Polymeric liquids mechanical spectrum

Figure 3.10 Predictions of the temporary network model [Eq. (3-24)] (lines) compared to experimental data (symbols) for start-up of uniaxial extension of Melt 1, a long-chain branched polyethylene, using a relaxation spectrum fit to linear viscoelastic data for this melt. (From Bird et al. Dynamics of Polymeric Liquids. Vol. 1 Fluid Mechanics, Copyright 1987. Reprinted by permission of John Wiley Sons, Inc.)...

FIGURE 11.3 Typical mechanical spectrum of a polymeric liquid. Shadow region corresponds to the most frequently observed one. 

Japanese investigators reported that liquid sulfur dioxide polymerizes styrene derivatives (e.g., p-methyl styrene, a-methyl styrene) (19). Unfortunately, the experiments were not executed under rigorously anhydrous conditions (high vacuum) so that the possibility for proton (e.g., sulfurous or sulfuric acid) initiation exists although the authors seem to believe that S02 is the catalyst, probably by the following process 2S0a SO2 +SO e. The cationic nature of the mechanisms was proven by the facts that no polysulfones formed, that the polymerization was inhibited by bases, and that free radical inhibitors did not affect the reaction. These authors also claim that formaldehyde is polymerized by sulfur dioxide to a product which does not contain sulfur and whose infrared spectrum closely resembles that of a low temperature sample. 

The products resulting from replacement of aromatic H by CH3, in the vapor-phase radiolyses of the alkylbenzenes, show a strong preference for meta orientation. That these products are derived from radicals is suggested by our observation that no xylenes are formed when toluene vapor is radiolyzed in the presence of iodine. The distribution of isomers does not, however, correspond to the preferential ortho substitution found (16) in the homolytic methylation of toluene, nor does it resemble the nearly statistical distribution observed in liquid phase radiolysis or in vapor-phase photolysis at 2537 A. (17). The process is obviously complex, and there is little direct evidence on which to base a mechanism. It may, nevertheless, be of interest that the C8H9+ ion is observed (15) in the mass spectrum of toluene at moderate pressures. Neutralization of such an ion could lead to radicals and ultimately to aromatic products. It is also of interest that the high pressure mass spectrum shows (15) abundant formation of dimeric ions, which may well be involved in the enhanced production of dimer and higher polymeric products in the vapor phase radiolysis. 

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