Polybutadiene - continued molecular weight

We can test our predictions for the scaling correction S(N) to the zero-shear viscosity by comparing them against experimental data. In Fig. U we have plotted experimental values of the zero-shear viscosity of polybutadiene versus molecular weight as reported by Colby, Fetters and Graessley. The continuous curve in this figure was computed from Eqs.(43) and (33) using the polymer data in Table 1. The viscosity values were divided by to remove the pure reptation component. Therefore any non-zero slope in Fig. 4 represents a departure from reptation theory which corresponds to the function S(N) in Eq. (44). 

To improve the processibility of linear polybutadiene with its narrow molecular weight distribution, one can continuously add initiator in the course of the polymerization, vary the reaction temperature, or force long-chain branching by addition of divinyl compounds [68-74]. Addition of small amounts of ethers or tertiary amines alters the vinyl content from some 12% to more than 70% (Table 2). Bis(2-methoxy)ethyl ether and l,2-bis(dimethylamino)ethane as well as crown ethers [75,76] are particularly effective. The microstructures of the products are determinated by IR [77-87], NMR [88-99], x-ray diffraction, and other methods [100,101]. 

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