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991.
Joy Chakraborty Brajagopal Samanta Andrei S. Batsanov Joan Ribas M. Salah El Fallah Samiran Mitra 《Structural chemistry》2006,17(4):401-407
A ligand–metal–ligand type co-ordination polymer [Ni (C6H12N4)(NCS)2(H2O)2]
n
has been synthesised under controlled hydrothermal conditions. Here 1,3,5,7-tetraazatricyclo[3.3.1]decane [or hexamethylenetetramine (hmt)] has been used as a μ-(N,N′) bidentate spacer molecule. The prepared polymeric complex has been characterised by elemental and spectral analyses. The structure has been confirmed by a single crystal X-ray diffraction study. Magneto-structural correlation has been drawn from cryomagnetic susceptibility measurements (2–300 K) which unequivocally reflects very weak magnetic spin interactions among the long distant octahedral Ni(II) metal centres mediated by hmt and weak hydrogen bonding interactions between the adjacent zigzag one-dimensional polymeric chains carrying into a two-dimensional infinite polymeric framework. 相似文献
992.
993.
Water-in-Oil high internal phase emulsions (HIPEs) whose continuous phase is polymerizable gave access to highly porous polymeric
materials (polyHIPEs). These emulsions were prepared with a laboratory-made homogenizer whose shear frequency and time could
be varied to study the influence of the emulsification conditions on the polyHIPEs morphology. Intensive and/or long shear
induced a reduction of the cell and connection diameters without any modification of the material global porosity. The mechanical
properties were evaluated by estimating the Young’s modulus from compression tests. The mechanical behavior was analogous
for all materials possessing a characteristic polyHIPE structure, even if cell sizes were different between samples. 相似文献
994.
M. V. Opanasenko Zh. V. Chernenko V. G. Il’in 《Theoretical and Experimental Chemistry》2008,44(6):380-385
A comparative study was carried out on the matrix polymerization of divinylbenzene, acrylonitrile, and methyl methacrylate
in SBA-15 silica mesoporous molecular sieves. The occupancy of the matrix mesopores by the starting monomer, the medium, the
polymerization temperature and time as well as the means of removing the exotemplate were all found to affect the spatial
organization and porous structure of the polymer materials. Surplus occupancy of the mesopores by the monomer (1–1.5), polymerization
in vacuum, and an alkaline method for matrix removal were found to be optimal. IR spectroscopy was used to find the conversion
of the starting polymer by following the relative change in intensity of the vinyl group bands.
Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 371–375, November–December, 2008. 相似文献
995.
Sambhu Bhadra 《European Polymer Journal》2008,44(6):1763-1770
Substitution in aniline has tremendous effect in the synthesis of poly(substituted anilines) as well as in their properties. In this investigation polyaniline (PANI), poly(m-nitro aniline) (PMNA), poly(m-amino phenol) (PMAP) and poly(o-ethyl aniline) (POEA) were synthesized by oxidative polymerization under identical conditions. Different properties were measured and compared with PANI to find out the presence of electron donating -OH group, electron withdrawing -NO2 group and less effecting ethyl group on the properties of poly(substituted anilines). It was found that presence of any type of substitution in the benzene ring of aniline increases the solubility of the resulted polymer but reduces the yield, degree of polymerization, thermal stability, electrical and thermal conductivity. The colors, bulk density, particle size, percentage of crystallinity vary considerably depending on the nature of substitution. 相似文献
996.
Polymer materials used in railway field are degraded by environmental factors such as thermal, oxidative, photolytic, hydrolytic, and mechanical. The expected service life of the polymer materials used in railway field is approximately 20 years that is relatively long period for the polymer material; therefore, respective degradation factors should be well considered. Some of the degradation conditions indicate similar mechanism. The oxidative reaction was seen in every degradation conditions under air atmosphere. The hydrolytic reaction was mainly observed in chemical and biological degradations. The degradation behavior of the polymer material was analyzed by various methods. FTIR, thermal analysis (TG, DSC), and molecular weight determination were mainly applied for its purpose. However, the degradation mechanism of practical products made of polymer material was insufficiently studied and the exchange criteria of the products depended on the visual inspection without the suitable degradation analysis not only in the railway field but also in other commercial and industrial fields. In addition, most of the methods to analyze degradation of polymer material are performed on the standard specimen forms. For the installed product, some kinds of damage are generated through the sample collection process; therefore, the damaged products have to be exchanged for brand new ones or repaired totally to be used for more period. Moreover, it is hard to suspend the railway service for the degradation analysis of polymer products. From these backgrounds, the prospect of degradation analysis related to polymer materials used in railway field was proposed. 相似文献
997.
998.
M. Yu. Balakina 《Russian Chemical Bulletin》2008,57(7):1351-1355
The effect of organic chromophores incorporated into a polymer electret and responsible for its nonlinear optical (NLO) response
to an applied electric field on the electrostriction coefficients (ESC) of the material is studied. Analytical expressions
for the ESC were derived in the framework of a model proposed earlier, which includes the effect of a locally anisotropic,
polarizable and deformable environment on the electric characteristics of the chromophore. The dependence of the ESC on both
macroscopic and microscopic parameters of the molecular system is established. Numerical estimates of the ESC for poly(methyl
methacrylate) doped with the dye Disperse Red 1 and dimethylaminonitrostilbene-doped polycarbonate agree with experimental
data in order of magnitude. The relations obtained can be used in the design of novel organic NLO materials.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1324–1329, July, 2008. 相似文献
999.
Antimicrobial-modified starch was synthesized by covalently bonding guanidine polymer (PHGH) with potato starch via coupling
reaction. Orthogonal tests were applied to optimize the reaction conditions. The coupling efficiency could reach 90.21% at
the optimal conditions: temperature, 70 °C; time, 2 h; PHGH/starch, 120 wt.%; GDE/starch, 8 wt.%; pH, 11. PHGH modified starches
exhibited high antimicrobial activities against both E. coli and S. aureus. Shaking flask method was more suitable for current non-released modified starches than diffusion method to evaluate the antimicrobial
activities. In the presence of 1.0 wt.% PHGH in wood fibers, the growth inhibition reached almost 100%. The AFM results also
demonstrated that the antimicrobial mechanism of PHGH was to destroy the membrane of the cells. 相似文献
1000.
Sadia Ameen Vazid Ali M. Zulfequar M. Mazharul Haq Mushahid Husain 《Central European Journal of Chemistry》2006,4(4):565-577
The temperature dependence of direct current (dc) conductivity was studied for various samples of polyaniline-polyvinylchloride
(PANI-PVC) blended films. Polyaniline was doped with different concentrations of sulfamic acid in aqueous tetrahydrofuran
(THF) and the blended films were prepared by varying the amount of doped PANI relative to a fixed amount of PVC. The dc conductivity
of PANI-PVC blended films was measured to determine the effect of sulfamic acid (dopant) in the temperature range (300–400K).
The mechanism of conduction is explained by a two-phase model. In order to evaluate the effect of the dopant, conductivity-derived
parameters such as the pre-exponential factor (σ
o) and the activation energy (ΔE) were calculated. The structural changes of polyaniline-PVC blended films were characterized
by FTIR spectroscopy that explores information about the suitability of the dopant in the chemical doping process. 相似文献