A kinetic investigation of the mechanism of vinyl polymerizations initiated by bis-acetylacetonato-iron(II)—I: Styrene and vinyl acetate

✍ Scribed by P.E.M. Allen; T.H. Goh

• Publisher: Elsevier Science
• Year: 1969
• Tongue: English
• Weight: 351 KB
• Volume: 5
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(69)90138-4

✦ Synopsis

Abstraet--Bis-acetylacetonato-iron(ID initiates a slow radical polymerization of styrene in bulk above 40 ° . The order of reaction with respect to initiator is low and decreases to zero as the initiator concentration increases. The overall rate of polymerization obeys the Arrhenius equation in the zero-order region. The mechanism proposed involves a termination reaction between the propagating radical and the initiating complex or some species closely related to it.

Bis-acetylacetonato-iron(II) does not polymerize vinyl acetate at 60 °. No reaction of any kind could be detected, confirming that the initiator is selective and that initiation in the case of styrene and methyl methacrylate is the result of specific interactions between monomer and initiator.

THERE have been a number of reports that acetylacetonato complexes of the higher oxidation states of transition metals, e.g.: Mnm(Acac)3, (1' 2) Com(Acac)3,(l. 3.4) CeIV(Acac)4, as well as bis-ethylacetoacetate-Cu", (s) initiate radical polymerization. On the other hand complexes of the lower oxidation states were believed to be inactive, or, at the most, only active at very higher temperature. (1) Burnett and North (6) reported that at 40 ° the polymerization of styrene in the presence of an unspecified concentration of Fe"Acacz was slightly slower than the spontaneous, "thermally" initiated polymerization of unadulterated styrene. Experiments reported in the present paper confirm the observation that FenAca~2 is not an effective initiator at 40 °. However above 50 ° the rates of polymerization in the presence of the complex are significantly in excess of the "thermal" rates.