Molecular characterization of poly(2-phenyl-1,3-butadiene) prepared by anionic living polymerization.

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2-Phenyl-1, 3-butadiene (2PB) was anionically polymerized to give the polymers having high molecular weights and narrow molecular weight destributions. The microstructures of the polymers were primarily dependent on the polymerization temperature, irrespective of the varieties of polymerization solvents. Taking into account the microstructures, it is concluded that 1, 4-additions proceed selectively in the propagation of 2PB. This conclusion is supported by the calculated values of frontier electron density of the monomer. The characteristic ratio, C∞, of poly (2PB) containing 92% 1, 4-E structure was estimated to be 6.9 from the intrinsic viscosity measurement at near Θ temperature (65°C in n-butyl formate). The glass transition temperature was 28°C. Furthermore, the pseudo-equilibrium shear modulus, G0eN, evaluated from the measurement of stress relaxation was 1.26×106dyn/cm2 (log G0eN=6.10), from which the entanglement molecular weight, Me, was estimated to be 2.1×104. These results show that the bulky substituent, phenyl group, exerts enormous effects on the nature of the polymer, such as chain rigidity, free volume, and dynamic interactions.
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