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Polybutadiene stars

Pryke, A. et al. Synthesis, hydrogenation, and rheology of 1,2-polybutadiene star polymers. Macromolecules, 35, 467, 2002. [Pg.218]

Consider a polystyrene-( )-polybutadiene star block copolymer with four arms coupled by a central Si-atom. Or consider a metal catalyst (e.g., Au) supported in activated carbon. Then the scattering of only the selected element (Si, Au, respectively) can be extracted [242], Even the distribution of the elements in the material can be mapped based on ASAXS data. A concise review of the ASAXS method in combination with AXRD and AWAXS has been published by Goerigk et al. [243]. [Pg.203]

In comparison to the polybutadiene stars under similar reaction conditions, the polyisoprene stars showed slightly lower degrees of branching. The added steric hindrance from the methyl group on the polyisoprene anion perhaps makes entry into the DVB "microgel" nodule difficult. [Pg.576]

Although the model studies indicated that selectivity of sulfonation was considerably less than desired, it was decided to proceed with the synthesis of the polyisoprene/polybutadiene star-block copolymer, anyway. It was felt that selectivity was good enough so that an appreciable fraction of the isoprene units could be sulfonated while limiting sulfonation of the butadiene units to some negligible level. For example, the data in Table II indicates that at 21 C, with a 1 1 mole ratio of sulfonating reagent, one should obtain about 50% sulfonation of the isoprene units with virtually no sulfonation of the butadiene units. This was deemed acceptable since the number of isoprene units at the chain ends could be simply doubled, and... [Pg.337]

Figure 12. FT-IR spectra of unsaturated and hydrogenated polystyrene/polybutadiene star-block copolymer (SBD-2). Figure 12. FT-IR spectra of unsaturated and hydrogenated polystyrene/polybutadiene star-block copolymer (SBD-2).
Fig. 11 The dynamic structure factor C(, r) of polybutadiene star 12880 (nominally f = 128, Ma = 80kgmol ) in cyclohexane at ci = 0.016gmL and q = 0.035nm , along with the fit (solid line) from the ILT analysis. The corresponding relaxation distribution function L(ln(T)) (shown here for f i and q = 0.023gmL ) embraces the cooperative diffusion (1), the collective apparent diffusion (2), and the self-diffusion (3). The slowing-down of the middle structural mode (2) and the increase of its intensity with q are shown in the upper inset whereas the lower cartoon illustrates the liquid-like ordering [43,189]. The core regions are drawn out of scale (larger) for clarity... Fig. 11 The dynamic structure factor C(, r) of polybutadiene star 12880 (nominally f = 128, Ma = 80kgmol ) in cyclohexane at ci = 0.016gmL and q = 0.035nm , along with the fit (solid line) from the ILT analysis. The corresponding relaxation distribution function L(ln(T)) (shown here for f i and q = 0.023gmL ) embraces the cooperative diffusion (1), the collective apparent diffusion (2), and the self-diffusion (3). The slowing-down of the middle structural mode (2) and the increase of its intensity with q are shown in the upper inset whereas the lower cartoon illustrates the liquid-like ordering [43,189]. The core regions are drawn out of scale (larger) for clarity...
Fig. 19 (a) Intermediate scattering function C(, r) of hard sphere PMMA (7 h = 205 nm) suspension (in cz5-decalin) at qR = 2.68, from the dilute to the glassy regimes (volume fraction (+) 0.494, open circle 0.528, open triangle 0.535, open square 0.558, (x) 0.567, diamond 0.574, solid triangle 0.581, solid circle 0.587). Solid lines represent MCT fits. Taken from [237]. (b) Respective response of a colloidal polybutadiene star suspension (in good solvent cyclohexane, at 20°C) at different values of the effective hydrodynamic volume fraction c/c open circle 0.06, open square 0.72, asterisk 1.02, open triangle 1.48. Taken from [248]... [Pg.35]

The breakthrough in the synthesis of multiarm star polymers was made by Roovers, who reported the high-vacuum anionic synthesis of 1,4-polybutadiene stars via two distinct routes (1) using chlorosilane chemistry, central dendritic cores of spherical shape and different generations were synthesized, to which the desired number of polymeric arms were grafted. With this approach regular stars with typical nominal functionality / in the range 18-128 and nominal... [Pg.323]

Master curves (7b = 25 °C) for the complex viscosity of two nearly monodisperse 1,4-polybutadiene melts [28] are shown in Fig. 3.24. One is linear rjo = 4.8 X 10 Pa s, J° = 2.1 X 10 Pa ), the other a three-arm star rjo = 2.8 x 10 Pa s, J° - 1. 4 X 10 Pa ). Their zero-shear viscosities are similar, but their recoverable compliances differ by a factor of seven and the shapes of their curves are obviously different, too. Figures 3.25(a) and (b) compare those results with steady-shear-viscosity data for nearly monodisperse polymers, showing master curves at 183 °C for five linear polystyrene samples [29] (48 500 < M < 242 000) in Fig. 3.25(a), and master curves at 106 °C for seven polybutadiene stars [30] (45 000 < M < 184000) in Fig. 3.25(b). Values of t]o were available for all samples, so knowledge of rj y)/r o was always available. Values of J° were not generally available, so Tq for the shear-rate reduction was estimated from the onset of shear-rate dependence. Agreement with the Cox-Merz rule is evident even in this rather severe test of using different samples and even different species. The... [Pg.178]

Experimentally, is approximately 0.6. Thus, for branched polymers in the entanglement region, both rjo and may be quite large compared with the values for linear polymers of the same molecular weight. The terminal zone is inherently broader for well-entangled branched polymers than it is for linear polymers of comparable polydispersity [49]. The complex viscosities for a nearly monodisperse linear polybutadiene and three-arm polybutadiene star, shown in Fig. 3.24 for other purposes, exemplify the more gradual transition from Newtonian to power-law... [Pg.203]

Second virial coefficient of polybutadiene (star polymers)... [Pg.699]


See other pages where Polybutadiene stars is mentioned: [Pg.127]    [Pg.175]    [Pg.183]    [Pg.574]    [Pg.108]    [Pg.566]    [Pg.568]    [Pg.285]    [Pg.105]    [Pg.8]    [Pg.10]    [Pg.20]    [Pg.23]    [Pg.27]    [Pg.40]    [Pg.202]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]    [Pg.699]   
See also in sourсe #XX -- [ Pg.105 , Pg.114 ]




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