Polymerization of α-Methylstyrene at High Temperatures in Tetrahydrof uran with Potassium as Initiator. I. Thermodynamic Study and Gel-Permeation Chromatographic Analyses of the Polymers

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Abstract
Polymerization of α-methylstyrene in tetrahydrofuran with potassium as initiator has been studied in the -25 to 60°C temperature range. Variation of the monomer concentration at equilibrium [M]e, with its own polymer [P]e, was found to be linear at 25 and 40°C. The experiments carried out at 50, 55, and 60°C yielded high values of [P]e and polymers with high viscosity. The GPC distributions of these polymers were found to be multimodal in character, yielding four components D, A, B, and C with an average degree of polymerization, DP, of about 4, 16, 250, and 1000, respectively. It was found that the living end concentration, [LE] calculated from the viscosity-average molecular weight Mv differs to a considerable extent from those calculated on the basis of number-average molecular weight, Mn (GPC). In spite of these initial high [LE] values (10−1 and 10−2), component C had [LE] of the order of 10−3 mole/liter associated with it. The formation of high molecular weight-polymer at high temperatures in solution with high [M]0 was found to be the products of slow initiation and rapid propagation at 25°C which did not depropagate when kept at 50 or 60°C although active ends were still present. In solutions with low [M] 0 and high [LE], where initiation was instantaneous, the GPC distributions were also multimodal. It has been speculated that these multimodal distributions are a result of dead and dormant polymers in combination with polymers due to different ion pairs.