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Copper(I) Bromide/N-(n-Octyl)-2-pyridylmethanimine−Mediated Living-Radical Polymerization of Methyl Methacrylate Using Carbosilane Dendritic Initiators

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journal contribution
posted on 12.05.2000, 00:00 by Neldes J. Hovestad, Gerard van Koten, Stefan A. F. Bon, David M. Haddleton
The zeroth (Si{(CH2)3SiMe2(C6H4CH2OC(O)CMe2Br)}4), 2, and first (Si{(CH2)3Si((CH2)3SiMe2(C6H4CH2OC(O)CMe2Br))3}4), 3, generation of 2-bromoisobutyryl functionalized carbosilane dendrimers have been successfully applied as initiators for the copper(I) bromide/N-(n-octyl)-2-pyridylmethanimine-mediated living-radical polymerization of methyl methacrylate. The overall rate of polymerization are comparable for the two dendritic initiators studied, 2 (3.4 × 10-5 mol L-1 s-1) and 3 (4.8 × 10-5 mol L-1 s-1) with the benzylic model compound C6H5CH2OC(O)CMe2Br (1) showing a lower rate of polymerization for both dendritic initiators, (7.3 × 10-5 mol L-1 s-1) where [initiator sites] = 1.87 × 10-2 mol L-1. We postulate that this is caused by initial intramolecular termination. The molecular weight distribution is less than 1.3 after 3 h reaction time. Initiator 3, however, produces star−star coupling throughout the polymerization. When the dendritic periphery is partialy functionalized (statistically two and six arms of the first generation dendrimer, respectively, 4 and 5) the control of the molecular weight distribution was lost (PDI > 3) for 4 as a result of too low of a value for [initiator site], i.e., 3.12 × 10-3 mol L-1.