Hexacyclotetradecenes as Polycyclic Fused exo-Norbornene Monomers: Synthesis of Cyclic Olefin Copolymers via Ti-Catalyzed Controlled Polymerization

17 May 2024, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Polycyclic fused norbornenes (NBs) are important monomers for producing thermally stable cyclic olefin polymers and copolymers (COCs). However, the difficult addition polymerization of sterically demanding endo-substituted NBs limits the range of accessible COCs. Here, we explored the synthesis and polymerization of an isomeric mixture of hexacyclotetradecenes (1a and 1b) as new polycyclic fused exo-NB-based monomers. These monomers were readily prepared via a two-step catalysis process: norbornadiene dimerization followed by protic-acid-catalyzed isomerization. While ring-opening metathesis polymerization using conventional Ru carbene catalysts was not viable, addition polymerization and copolymerization with 1-octene, using a constrained geometry Ti catalyst, successfully proceeded in a controlled manner. Monomer 1 was consumed faster than 1-octene to form gradient copolymers. 13C nuclear magnetic resonance spectroscopies exhibited reasonable signals that indicated a 1,2-addition polymer structure. X-ray diffraction and thermogravimetry analysis confirmed the amorphous nature and thermal stability of poly1, which showed no weight loss below 400 °C. Thus, this study demonstrates the synthesis and polymerization of new promising polycyclic olefin monomers suitable for producing COC materials.

Keywords

cyclic olefin copolymer

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