EXPLORING FACTORS THAT DETERMINE CIS TRANS STRUCTURE AND TACTICITY INPOLYMERS PREPARED BY RING-OPENING METATHESIS POLYMERIZATION WITH INITIATORS OF THE TYPE SYN-MO(NAR)(CHCME(2)PH)(OR)(2) AND ANTI-MO(NAR)(CHCME(2)PH)(OR)(2) - OBSERVATION OF A TEMPERATURE-DEPENDENT CIS/TRANS RATIO/

The factors that determine the structure (cis/trans and tacticity) of polymers prepared by ring-opening metathesis polymerization (ROMP) fro m 2,3-bis(trifluoromethyl)norbornadiene (NBDF6) and several bis(carboa lkoxy)norbornadienes using well-defined initiators of the type Mo(NAry l)(CHCMe(2)-Ph)(OR)(2) (Aryl = a substituted aryl group and OR = a var iety of alkoxides) have been explored. The main finding is a dependenc e of cis/trans structure on temperature; at low temperatures (-35 degr ees C) all-cis polymer is formed and at high temperatures (65 degrees C) up to 90% trans polymers are formed. These results are consistent w ith formation of cis polymer from syn alkylidene rotamers and trans po lymer from anti alkylidene rotamers in circumstances where syn and ant i rotamers can interconvert. Several all-cis polymers prepared from ac hiral initiators that contain various fluorinated alkoxides were found to be biased toward isotacticity. In one case, however, the polymer w as biased toward syndiotacticity.