Ring‐opening metathesis polymerization (ROMP) of norbornene in supercritical carbon dioxide using well‐defined metal carbene catalysts

Ring‐opening metathesis polymerization (ROMP) of bicyclo[2,2,1]hept‐2‐ene (norbornene) has been effected in supercritical carbon dioxide (SC CO2) with two types of metal carbene catalysts. It has been found that the polynorbornenes prepared in SC CO2 are similar in molecular weight, molecular weight distribution and thermal stability to their counterparts prepared in tetrahydrofuran (THF). More important, the trans/cis ratio of the resulting polymers could be adjusted by varying the amount of cosolvent THF or metal carbene catalysts. However, neither the reaction temperature nor pressure significantly influenced the trans/cis ratio of the polymer.