Synthesis and rheological properties of poly(5-n-hexylnorbornene)

Poly(5-n-hexylnorbornene) (PHNB) was obtained in high molecular weight and high yields by vinyl-type polymerization of 5-n-hexyl-2-norbornene (endo/exo = 77/23) with [NiBr(NPMe3)](4)/B(C6F5)(3) as catalyst precursor. The combination of size exclusion chromatography with online light scattering and intrinsic viscosity measurements allowed the Mark-Houwink expressions to be evaluated in tetrahydrofuran. The unperturbed chain dimensions for poly(5-n-hexylnorbornene) were estimated via the extrapolation procedure of Burchard-Stockmayer-Fixman. This evaluation of the unperturbed chain dimension in turn permits the calculation of the entanglement molecular weight and the plateau modulus via the packing length model. This allows the determination of rheological properties for these materials where conventional rheology measurements are difficult, or impossible.