The Effect of endo/exo-Norbornene Isomer Ratio on Poly(norbornene) Optical Density at 193 nm

The polymerization of exo-[(norbornenemethoxy)methyl]-1,1,1,3,3,3-hexafluoro-2-propanol (2) using a palladium catalyst gave a significantly higher Mw polymer than the endo isomer or the 80/20 mixture of endo/exo-2. To achieve similar Mw higher concentrations of formic acid chain transfer agent was needed for the exo isomer than for the 80/20 mixture. As a result, the optical density at 193 nm of the exo isomer polymer is substantially lower since less olefinic polymer end groups were formed. A subtle interplay between chain transfer mechanisms and propagation rates explains the results obtained. Isomer content in poly(2) does not affect the dissolution rate in TMAH.