Effects of microstructures on the viscoelastic and rheological properties of metallocene‐catalyzed cyclo‐olefin copolymers: A preliminary study

We characterized metallocene-catalyzed cyclo-olefin copolymers (mCOCs) with similar heat distortion temperatures but dramatic differences in melt-flow indices to understand how the molecular conformation affected their rheological and viscoelastic properties. The mCOC conformations were identified with 13C-NMR, whereas the viscoelastic and rheological properties were measured with cone-and-plate and high-pressure capillary rheometers. Our preliminary results showed that the mCOC rheological and viscoelastic properties might depend strongly on the conformation rather than the norbornene content, molecular weight, and molecular weight distribution. mCOCs containing -NNN- locks (where N represents norbornene) exhibited stronger molecular entanglements than those having no -NNN- blocks, as reflected in lower crossover frequencies and higher crossover torque. Furthermore, the existence of larger rigid -NNN- blocks resulted in higher molten viscosities and flow activation energies. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3695–3701, 2002