EXPLORING FACTORS THAT DETERMINE CIS/TRANS STRUCTURE AND TACTICITY IN POLYMERS 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) from 2,3-bis(trifluoromethyl)norbornadiene (NBDF6) and several bis(carboalkoxy)norbornadienes using well-defined initiators of the type Mo(NAryl)(CHCMe(2)-Ph)(OR)(2) (Aryl = a substituted aryl group and OR = a variety of alkoxides) have been explored. The main finding is a dependence of cis/trans structure on temperature; at low temperatures (-35 degrees C) all-cis polymer is formed and at high temperatures (65 degrees C) up to 90% trans polymers are formed. These results are consistent with formation of cis polymer from syn alkylidene rotamers and trans polymer from anti alkylidene rotamers in circumstances where syn and anti rotamers can interconvert. Several all-cis polymers prepared from achiral initiators that contain various fluorinated alkoxides were found to be biased toward isotacticity. In one case, however, the polymer was biased toward syndiotacticity.