The synthesis of cyclic olefin copolymers (COCs) by ethylene copolymerisations with cyclooctene, cycloheptene, and with tricyclo[6.2.1.0(2,7)]undeca-4-ene: the effects of cyclic monomer structures on thermal properties

Abstract

Ethylene copolymerisations with cyclooctene (COE) by half-titanocenes, Cp′TiCl₂(X) [X = OAr (Ar = 2,6-ⁱPr₂C₆H₃), Cp′ = 1,2,4-Me₃C₅H₂, ^tBuC₅H₄, C₅Me₅ (Cp*), indenyl; X = NC^tBu₂, Cp′ = Cp, ^tBuC₅H₄, indenyl] and [Me₂Si(C₅Me₄)(NR)]TiCl₂ [R = ^tBu (CGC), cyclohexyl], and by metallocenes, Cp₂ZrCl₂ and [Me₂Si(indenyl)₂]ZrCl₂ (SBI), have been explored. Cp*TiCl₂(OAr) afforded high molecular weight amorphous copolymers with efficient COE incorporation as well as exclusive 1,2-insertion (M_n = 1.08–12.6 × 10⁵), whereas CGC and SBI afforded semi-crystalline copolymers with less COE incorporation. Copolymerisation with cycloheptene gave ultrahigh molecular weight amorphous copolymers (M_n = 1.32–3.08 × 10⁶). Linear relationships between the glass transition temperatures (T_g) and cyclic olefin contents have been demonstrated, and the T_g values were affected by the ring size. Copolymerisation with tricyclo[6.2.1.0(2,7)]undeca-4-ene by CpTiCl₂(NC^tBu₂) afforded high molecular weight copolymers, with high T_g values by the introduction of an additional cyclic unit.