Copolymerization of ethylene with cyclopentene or 2‐butene with half titanocenes‐based catalysts |
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Authors: | Mariagrazia Napoli Annaluisa Mariconda Ivano Immediata Pasquale Longo |
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Institution: | Dipartimento di Chimica, Università di Salerno, Via Ponte don Melillo, 84084 Fisciano (SA), Italy |
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Abstract: | Half titanocenes (CpCH2CH2O)TiCl2 (1), (CpCH2CH2OCH3)TiCl3 (2), and CpTiCl3 (3), activated by methylaluminoxane (MAO) were tested in copolymerization of ethylene with internal olefins such as cyclopentene. All the catalysts were able to give incorporation of cyclopentene in polyethylene matrix. 13C NMR analysis of obtained copolymers showed that the catalytic systems have low regiospecificity. In fact, in ethylene–cyclopentene copolymers, cyclic olefin inserts with both 1,2 and 1,3‐enchainment. X‐ray powder diffraction analysis of these copolymers confirmed that 1,2 inserted cyclopentene units are excluded from crystalline phase, whereas 1,3‐cyclopentene units are included, giving rise to expansion of unit cell of crystalline polyethylene. Titanium‐based catalysts were investigated also in the copolymerization of ethylene with E and Z‐2‐butene. Only complex (1) was able to give copolymers and 13C NMR analysis of products showed 2‐3, 1‐3, and 1‐2 insertion of 2‐butene. Differential scanning calorimetry analysis displayed that ethylene–cyclopentene, as well as ethylene‐2‐butene, copolymers are crystalline and their melting point decreases by increasing the comonomer content. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4725–4733, 2008 |
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Keywords: | copolymerization cyclopentene differential scanning calorimetry (DSC) ethylene half‐titanocene metallocene catalysts NMR polyolefins 2‐butene |
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