Butadiene viscosity measurements

Research grade poly(styrene-b-butadiene-b-styrene), designated as TR-41-1647, TR-41-1648, and TR-41-1649, were received from Shell Development Co. These block copolymers contain 26.8, 29.3, and 48.2 wt% polystyrene (PS), respectively. The average molecular weights, determined by intrinsic viscosity measurements in toluene at 30°C, were found to be 7-36-6, 16-78-16, and 14-30-14 in units of thousands. The microstructure of polybutadiene (PB) blocks was found to contain about 40 mol% in cis-1,4, 50% in trans-1,4, and 10% in 1,2 units. 

Oxidative degradation by splitting off the double bonds in the butadiene blocks allows the styrene blocks to be isolated. The degradation of the chains can be followed by molecular weight determinations or viscosity measurements (see Examples 3.47, 5.12, 5.14, and 5.15). 

Depending on the concentration, the solvent, and the shear rate of measurement, concentrated polymer solutions may give wide ranges of viscosity and appear to be Newtonian or non-Newtonian. This is illustrated in Eigure 10, where solutions of a styrene—butadiene—styrene block copolymer are Newtonian and viscous at low shear rates, but become shear thinning at high shear rates, dropping to relatively low viscosities beyond 10 (42). The... 

The intrinsic viscosity data on styrene (S)-butadiene (B) block copolymer measured by Utracki and co-workers (4) are replotted in... 

Ono and Ware"" have measured the absorption, emission, and excitation spectra, the fluorescence decay times, and the quantum yields of a series of substituted diphenylmethylenes in rigid matrices at low temperatures. Acean-thrylene shows S2- So emission in hexane with a yield of 0.017 and lifetime of 4.3 ns. The low-temperature fluorescence spectra of bis-2-naphthyl-alkanes and their derivatives have been studied. Excimer formation is an activated process. The fluorescence and absorption spectra of 1,1-diphenyl-ethylenes have been analysed in some detail by Gustav and Bolke. " The S — Si transitions in trans isomers of phenylnaphthylethylenes have been assigned by picosecond absorption spectroscopy. Effects of solvent viscosity and the role of conformers in the mechanism of isomerization are elucidated. The production of non-equilibrium conformer concentrations in glassy solutions of diarylethylenes at 77 K due to restrictions imposed by the solid matrix has also been reported. Free jet excitation and emission spectra of diphenyl-butadiene show clearly the lowest excited Ag state and give a lifetime of 52.8 ns for 0-0 excitation.Electric field-induced charges in the optical... 

Hochstrasser and his co-workers on both stilbene and diphenyl-butadiene. Their interpretation is based on measurements carried on the "stiff" diphenylbutadienes, where the phenyls are held rigid by saturated chains of 2-4 carbon atoms linked through the 2 positions of aromatic ring to the double band. The apparent energy barriers and the dependence on viscosity deviate from the Kramer s model but are consistent with the modified Kramers-Hubbard model... 

Aspects of viscosity, elasticity, and morphology have been discussed in general terms by various workers [73-76]. Rheological studies specific to particular polymers include dynamic rheological measurements and capillary rheometry of rubbers [77], capillary rheometry of PP [78], degradation of PP [79], torsion rheometry of PE [80], viscosity effects in blends of PC with styrene-acrylonitrile and acrylonitrile-butadiene-styrene [81], peel adhesion of rubber-based adhesives [82], and the effect of composition of melamine-formaldehyde resins on rheological properties [83]. 

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