Copolymerization of Norbornene and Norbornadiene Using a cis-Selective Bimetallic W-Based Catalytic System
1
Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, Athens 15771, Greece
2
National Institute of Chemistry, Ljubljana 1000, Slovenia
3
Istituto Italiano di Technologia, 16163 Genova, Italy
4
Organic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, Athens 15771, Greece
5
Industrial Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, Athens 15771, Greece
*
Author to whom correspondence should be addressed.
Academic Editor: Changle Chen
Polymers 2017, 9(4), 141; https://doi.org/10.3390/polym9040141
Received: 14 March 2017 / Revised: 7 April 2017 / Accepted: 10 April 2017 / Published: 18 April 2017
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
The bimetallic cluster Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 ({W2}, {W 3 W}6+, a′2e′4), which features a triple metal-metal bond, is a highly efficient room-temperature initiator for ring opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene (NBD), providing high-cis polymers. In this work, {W2} was used for the copolymerization of the aforementioned monomers, yielding statistical poly(norbornene)/poly(norbornadiene) PNBE/PNBD copolymers of high molecular weight and high-cis content. The composition of the polymer chain was estimated by 13C CPMAS NMR data and it was found that the ratio of PNBE/PNBD segments in the polymer chain was relative to the monomer molar ratio in the reaction mixture. The thermal properties of all copolymers were similar, resembled the properties of PNBD homopolymer and indicated a high degree of cross-linking. The morphology of all materials in this study was smooth and non-porous; copolymers with higher PNBE content featured a corrugated morphology. Glass transition temperatures were lower for the copolymers than for the homopolymers, providing a strong indication that those materials featured a branched-shaped structure. This conclusion was further supported by viscosity measurements of copolymers solutions in THF. The molecular structure of those materials can be controlled, potentially leading to well-defined star polymers via the “core-first” synthesis method. Therefore, {W2} is not only a cost-efficient, practical, highly active, and cis-stereoselective ROMP-initiator, but it can also be used for the synthesis of more complex macromolecular structures.
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Keywords:
copolymerization; metathesis; norbornene; norbornadiene; ROMP; metal-metal bonds; star polymers; tungsten; viscometry
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MDPI and ACS Style
Raptopoulos, G.; Kyriakou, K.; Mali, G.; Scarpellini, A.; Anyfantis, G.C.; Mavromoustakos, T.; Pitsikalis, M.; Paraskevopoulou, P. Copolymerization of Norbornene and Norbornadiene Using a cis-Selective Bimetallic W-Based Catalytic System. Polymers 2017, 9, 141.
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