Solvent effect in the polymerization of e-caprolactone initiated with diethylaluminum ethoxide

✍ Scribed by Tadeusz Biela; Andrzej Duda

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 514 KB
• Volume: 34
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19960715)34:9<1807::aid-pola19>3.0.co;2-a

✦ Synopsis

Kinetics of t-caprolactone (tCL) polymerization initiated with diethylaluminum ethoxide in benzene (C6H6) and acetonitrile (CH3CN) as solvents was studied and compared with the previously studied polymerization conducted in tetrahydrofuran (THF) solvent. Kinetic data were analyzed in terms of the kinetic scheme: "propagation with aggregation," assuming that actually propagating active species (P:) aggregate reversibly into the unreactive (dormant) species (P:), C mP:, P: + cCL -P P:+l. The determined equilibrium constants of deaggregation (Kda) decrease with decreasing solvent polarity, namely &, (in mo12 -L-') = (1.3 k 0.7) + lo-* (CH,CN), (1.8 (C6H6), whereas for the rate constants of propagation the opposite is true, kp(in mol-' -L * s-') = (7.5 f 0.3) -(CH,CN), (3.87 f 0.01) + lo-' (THF), (8.6 k 0.9)lo-' (C6H6) (25°C). The latter effect is explained by a specific solvation (the stronger the higher solvent polarity) of the active species already in the ground state in the elementary reaction of the poly(tCL) chain growth:

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