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101.
Jane?Jin John?C.?Achenbach Shiping?ZhuEmail author Yingfu?Li 《Colloid and polymer science》2005,283(11):1197-1205
The influences of polymer-related properties such as molecular weight, charge density, counter ion, and hydrophilic block
on the complexation of polyelectrolytes and a fluorescein-labeled oligonucleotide (ON) were investigated. A series of well-defined
and well-controlled 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) polymers and block copolymers were prepared using living anionic and radical polymerization
methods. Fluorescence measurement was used to reveal the effects of polymer molecular weight, charge density, and counter
ion type on the complexation. PolyDMAEMA samples having double molecular weights of the chosen oligonucleotide gave the optimal
complexation performance. Kinetic studies showed that high-molecular weight/high-charge density polymer samples produced very
stable complexes. The fully charged polyDMAEMA displayed the strongest binding with the ON. These complexes were therefore
less sensitive to the changes in the environment. PolyDMAEMA–DMSQ samples had slightly higher complexation ability than polyDMAEMA–MCQ
(DMSQ: dimethylsulfate quat; MCQ: methylchloride quat). Both poly(DMAEMA-b-HEMA) and poly(DMAEMA–MCQ-b-PEG) block copolymers
showed good complexation ability and steric stability [HEMA: 2-hydroxyethyl methacrylate; PEG: poly(ethylene glycol)]. PEG,
but not HEMA block, enhanced the effectiveness of polyDMAEMA–MCQ binding with the ON. 相似文献
102.
Stribeck N 《Analytical and bioanalytical chemistry》2003,376(5):608-617
The prospects of a modern analysis of nanostructure evolution during the processing of polymer materials by means of scattering from synchrotron radiation are demonstrated in examples. The beam sources have gained stability, shortages are located in beamline setups and in method development for the quantitative analysis of voluminous data sets.By using the proposed multidimensional chord distribution function (CDF) analysis method, nanostructure information from small-angle X-ray scattering (SAXS) data are extracted and visualised. The method can be automated if the beamline setup is able to deliver a full data set with simple constraints. In this case even a simultaneous data evaluation is possible (while one pattern is accumulated, the previous one is analysed). The advantages of the method are demonstrated in a study of the straining of a thermoplastic elastomer. The possibilities of an automated analysis are demonstrated in an investigation of the crystallisation behaviour of high-pressure injection-moulded polyethylene (HPIM-PE). The achievable results of nanostructure analysis of polymer materials are discussed. It is shown that the time-resolved SAXS of polymer materials studied during a transformation and analysed by the CDF method is not just a powerful tool to investigate the relationship between structure and properties of materials; the information that can be gained concerning the processes that control nanostructure evolution is equally important. In the future the enlightenment of such relationships may help to tailor polymer materials with respect to their properties and, beyond that, to improve assessments concerning their aging. 相似文献
103.
于铂电极上修饰一层N-(3-二茂铁乙酰胺基)丙基吡咯聚合物膜,应用循环伏安法对聚合物的电化学性能进行研究,发现了N-位取代吡咯聚合物的电活性大大降低,聚合物中 二茂铁基团氧化还原性能稳定,制成酶电极后,在+0.2V以葡萄糖有一明显的催化峰,而对抗坏血酸,尿酸则几乎没有呼应,该葡萄糖电极性能稳定,连续工作十天,响应值基本不变。 相似文献
104.
Molten polymer process streams are difficult to analyze either in- or on-line because of sampling problems due to the high temperature and viscosity of the molten state. Real-time monitoring of chemical compositions in these processes can significantly improve safety and product quality and minimize process costs and waste. The information content of the mid-infrared spectrum combined with the recent development of rugged process Fourier transform (FT) IR spectrometers is stimulating the application of process FT-IR to industrial polymer melt processes. Sampling considerations for polymer melts are reviewed. Also, the use of FT-IR spectrometry for on-line measurements of the polymer composition for polymer blends and copolymers in the melt, and the question of how this information could be used to monitor and control the quality of the product given by the process are discussed. 相似文献
105.
K. E. Collins M. L. M. M. Granja R. G. Pereira Filho T. A. Anazawa I. C. S. F. Jardim 《Chromatographia》1997,45(1):99-103
Summary Poly(methyloctylsiloxane) (PMOS), sorbed into the pores of HPLC silica particles by solvent evaporation, can function as a
useful stationary phase for reversed-phase chromatography. The present work addresses the question of how the PMOS is distributed
in the pores. Measurements of the surface area (BET, N2) of a series of partially loaded samples (0–40% PMOS, m/m) using a typical batch of HPLC silica (10 μm irregular particles
with 6 nm pores) show that the specific surface area of the samples decreases linearly with the specific loading (mass of
PMOS per gram of silica). This result is not consistent with a “film” model in which the PMOS is deposited uniformly on the
pore walls, but is consistent with a model in which long segmented “plugs” of PMOS are deposited within the pore system.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
106.
K. Sreenivasan 《Chromatographia》1986,22(1-6):199-200
Summary A modified procedure for the identification of separated components in paper chromatography using attenuated total reflection infrared spectroscopy is described. This combined method, though inferior in sensitivity and resolution to the modern separation systems interfaced with sophisticated analytical instruments, is simple, relatively less expensive and suitable for routine analysis of components like polymer additives. 相似文献
107.
108.
The plastic deformation mechanism operating in polymer glasses is analyzed. The whole process consists of two main stages: nucleation of special shear defects, called PSTs (plastic shear transformations), and their disappearance. The important feature of plastic deformation of glasses is the storage of a large amount of internal energy ΔUdef upon straining. Such energy storage is the critical issue for mechanical performance of polymeric material: if the amount of stored energy is high, the appearance of macroscopic failure is very probable while glassy materials collecting a small amount of stored deformation energy are quite ductile. It is proposed that the rate of disappearance of PSTs is a key factor in dissipation of stored deformation energy. A parameter describing the dissipation ability of material upon deformation is introduced. 相似文献
109.
Monwar M Oh SJ Rinaldi PL McCord EF Hutchinson RA Buback MM Latz H 《Analytical and bioanalytical chemistry》2004,378(6):1414-1427
Poly(n-butylacrylate-co-carbon monoxide-co-ethylene) (polyEBC) samples prepared from 13C-labeled monomer, n-butyl acrylate, were characterized using two dimensional (2D) pulsed field gradient (PFG) 750 MHz NMR spectroscopy. To elucidate the complex structure of the terpolymer, 2D-1H/13C-heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) experiments were conducted by selectively exciting the enhanced resonances in the spectra of two polymer samples, one polymer resulting from synthesis with 1-13C-n-butylacrylate monomer and a second polymer obtained from a synthesis with 2-13C-n-butylacrylate monomer. High-resolution 2D-NMR combined with 13C-labeling of the polymer greatly simplifies the 2D-NMR spectra, selectively enhances the weak peaks from low occurrence B-centered triad structures, and aids in their resonance assignments. In all experiments, the sample temperature was 120 degrees C, to ensure a homogeneous solution and sufficient molecular mobility. Electronic Supplementary Material: Supplementary material (1D 13C NMR spectra of the 13C-labeled and unlabeled polymers) is available in the online version of this article at http://dx.doi.org/100.1007/s00216-003-2402-3. 相似文献
110.