排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
Torsten Meyer Thomas Hellweg Stefan Spange Stephanie Hesse Christian Jger Cornelia Bellmann 《Journal of polymer science. Part A, Polymer chemistry》2002,40(18):3144-3152
Polyvinylamine hydrogels with silica particles encapsulated (PVAm/silica) were produced by a two‐step synthesis. In the first step, polyvinylformamide/silica (PVFA/silica) hybrids were synthesized from vinylformamide (VFA) and 1,3‐divinylimidazolidin‐2‐one (1,3‐bisvinylethyleneurea, BVU), as the crosslinker, by radical copolymerization in silica/water suspensions using different compositions of VFA/BVU. The target product PVAm/silica was obtained by acidic hydrolysis of the PVFA/silica hydrogels in a second step. The chemical structures of both hydrogels, PVFA/silica and PVAm/silica, respectively, were revealed by solid‐state 13C(1H) cross‐polarity/magic‐angle spinning NMR spectroscopy. Both hydrogels swelled significantly in water. The swelling capacity of the two systems was characterized by the correlation length ξ (or hydrodynamic blob size) of the network meshes with small‐angle neutron scattering experiments. ξ is significantly larger for PVAm/silica than for PVFA/silica, which corresponds to the observed higher swelling capacity of this polyelectrolyte material. Furthermore, the swelling behavior of the hybrid hydrogels was quantitatively described in terms of free swell capacity, centrifuge‐retention capacity, adsorption against pressure, and free swell rate as compared with values of the corresponding copolymer hydrogels. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3144–3152, 2002 相似文献
2.
Kristin fischer Stefan Spange Steffen Fischer Cornelia Bellmann Jörg Adams 《Cellulose (London, England)》2002,9(1):31-40
The surface polarity of native celluloses has been investigated by the following solvatochromic dyes: dicyano-bis (1,10)-phenanthroline iron (II) Fe(phen)2 (CN)2 (1), bis(4-N,N-dimethylamino)-benzophenone (2), and cou-marine 153 (3). Linear Solvation Energy (LSE) relationships and the UV/Vis data have been used to characterize the surface polarity of different native cellulose batches in terms of the empirical Kamlet–Taft polarity parameters (hydrogen bond acidity), (hydrogen bond basicity), and * (dipolarity/polarizability). , , *and calculated Reichardt's E T (30) values are reported for various native and regenerated cellulose samples with different degrees of crystallinity. The degree of crystallinity of the cellulose samples has been determined by X-ray. The microcrystalline environment of cellulose can be exactly parameterized in terms of the , and *values. It shows a fairly strong acidity and a low dipolarity/polarizability. For the amorphous sections smaller and larger * values are observed. The correspondence of the empirical polarity parameters determined has been discussed in relation to results from pyrene fluorescence and zetapotential measurements. 相似文献
3.
C. Bellmann A. Opfermann H.-J. Jacobasch H.-J. Adler 《Analytical and bioanalytical chemistry》1997,358(1-2):255-258
In the field of corrosion prevention, the characterisation of metal surfaces is useful to obtain information about the necessary
preparation of the surface and about the quality of thin coatings of coupling and protective agents. Electrokinetic measurements
can be used to determine the properties of modified polymer surfaces, metal sheets, and different surface preparations. However,
it was necessary first to create special conditions for measuring the streaming potential, such as electrical isolation of
the sample sheets together with the use of inert systems, as shown by the example of aluminium. According to the usual procedure
the metal was first coated with a thin layer of a coupling agent. The effect of this adhesive agent depends on the degree
of its adsorption by the metal surface. The quality of this layer can be characterised by streaming potential measurements,
which can show the degree of coverage, the adhesive strength of the coated layer, and the effective chemical properties of
the treated surface. These results were confirmed by wetting measurements. The production of surfaces which allow us to couple
a coating varnish to the adhesive agent in good quality was demonstrated.
Received: 24 June 1996 / Revised: 30 January 1997 / Accepted: 30 January 1997 相似文献
4.
Yaremko ZM Tkachenko NH Bellmann C Pich A 《Journal of colloid and interface science》2006,296(2):565-571
The colloidal stability of TiO2 dispersions in aqueous solutions was studied. Aqueous solutions of ATLAS G-3300 (1.57 x 10(-3) mol/l), TRITON X-100 (5 x 10(-5) mol/l), and PMAA (4 x 10(-6) and 5.81 x 10(-3) mol/l) have been used as medium for redispergation of TiO2 particles. Stability of dispersions was investigated at different pH values by two different methods. By using analytical centrifuge the sedimentation velocity of TiO2 particles was directly measured and by means of light scattering the particle size of dispersed particles has been monitored. Combination of these two methods allowed determination of the aggregation degree of TiO2 particles as well as structure of the aggregates formed in aqueous phase. It has been found that redispergation process does not provide complete separation of virgin TiO2 particles. Even in the case of stable dispersions some aggregates were found, which consisted of 2-4 virgin TiO2 particles. With increasing colloidal stability of dispersions aggregates appear to be spherically shaped. In the system where TRITON X-100 was used, formation of secondary aggregates by fusion of primary ones was observed. 相似文献
5.
Fully printed flexible audio system on the basis of low‐voltage polymeric organic field effect transistors with three layer dielectric 下载免费PDF全文
Georg C. Schmidt Daniel Höft Katherina Haase Maxi Bellmann Bahman Kheradmand‐Boroujeni Tomi Hassinen Henrik Sandberg Frank Ellinger Arved C. Hübler 《Journal of Polymer Science.Polymer Physics》2015,53(20):1409-1415
Fully mass printed, flexible and truly polymeric organic field effect transistors consisting of a three layer dielectric made of CYTOP (low‐k), PVA (intermediate) and P(VDF‐TrFE‐CTFE)(high‐k) are introduced. Gravure‐, flexo‐and screen printing were selected as highly productive manufacturing technologies. These OFETs work at strongly reduced voltages and show high field effect mobility (µ = 0.2 cm2/Vs) and remarkable good bias stress stability at very high current density (50 µA/mm). Fully printed OFETs are used for the realization of ring oscillators working in the kHz regime at reduced supply voltage (10 V). In combination with printed fully polymeric piezoelectric loudspeakers, this work shows for the first time fully printed flexible audio systems. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1409–1415 相似文献
6.
R. Bellmann 《Mathematische Annalen》1976,222(1):49-54
Ohne Zusammenfassung 相似文献
7.
The impact of a rotating magnetic field (RMF) on the axial segregation in Vertical Gradient Freeze (VGF) grown, Ga doped germanium is investigated. Growth experiments were performed using the VGF‐RMF as well as the conventional VGF technique. Carrier concentration profiles characterising the Ga segregation were measured by the Spreading Resistance method and calibrated using Hall values of carrier concentration and mobility. The Ga concentration rises more gradually under RMF action, i.e., the dopant segregation is significantly reduced by the rotating field. This effect is attributed to a better mixing of the melt. Numerical results on the flow velocity confirm this explanation. The RMF induced flow is much more intense than the natural buoyant convection due to the radial temperature gradient and leads to a pronounced decrease of the effective partition coefficient keff. In the early stages of growth a keff value close to k0 was obtained, i.e., the gallium was almost homogeneously distributed within the melt. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Stefan Spange Hardy Müller Christian Jäger Cornelia Bellmann 《Macromolecular Symposia》2002,177(1):111-124
Silica particles with different morphology have been functionalized with carbon shells by different synthetic procedures. In the key step, the bare silica particles are functionalized by a specific cationic surface polymerization with furfuryl alcohol (FA). The polyfurfuryl alcohol (PFA)/silica hybrid particles have been also post-functionalized with maleic anhydride (MSA) by a Diels Alder reaction. Simultaneously occuring cationic polymerization of FA and sol-gel process with TEOS has been used for producing interpenetrating carbon-silica hybrid materials. The thermal transformation of the PFA component on silica into the carbon phase has been carried out under argon atmosphere in a temperature range from 700°C to 900°C. The influence of the former morphology of the silica on the homogenity of the resulting carbon layer is shown by zetapotential measurements and electron microscopic investigations. 相似文献
9.
L -(+)-bornesitol has been isolated from the leaves of G. lutea L . in the proportion of 1,6% by weight of dried material. Meso-inositol has also been detected by chromatography. Distribution of L -(+)-bornesitol and its taxonomic interest are discussed. 相似文献
10.
G. Valensi R. H. Crist F. B. Brown L. Williams A. H. Wilson Busby L. S. Echols Jr M. A. Smith F. L. Hayes C. H. Townes H. K. Alber A. Knoll J. Schukal E. P. Barrett W. E. Holbrook J. S. Blair A. V. Grosse W. N. Ipatjew H. J. Hall G. B. Bachman A. Klemenc A. Stock H. Kühne A. Bellmann J. Haller W. H. Albrecht K. P. GRohr H. Hillemann H. A. Wilhelm W. MacNevin H. S. Clark K. R. More R. F. Humphreys W. W. Watson P. A. Anderson G. Atchison D. O. Holland H. Sieben T. Langer 《Analytical and bioanalytical chemistry》1944,127(1):197-202