Vinyl addition polymerization behavior of poly(5-hexyl-2-norbornene-co-5-methylester-2-norbornene)s using cationic eta(3)-allyl palladium catalyst

Abstract

We synthesized the vinyl addition-type polynorbornene copolymers using two monomers [5-hexyl-2-norbornene (HNB) and 5-methylester-2-norbornene(MES-NB)] by means of a cationic eta(3)-allyl palladium catalyst system {[(eta(3)-allyl)palladium(tricyclohexylphosphine) tifluoroacetate] and [lithium tetrakis(pentafluorophenyl) borate (.) 2.5etherate] }. The molecular weights and yields of copolynorbornenes polymerized in various conditions were measured to investigate an optimum polymerization conditions to obtain highly es ter-functionalized polynorbornenes. As a Pd catalyst content increased, the molecular weights (Mw) of polymers decreased while polymer yields increased. Also, as a Li cocatalyst content increased, the Mw's and yields of polymers increased at the same time. The Mw's of copolymers were also controlled by chain transfer agents such as 1-hexene, 1-octene and 1-decene, and we found that longer 1-decene and 1-octene were more efficient to reduce the Mw's of polynorbornenes than 1 hexene. On the other hand, the content of chain transfer agents did not give influence significantly on polymer yields. From the H-1-NMR and GPC analysis of HNB/MES-NB (feed ratio of 40/60 mol%) copolymer, we found that this copolymer had an about 25 mol% of ester portion and a high molecular weight of 270,000.