Cationic polymerization of α-methylstyrene in dichloromethane initiated with system 2,5-dichloro-2,5-dimethylhexane-BCl3. I. Molecular weight distribution and stereoregularity of poly (α-methylstyrene) |
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Authors: | L Toman S Pokorný J Spv
ek |
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Institution: | L. Toman,S. Pokorný,J. Spěváček |
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Abstract: | In the polymerization of α-methylstyrene (α-MeSt) in dichloromethane in the temperature interval between ?60 and ?20°C the polymer yield decreased with increasing temperature depending on the initiating system used (I-IV) in the series II > I > IV > III, where I was a freshly prepared solution of 2,5-dichloro-2,5-dimethylhexane (DDH) with BCl3 in dichloromethane, was the same solution as in the preceding case, but stored at room temperature one month and then used, III was a freshly prepared BCl3 solution in dichloromethane, and IV was the initiation system “H2O”/BCl3. The polymer samples synthesized at ≤ ?30°C had a bimodal molecular weight distribution (MWD), which was attributed to the different participation of ionic pairs and free ions in the propagation reaction. The stereoregularity of the polymer observed (ca. 85% syndiotactic and ca. 15% heterotactic triads) determined from the 1H-NMR spectra was not affected by the difference in the initiation system. MWD of the polymer samples was investigated by the GPC method |
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