Poly broad band

In Figure 12a (Pd Pt = 1 2) and 12b (Pd Pt = 1 1), only the spectral feature of CO adsorbed on the Pt atoms, i.e., a strong band at 2068 cm and a very weak broad band at around 1880 cm was observed, while that derived from CO adsorbed on Pd atoms at 1941 cm is completely absent, which proved that the Pd-core has been completely covered by a Pt-shell. Recently we also characterized Au-core/Pd-shell bimetallic nanoparticles by the CO-IR [144]. Reduction of two different precious metal ions by refluxing in ethanol/ water in the presence of poly(A-vinyl-2-pyrrolidone) (PVP) gave a colloidal dispersion of core/shell structured bimetallic nanoparticles. In the case of Pd and Au ions, the bimetallic nanoparticles with a Au-core/Pd-shell structure are usually produced. In contrast, it is difficult to prepare bimetallic nanoparticles with the inverted core/shell, i.e., Pd-core/Au-shell structure. A sacrificial hydrogen strategy is useful to construct the inverted core/shell structure, where the colloidal dispersions of Pd cores are treated with hydrogen and then the solution of the second element, Au ions, is slowly... 

Polysilane-based nanostructured composites were synthesized by the inclusion of poly(di-w-hexylsilane) (Mw = 53,600) into mesoporous, Si-OH-rich silica with a pore size of 2.8 nm.81 Two PL bands are observed for the composite. A narrow band at 371 nm, assigned to a PDHS film on a quartz substrate is blue shifted by 20 nm, a shift attributed to the polymer being incorporated into the pores.82 The size of the monomeric unit of the PDHS is about 1.6 nm, so only one polymer chain can be incorporated into a mesopore with a diameter of 2.8 nm. The narrow PL band at 350 nm is due to the reduction of the intermolecular interactions between polymer chains. This narrow PL band at 350 nm is assigned to the excited state of the linear polymer chain.81 Also, a new broad band of visible fluorescence at 410 nm appeared, which is assigned to localized states induced by conformational changes of the polymer chains caused by its interaction with the silanol (Si-OH) covered pore surface. Visible luminescence in nanosize PDHS is observed only when the polymer was incorporated in hexagonal pores of 2.8 nm and is not seen for the polymer incorporated into cubic pores of 2.8 nm diameter or hexagonal pores of 5.8 nm diameter. 

The MALDI-TOF spectrum of [G-3] poly(benzyl ether) dendrimer-po-ly(ethylene glycol) triblock copolymer shows a broad band of peaks between 4300 and 6100 D with resolution of the individual ethyleneoxide (44 D) units. The MALDI-TOF spectrum of a [G-3] dendrimer with two polystyrene blocks (molecular peak=8073 D) shows material with 6000-11,000 D and a broad band corresponding to material with 2 M+Ag+. SEC can be used to prove that the latter species is indeed an artifact of the mass spectroscopic method. The authors claim almost exact agreement between the polydispersities derived from MALDI-TOF and SEC [40]. This does, however, not leave any room for the unavoidable column spreading in the latter method. Furthermore, anionically prepared low MW polymers have a minimum polydispersity given by (1 + 1/DP) [41]. 

The NMR spectra of poly-DSP and poly-P2VB show a broad band at r 4.9-5.0 (4H) which is characteristic of protons bonded to a 1,2,3,4-tetraarylated cydobutane ring, and quantitative considerations are consistent with this assignment. 

One- and two-dimensional gel electrophoresis (ID- or 2D-GE) is an important tool in the separation and isolation of intact proteins [9], In ID-GE, the proteins are separated in a sodium dodecylsulfate poly(acrylamide) gel (SDS-PAGE). The separation is according to molecular weight. In 2D-GE, the proteins are first separated by isoelectric point (pi, isoelectric focussing, lEF), and next by molecular weight. 2D-GE is considered to be the most powerful tool in protein separation. Nevertheless, the technique suffers from problems it is labour-intensive, analysis time is long, and the reproducibility poor. Furthermore, hydrophobic proteins do not behave well in the first lEF step and tend to form broad bands. 

The PL spectrum of a thin film of poly(3,6-dibenzosilole) 31 at 77 K exhibited a 0-0 transition at 3.5 eV and a second maximum at 3.3 eV (excitation at 4.4 eV) [41]. The phosphorescence emission spectrum at 77K consists of a broad band exhibiting vibronic structure (excitation at 3.9 eV). The polymer triplet energy level was taken to be the onset of triplet emission at 2.55 eV. This is considerably higher than the triplet energy of commonly used polyfluorenes (2.1 eV) [10,46] making it a host for phosphorescent emitters without the risk of energy back-transfer onto the polymer. 

In order to co-polymerize the IC unit, Suzuki and Stille polymerizations have been used. First, Blouin et al. [94] were able to obtain polyindolo[3,2-fr]-carbazole derivatives with bithiophene or biEDOT as co-monomers. Unfortunately, these studies demonstrated a relatively low oxidation potential for these polymers (especially for P35 and P37), limiting their applications in OFETs and PCs. However, for doped state applications, these polymers may exhibit interesting properties [35]. For instance, when copolymerized with bithiophene, the resulting copolymer shows a good electrical conductivity (as high as 0.7 Scm 1) but a low Seebeck coefficient of 4.3 iV K 1 [35]. Finally, the UV-Vis absorption maxima are similar for poly(2,8-indolocarbazole-a/f-bithiophene) and poly(2,8-indolocarbazole-a/f-bis(3,4-ethylenedioxythiophene)). A broad absorption band is centered at 430 nm whereas, for the 3- and 9-substituted copolymers, the broad band is centered around 490-500 nm [94],... 

On the other hand, a broad band develops at 1200 cm for sulfate contents above 2.5 wt%, and the Vs-o band centered at 1022 cm broadens. A band near 1200 cm has been ascribed by Morterra et al [11] to complex poly-sulfate species, typically observed in samples with sulfate in excess of a monolayer. Olindo et aL [12] also observed a band at this frequency for an amorphous Al-promoted SZ catalyst with 9 mol% AI2O3, and a surface coverage less than a monolayer, which was merely attributed to sulfate groups with a strong reciprocal perturbation owing to the disordered (amorphous) nature of the precursor system. In this study, there is a parallelism between the band at 1200 cm and the overlayer sulfate (sulfate characterized by a DTG minimum near 720°C). 

Two-dimensional (2D) NMR spectroscopy has recently been used to make absolute tacticity assignments without any other supports.195-208 An early successful example is H COSY analysis of poly(vinyl alcohol).198,199 Figure 17 shows a broad-band decoupled H COSY spectrum of poly (vinyl alcohol)199 and illustrative assignments for the correlations between triad peaks of methine proton and tetrad peaks of methylene protons. Expected connectivities between triad and tetrad are as follows ... 

Figure 28 shows the UV—visible spectra of monomer 72. poly-76, and copolymers 77—80. The monomer spectrum was taken in CHCI3. and the polymer spectra were taken in spin-coated films on a quartz substrate. Compound 75 shows the characteristic broad band at 540 nm due to the tt—jt electronic transition of the conjugated cyclic polyene backbone. Copolymers 77—82 containing a chromophore show two maximum absorption values around 390 and 550 nm due to a pendant chromophore and conjugated cyclic polyene backbone, respectively. 

Poly-L-proline exists in two different conformations form I, which assumes a right-handed helix and has each peptide bond in the cis configuration (Traub and Shmueli, 1963) and form II, which is a left-handed helix and has its peptide bonds in the trans configuration (Sasisekharan, 1959 Cowan and McGavin, 1955). Isemura et at. (1968) have differentiated these two forms of poly-L-proline by characteristic far-infrared bands. Form I has two broad bands near 280 and 160cm" and form II... 

Study of the low-frequeney Raman spectrum of poly-L-lysine on both sides of the helix-to-eoil transition using ultrafast spectroseopy reveals the existenee of a broad band that ean be assigned to HB stretching vibrations between the solvent and the peptide. This band is found to shift depending upon the loeal stmeture of the peptide and refleets ehanges in the strength of the interaetions between water and the biopolymer. The frequeney of the band shows that these dynamies oeeur on the seale of 15-30 ps. 

Tsuwi, Appelhans, D., Zchoche, S., Friedel R, and Kremer, E 2004. Molecular dynamics in poly(ethene-aZf-N-alkylmaleimide)s as studied by broad band dielectric spectroscopy. Macromolecules 37 6050-6054. 

Low Frequency Observations for Amorphous Polymers. Many amorphous materials studied by Raman exhibit an extremely broad band in the low frequency region. This is true for polycarbonate, poly(methyl methacrylate), and polystyrene (58). Low frequency Raman bands can potentially provide much information regarding the density of states (directly related to the intensity distribution of the broad Raman active band) as well as anomalous behavior observed for the specific heat (58). Often the separation of main-chain and side-chain bands is important in modeling of specific heat, making careful band assignment extremely meaningful (136,137). This separation is analogous to inclusion of optical... 

The absorption spectrum of Bu4N+-doped poly(p-phenylene) can now be explained as follows. Two broad bands centered at about 5600 and 19400 cm (Figure 4-6) are attributable to the a>i and 0J2 transitions of negative polarons, respectively. These assignments will be discussed again in Section 4.7.3 on the basis of the Raman results. 

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