The synthesis of cyclic olefin copolymers (COCs) by ethylene copolymerisations with cyclooctene, cycloheptene, and with tricyclo[126.96.36.199(2,7)]undeca-4-ene: the effects of cyclic monomer structures on thermal properties†
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 = NCtBu2, 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 (Mn = 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 (Mn = 1.32–3.08 × 106). Linear relationships between the glass transition temperatures (Tg) and cyclic olefin contents have been demonstrated, and the Tg values were affected by the ring size. Copolymerisation with tricyclo[188.8.131.52(2,7)]undeca-4-ene by CpTiCl2(NCtBu2) afforded high molecular weight copolymers, with high Tg values by the introduction of an additional cyclic unit.