Neodymium alk(aryl)oxides-dialkylmagnesium systems for butadiene polymerization and copolymerization with styrene and glycidyl methacrylate

The application of well-defined neodymium. alkoxides/aryloxides in combination with dialkylmagnesium reagents for 1,3-butadiene (1313) polymerization and copolymerization with styrene (St) and glycidyl methacrylate (GMA) has been investigated. The trinuclear complex Nd-3(Ot-Bu)(9)(THF)(2) (1) provided a low-activity system for BD polymerization, even at high temperature, but with a high trans-1,4 stereospecificity (trans-1,4 approximate to 95%). Aryloxide complexes Nd(O-2,6-t-Bu-2-4-Me-Ph)(3)(THF) (2) and Nd(O-2,6-t-Bu-2-4-Me-Ph)(3) (3) were found to give more active systems. The polymerization displayed a controlled character, i.e. a precise control of the molecular weight and a low polydispersity (M-w/M-n < 1.30) for high catalyst concentration, keeping the same level of stereocontrol over the polymerization course. The statistical copolymerization of BD and styrene with those systems was successful. High-molecular weight copolymers (M-n up to 50 000 g mol(-1)) with noticeable styrene content (3-15 mol%) were synthesized. Determination of the microstructure by C-13-NMR showed exclusively trans-1,4-BD-St sequences. The livingness of BD polymerization encouraged attempts of diblock copolymerization with GMA. In this case, low-molecular weight polymers with variable polydispersities were obtained (M-n < 20 000 g mol(-1); M-w/M-n = 1.4-5.0). The composition of the copolymers was analyzed by H-1- and C-13-NMR and IR spectroscopies. SEC analyses confirmed the true nature of the diblock copolymer. The influence of the alkylating agent on those (co)-polymerizations was briefly studied. Finally, the mechanism of polymerization is also discussed. (C) 2003 Elsevier Science B.V. All rights reserved.