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1.
J. S. Chiou J. W. Barlow D. R. Paul 《Journal of Polymer Science.Polymer Physics》1987,25(7):1459-1471
The miscibility of bisphenol-A polycarbonate (PC) with poly(methyl methacrylate) (PMMA) has been reexamined using differential scanning calorimetry (DSC) and optical indications for phase separation on heating, i.e., lower critical solution temperature (LCST) behavior. Various methods have been used to prepare the blends including methylene chloride (CH2Cl2) and tetrahydrofuran (THF) solution casting, melt mixing, and precipitation of PC and PMMA simultaneously from THF solution by using the nonsolvents methanol and heptane. It is shown that the resulting phase behavior for PC/PMMA blends is strongly affected by the blend preparation method. However, these blends are miscible over the whole blend composition range (unambiguous single composition-dependent Tg's and LCST behavior) when prepared by precipitation from solution using heptane as the nonsolvent. To the contrary, solution-cast and melt-mixed PC/PMMA blends were all phase separated, which may be attributed to the “solvent” effect and LCST behavior, respectively, not discovered in previous reports. Methanol precipitation does not lead to fully mixed blends, which demonstrates the importance of the choice of nonsolvent when using the precipitation method. 相似文献
2.
Summary Consider a reversible Markov chain X
n
which takes values in a subset of d. If the steps of the chain are uniformly bounded and the invariant measure satisfies a mild regularity condition, Varopoulos, Carne and Kesten have obtained estimates on
\lambda n^{1/2} )$$
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which exhibit a Gaussian tail in but blow up as n. Following Kesten's approach we derive bounds which are uniform in n in some special cases. Our main result, however, is an example which shows that in general the estimates of Varopoulos, Carne and Kesten are essentially best possible.Research partially supported by an S.E.R.C. (U.K.) visiting fellowship and an operating grant from N.S.E.R.C. of Canada 相似文献
3.
Strong, low-energy two-photon absorption in extended amine-terminated cyano-substituted phenylenevinylene oligomers 总被引:8,自引:0,他引:8
Chung SJ Rumi M Alain V Barlow S Perry JW Marder SR 《Journal of the American Chemical Society》2005,127(31):10844-10845
Three quadrupolar oligophenylenevinylenes with five rings in the conjugated backbone, terminal donor groups, and various acceptors and/or donors along the backbone were synthesized and their two-photon spectroscopic properties investigated. These chromophores exhibit large two-photon absorption cross sections over a wide wavelength range and two distinct peaks, the strongest of which (deltamax > 3600 GM) is observed at 960-970 nm, a wavelength close to twice the value of the linear absorption maximum (2lambda(1)max). The findings on these chromophores are compared with those for analogous molecules with shorter conjugation length, for which the main two-photon band is at significantly shorter wavelength than 2lambda(1)max. 相似文献
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Richard Partch Egon Matijevi Anthony W. Hodgson Barlow E. Aiken 《Journal of polymer science. Part A, Polymer chemistry》1983,21(4):961-967
A procedure was developed by which polymer colloids can be prepared by polymerizing aerosol droplets of monomers with an initiator in the vapor state. This work describes the formation of poly(p-tertiarybutylstyrene) particles by exposing the corresponding monomer droplets to trifluoromethanesulfonic acid. It was found that the monomer-to-initiator mass ratio is the critical factor in determining the uniformity and morphology of the particles. Under ideal conditions spheres of narrow size distribution are obtained. Otherwise porous particles or soft particles with whiskers may develop. The aerosol was prepared in a falling film generator, but other procedures for producing monomer droplets may be used. 相似文献
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8.
Jones SC Hascall T Barlow S O'Hare D 《Journal of the American Chemical Society》2002,124(39):11610-11611
The bimetallic complexes [M(CO)(3)](2)(mu:eta(5):eta(5)-Pn) (Pn = pentalene, C(8)H(6); M = Mn, Re) have been synthesized and characterized crystallographically; the Mn compound was isolated as solely the anti-isomer, while the Re analogue was formed as a mixture of anti- and syn-isomers. [Mn(CO)(3)](2)(mu:eta(5):eta(5)-Pn) may be reduced chemically to its mono- and dianions; the mixed-valence Mn(I)/Mn(0) monoanion is shown by ESR, vibrational, and electronic spectroscopies to be a Robin-Day class III system with an exceptionally large electronic coupling between the metal centers. 相似文献
9.
The complex nature of biofluids demands efficient, sensitive and high-resolution analytical methodologies to examine how the 'metabolic fingerprint' changes during disease. This paper describes how sulphated beta-cyclodextrin-modified micellar electrokinetic capillary chromatography (SbetaCD-MECC) has been combined with data alignment analysis and may prove a useful new tool in urine profiling, allowing for separation of over 80 urinary analytes in under 25 min. The optimised and validated SbetaCD-MECC methodology combined with data alignment analysis provides rapid identification of 'mismatches' between urine profiles which are not easily detected with the naked eye as well as a 'similarity score' which indicates the total sum of differences between one profile and another. The combination of SbetaCD-MECC with data alignment software should prove a useful alternative tool in metabonomic studies for rapid comparison of urine profiles. 相似文献
10.
The dehydro[3](1,1′)ferrocenophanes, 1,1′-(1-propene-1,3-diyl)-ferrocene (3a), and 1,1′-(3-phenyl-1-propene-1,3-diyl)-ferrocene (3b) were synthesised under Shapiro conditions from the tosylhydrazones of the corresponding α-oxo-[3](1,1′)ferrocenophanes. Electrochemistry shows 3a is oxidised at smilar potential to ferrocene; according 3a can be chemically oxidised using silver trifluoromethanesulfonate. The structure of 3a shows a ring tilt of 11.3°. Attempts to polymerise 3a using the ROMP initiator Mo(CHCMe2Ph)[N(2,6-iPr2C6H3)][OCMe(CF3)2]2 led to a mixture of insoluble material and a soluble mixture of apparently cyclic oligomers ([3a]n). 相似文献