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121.
M. Nierlich L.L.B. F. Boue L.L.B. A. Lapp L.L.B. R. Oberthür I.L.L. 《Colloid and polymer science》1985,263(12):955-964
We have studied salt free semi dilute polyelectrolyte solutions by small angle neutron scattering. Specific labelling associated with an extrapolation method has allowed the separation of the form factor of a single polyelectrolyte chainS
1(q) and the structure factorS
2(q). Two lengths are deduced from these two factors: the persistence lengthb
t which characterizes the electrostatic interactions along the chain by a fitting ofS
1(q) with calculation of the scattering function for a wormlike chain, and fromS
2(q),q
m
–1
which characterizes the interactions between chains. These two lengths vary in the same way with the concentration of polyions (b
t C
p
–1/2
,q
m
–1
C
p
–1/2
) and a constant relation exists between them: only one length is then necessary to describe the structure of polyelectrolyte soltuion on this semidilute concentration range.Laboratoire Commun CEA-CNRS. 相似文献
122.
This paper discusses the kinetic simulation of TiCl4--coinitiated living carbocationic isobutylene (IB) polymerizations governed by dormant-active equilibria, using a mechanistic model. Two kinetic models were constructed from the same underlying mechanism: one using a commercial simulation software package (Predici®), and the other using the method of moments. Parameter estimation from experimental batch reactor data with Predici yielded a rate constant of propagation kp = 4.64 × 108 ± 2.75 × 108 L/mol s, with no constraints imposed. This agrees with kp data measured with diffusion clock and competition methods, but disagrees with kinetically obtained kp values. Estimation of rate constants with Predici® and the GREG parameter estimation software packages revealed that it was difficult to estimate the complete set of kinetic parameters, due to correlated effects of the parameters on model predictions. Estimability analysis confirmed that some of the strongly correlating parameters could not be estimated simultaneously using the available experimental data. Using kp = 6 × 108 ± 2.75 × 108 L/mol s measured by Mayr, and using starting estimates of other rate constants defined by experimentally observed correlations, yielded the set of rate constants required for the simulations. Both kinetic models yielded good agreement with experimental data, with the exception of Mw values that slightly diverged from the theoretically predicted ‘Mw−Mn = constant’ relationship. This may indicate the occurrence of a minor side reaction. However, the kp/k−1 = 17.5 L/mol average run length calculated from measured and simulated MWD data agrees well with earlier literature values. 相似文献
123.
利用双光束电子散斑干涉法(ESPI)对试件受热变形进行了实时观测,针对一次实验过程中得到的图片较多(300~500幅)的特点,在图像处理时摒弃了以往的手动识别等位移线的办法,用MATLAB语言编写了批处理程序,能够在采集的大量散斑图片中自动快速准确地标定等位移线,得到相应的位移和应变,并结合实时测量的温度值,获得了45钢和LY12铝合金在不同温升率下的热膨胀系数及其随温度的变化。实验结果表明,在涉及的温升率范围内,温升率的改变对材料热膨胀系数的影响不明显,材料的热膨胀系数随温度的升高略有上升。 相似文献
124.
125.
Charlotte Duval Cécile Nouvel Jean‐Luc Six 《Journal of polymer science. Part A, Polymer chemistry》2014,52(8):1130-1138
Poly(d,l ‐lactide‐co‐glycolide) (PLGA) copolyesters are commonly used in biomedical applications. Researches were carried out on nontoxic or low‐toxic catalysts that are enough efficient to provide short polymerization times, adequate microstructure chains and similar properties than the commercial PLGA materials. In this study, PLGA were synthesized by ring‐opening copolymerization (ROP) using three different catalysts. Stannous octoate is the first catalyst we used, as it is very efficient, even its toxicity is still on debate. Two others low‐toxic catalysts [zinc lactate and bismuth subsalicylate (BiSS)] were also evaluated. The comparison of these ROP was realized in terms of kinetics and control of the polymerization. Then, the influence of the catalyst on the PLGA microstructure chains is reported. Finally, abiotic hydrolytic degradation rate is studied. Results described in this article show that BiSS is one very attractive catalyst to produce low toxic PLGA for biomedical applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1130–1138 相似文献
126.
Micro-shish-kebab stirring-induced polyethylene crystals, as defined and described in the preceding paper, are flat, ribbon-shaped fibers. Selected area electron-diffraction techniques were used to determine the orientation of the crystal axes with respect to the external fiber shape. It has been shown that in addition to the crystal-lographic c-axis laying along the fiber direction, the normal to the ribbon plane is parallel to the crystallographic a-axis. 相似文献
127.
Matthew Thompson Carolyn Carkner Adrian Bailey Nicholas J. Mosey Nadia Kapernaum 《Liquid crystals》2013,40(9):1246-1260
Two sterically equivalent series of phenoxy-terminated 5-alkoxy-2-(4-alkoxyphenyl)pyrimidine liquid crystals were synthesised, and their mesogenic properties were characterised by polarised optical microscopy and differential scanning calorimetry (DSC). The phenoxy end-group causes a significant increase in melting point and inhibits – at least partially – the mesomorphism of these materials relative to the parent isomers; in most cases, the broad enantiotropic SmC phase formed by the parent isomers is suppressed by the addition of the phenoxy end-group. However, detailed analyses by small-angle X-ray scattering and monodomain 2D X-ray scattering suggest that these compounds form a SmA phase with a partially intercalated bilayer structure in which the phenoxy end-groups are nanosegregated. Such an intercalated bilayer structure might enable the tuning of smectogenic properties by appropriate substitution of the phenoxy end-groups. 相似文献
128.
ABSTRACTA homologous series of new chiral liquid crystal compounds, MnBEB (n = 4–10), was prepared by covalently linking a chiral (–)-menthyl with biphenyl-benzoate via a dicarboxylic spacer of varying length and parity. A combination of analysis methods, such as FT-IR, 1H NMR spectra, differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction was carried out to systematically investigate their phase structures and phase transition behaviours. The length and parity of the flexible spacers has a profound influence on the Tm and Tc and a modest odd-even effect is observed for the chiral liquid crystal compounds MnBEB. Only compound M4BEB developed an N* phase with selectively reflection on heating and a blue phase on cooling process. In addition, increasing the length of the flexible spacers tends to narrow the temperature range of the N* phase and widen the smectic phase, moreover, the pitch becomes longer with the spacer increases. 相似文献
129.
Tetsuo Ueda 《Phase Transitions》2013,86(2-3):93-104
By using a giant amoeboid cell of the Physarum plasmodium, changes in the intracellular distribution of chemical components are studied in relation to information processing in cell behavior. Various kinds of metabolites oscillate, and so the protoplasm should be a collection of chemical oscillators. Spatially, characteristic chemical patterns are self-organized for different cell shapes, and hence cell behavior. New phase waves propagate throughout the cell upon local stimulation, their direction being opposite for attraction and repulsion. Locomotion is inhibited when the coherence of the oscillators breaks. Thus, pattern dynamics is correlated with information processing in the amoeboid cell. 相似文献
130.
F. L. Vook 《辐射效应与固体损伤》2013,168(3-4):155-160
This paper was given as the opening address at the 1970 Albany International Conference on Radiation Effects in Semiconductors, and it attempts to establish a general overview of the field by concentrating on recent research developments and important unanswered questions. The continuing importance of impurity-defect interactions, of microscopic defect identification, and of the necessity for more theoretical calculations are emphasized. The rapid development of the field of ion implantation and its close relationship with radiation effects studies are pointed out. It is predicted that research in compound semiconductors will increase rapidly with close beneficial interaction with ion implantation studies. 相似文献