Cycloaliphatic Polymers via Late Transition Metal Catalysis - Late Transition Metal Polymerization Catalysis - page 112

Fig. 4.9 (a) 13 C NMR spectrum
of poly(norbornene) made with
naked nickel, (b) 13 C NMR spec-
trum of poly(norbornene) made
with naked palladium.

type. This pattern persists in other regions of the 2D spectrum. For the polymer
backbone carbons 2 and 3, which appear the farthest downfield in the 13 C NMR
spectrum, there are two rather strong crosspeaks at about 49.5 and 50.5 ppm in
the nickel-based polymer. In the palladium-based polymer only one strong cross-
peak appears in this region at around 53 ppm. From this analysis, the palladium
polymer microstructure is clearly more regular than the nickel poly(norbornene).
Prior to these studies the first indication of major architectural differences between
the nickel- and palladium-catalyzed poly(norbornene)s was in their grossly different
solubility behavior. The nickel-based poly(norbornene) is highly soluble in simple
hydrocarbons such as heptane and cyclohexane at room temperature even at very
high molecular weights (>1000000). Using the palladium catalysts, it was observed
that the poly(norbornene)s generated are insoluble in simple hydrocarbons but, at
lower molecular weights, can be coaxed into solution using hot o -dichlorobenzene.
This remarkable difference in solubility characteristics shows that there is clearly
a large difference in polymer architecture between the nickel- and palladium-derived
polymers, necessitating the isolation and characterization of poly(norbornene) oligo-
mers to fully elucidate the microstructure (see Section 4.2.3.7).

4.2.3.6 On the Mechanism of Propagation and Chain Transfer
In the course of our polymerization studies the performance of these new cata-
lysts in the copolymerization of norbornenes with -olefins such as ethylene, 1-

hexene and 1-decene was investigated. The primary reason for exploring this area
was to enable copolymerization of norbornenes with ethylene (and other

-olefins)