Nickel Polymerization Catalysts with Ylide Steering Ligands - Late Transition Metal Polymerization Catalysis - page 20

Fig. 1.5 PANPAC, model of a novel
matrix polyacetylene.
polymers are polyethylene, polypropylene, polystyrene, polyisoprene, polychloro-
prene, poly(vinyl chloride), polycarbonate, polyvinylpyrrolidone, polyvinylcarbazole,
poly(ethyl acrylate), poly(methyl methacrylate) and methylated cellulose.
Some of the innovative materials contain PAC in a highly dispersed heteroge-
neous distribution. Others are homogeneous and soluble. All of them can be pro-
cessed by conventional techniques such as melt and blow extrusion, fiber spin-
ning, film casting or spin coating. And some of them even provide the necessary
matrix stabilization for turning polyacetylene into a useful material.
Homogeneous types of MATPAC are of special importance. They are based on
highly polar matrix polymers and are soluble in equally polar solvents. They success-
fully prevent the 3-dimensional crosslinking, allow processibility and the buildup of
highly ordered structures, and last-but-not-least stabilize PAC against oxidation.
Yellow, orange, red, violet and blue, and thus the distribution of conjugation
lengths, can be adjusted by using different catalysts at various polymerization
temperatures. Several ligand effects that were already shown to control the molec-
ular weight in ethylene oligo-/polymerizations are again operative in acetylene po-
lymerization in determining the length of the polyacetylene chains. A well-studied
example is PANPAC (Fig. 1.5), a polyacetylene based on polyacrylonitrile, which is
soluble, for example, in dimethylformamide (DMF).
It can be precipitated from and redissolved in DMF or DMSO and processed,
e.g., into fibers. PANPAC with up to and above 70 mol% (!) of solubilized PAC
has been prepared by polymerizing acetylene in polyacrylonitrile/DMF solution