatorial chemistry》2003,5(6):826-833
The solid-phase synthesis of 1,2,3-triazoles via 1,3-dipolar cycloaddition of polymer-bound azides to various alkynes is reported. Polymer-bound azides were synthesized from polymer-bound halides and sodium azide and reacted with alkynes to produce polymer-bound 1,2,3-triazoles. Cleavage of the triazoles was performed with trifluoroacetic acid. A traceless synthesis of 1,2,3-triazoles was developed using 2-methoxy-substituted resin (polymer-bound 4-hydroxy-2-methoxybenzyl alcohol). In addition, a synthesis of 4-hydroxybenzyl-substituted 1,2,3-triazoles from the bromo-Wang resin (4-(bromomethyl)phenoxymethyl polystyrene) was achieved. 相似文献
7.
Sebastian Kröner Kirsi Eloranta Michiel F. Bergstra Michael Bartke 《Macromolecular Symposia》2007,259(1):284-294
Summary: The kinetic behaviour of a supported metallocene catalyst in slurry polymerisation of ethylene with 1-hexene under industrially relevant reaction conditions has been studied. Polymerisation experiments were carried out in a 5-litre stirred tank reactor in a temperature range from 60 to 80 °C and ethylene partial pressures from 5 to 15 bar. Comonomer and hydrogen amounts were varied as well. The catalyst showed pronounced activation and slow deactivation during runtimes of about 1 hour. Strong influences of 1-hexene (“hexene effect”) and hydrogen (“hydrogen effect”) on the activity profiles were observed. Based on the experimental results, a kinetic model has been derived in order to describe and predict important polymerisation data such as activity profile, comonomer content and molecular weight distributions with respect to the reaction conditions. The presented kinetic model is able to describe the observed effects of 1-hexene and hydrogen on the activity profiles, as well as the comonomer incorporation across a broad range of polymerisation conditions. The molecular weight distributions can be simulated with good qualitative agreement to the experimental data. 相似文献
8.
Harju K Kylänlahti I Paananen T Polamo M Nielsen J Yli-Kauhaluoma J 《Journal of combinatorial chemistry》2006,8(3):344-349
Study was made of the 1,3-dipolar cycloaddition of polymer-bound alkynes to azomethine imines generated in situ from N-aminopyridine iodides. Aromatization of the cycloadducts gives polymer-bound pyrazolopyridines that can be released from the resin as carboxylic acids with trifluoroacetic acid or as methyl esters with sodium methoxide. 相似文献
9.
Yingfeng Shen Hannes Orelma Asko Sneck Kirsi Kataja Juha Salmela Pia Qvintus Anna Suurnäkki Ali Harlin 《Cellulose (London, England)》2016,23(6):3393-3398
A new process for preparing thin cellulose nanofibril (CNF) filaments (thickness of 16 µm) was investigated by utilizing the dry spinning approach. In the process, CNF hydrogel was extruded through a fine nozzle onto an adhesion controlled capstan (drum) with low friction (slippery surface) at a speed of up to 11 m/s. The utilized capstan enables excellent line speed control when the slippery surface is applied, and prevents drying shrinkage of the spun filaments. The mechanical properties of prepared filaments can be optimized with the stretch ratio, the ratio of the speed of the drum surface, and the CNF jet flow. The developed method allows for manufacturing thin CNF filaments with an elevated spinning rate in a more controlled manner. 相似文献
10.
van der Waals interactions are critical in Car–Parrinello molecular dynamics simulations of porphyrin–fullerene dyads 下载免费PDF全文
Topi Karilainen Oana Cramariuc Mikael Kuisma Kirsi Tappura Terttu I. Hukka 《Journal of computational chemistry》2015,36(9):612-621
The interplay between electrostatic and van der Waals (vdW) interactions in porphyrin‐C60 dyads is still under debate despite its importance in influencing the structural characteristics of such complexes considered for various applications in molecular photovoltaics. In this article, we sample the conformational space of a porphyrin‐C60 dyad using Car–Parrinello molecular dynamics simulations with and without empirical vdW corrections. Long‐range vdW interactions, which are poorly described by the commonly used density functional theory functionals, prove to be essential for a proper dynamics of the dyad moieties. Inclusion of vdW corrections brings porphyrin and C60 close together in an orientation that is in agreement with experimental observations. The structural differences arising from the vdW corrections are shown to be significant for several properties and potentially less important for others. Additionally, our Mulliken population analysis reveals that contrary to the common belief, porphyrin is not the primary electron donating moiety for C60. In the considered dyad, fullerene's affinity for electrons is primarily satisfied by charge transfer from the amide group of the linker. However, we show that in the absence of another suitable bound donor, C60 can withdraw electrons from porphyrin if it is sufficiently close. © 2015 Wiley Periodicals, Inc. 相似文献