Styrene, polymerization, anionic thermodynamics

The first application of living polymers in thermodynamic studies was reported by Worsfold and Bywater181) and by McCormick182). In both studies anionic polymerization of a-methyl styrene, initiated in tetrahydrofuran by electron-transfer, was investigated over temperatures ranging from 0°C to -40°C. The results are shown graphically in Fig. 3, and lead to heat of polymerization of — 8 kcal/mol, entropy of polymerization in solution of 29 eu, and to about 1 M equilibrium concentration of a-methyl styrene at ambient temperature. 

Anionic polymerization was utilized again in studies of thermodynamics of styrene propagation185. The equilibrium concentration of that monomer is exceedingly low at ambient temperature, and hence the experimentation required elevated temperatures. However, living polystyrene in THF is rapidly destroyed at those temperatures. To avoid these difficulties, living polystyrene formed by BuLi initation in cyclohexane or benzene was used in the studies. The results are presented in Fig. 5 and in Table 1. The effect of the solvent s nature on Me is revealed by these data. 

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