1,5-Cyclooctadiene)(CH 3 )Pd(Cl)], when reacted in situ with 1 equiv of a monodentate phosphine ligand and 1 equiv of the complex Na + [3,5-(CF 3 ) 2 C 6 H 3 ] 4 B -was found to catalyze the vinyl addition polymerization of norbornene derivatives, including those with pendant oxygen functionalities. For norbornene, a polymerization rate of 1000 tons norbornene/mol Pd‚h was observed at 25°C. For several norbornene derivatives, the molecular weight of the polymer was found to decrease with increasing amounts of added 2-propanol. Mechanistic data confirm a vinyl insertion mechanism for these polymerizations. The polymerization rate was found to decrease dramatically for norbornene derivatives with pendant oxygen functionalities. The effect of coordinating solvents and the uptake of endo vs exo isomers for functionalized norbornenes was tested. Experiments show that (a) the endo isomer reacts more slowly than the exo isomer and (b) both isomers react much more slowly compared to norbornene derivatives lacking coordinating functionalities. Reaction of 5-norbornene carboxylic acid ethyl ester with the [(Et 3 P) 2 Pt(H)] + fragment yields the endo-inserted product exhibiting intramolecular coordination of the ester functionality to the platinum center. The formation of chelates, both upon the coordination of the endo-fuctionalized nobornene and in the endo-inserted product, appears to be responsible, in part, for the observed decrease in polymerization rate for functional norbornene derivates. A further reason for the diminution of activity of both the endo-and the exo-functionalized isomers is simply the coordination of the functionality. Of the two factors, the latter is the dominant one.

A family of high activity catalysts for the vinyl addition polymerization of norbornene-type monomers based on cationic η-allylpalladium complexes coordinated by phosphine ligands has been discovered. The palladium complex [(η3-allyl)Pd(tricyclohexylphosphine)(ether)][B(3,5-(CF3)2C6H3)4] (2) was found to copolymerize 5-butylnorbornene and 5-triethoxysilylnorbornene (95:5 molar ratio) with truly high activity and is capable of producing more than a metric ton of copolymer per mole Pd per hour. Multicomponent catalyst systems based on the addition of salts of weakly coordinating anions (e.g., Na[B(3,5-(CF3)2C6H3)4] or Li[B(C6F5)4]·2.5Et2O) to (η3-allyl)Pd(X)(PR3) (X = chloride, acetate, nitrate, trifluoroacetate, and triflate) in the presence of norbornene-type monomers were developed. NMR tube experiments confirm that Na[B(3,5-(CF3)2C6H3)4] abstracts the Cl ligand from the palladium complex forming the cationic complex in situ. Control experiments confirmed that a high activity polymerization system requires a palladium cation containing an allyl ligand, a neutral, two-electron-donor phosphine ligand, and a weakly coordinating counterion. Those complexes where X contained electron-withdrawing groups such as trifluoroacetate or triflate were found to be the most active catalyst precursors. η3-Allylpalladium catalyst precursors with larger cone angle phosphine ligands yield lower molecular weight polymers. The poly(norbornene) molecular weights can be further tuned by addition of α-olefin chain transfer agents to the reaction mixture. The catalyst systems were also found to polymerize norbornene-type monomers in aqueous media to high conversion at very low catalyst loadings. The effect of molecular weight on thermomechanical properties was explored.

Summary: Homopolymers of a bis‐trifluorocarbinol substituted norbornene (1) (α,α‐bis(trifluoromethyl)bicyclo[2.2.1]hept‐5‐ene‐2‐ethanol or HFANB) and copolymers of 1 with t‐butyl ester of 5‐carboxylic acid (2, t‐BuEsNB) were produced using palladium catalysts and olefinic chain transfer agents such as 1‐hexene and ethylene to control molecular weight. However, these low‐molecular‐weight polymers exhibited relatively low optical transparencies at 193 nm. In fact, the opacity (measured as optical densities in absorbance units per micron) of thin films of these homo‐ and co‐polymers was inversely proportional to their molecular weight. This relationship is consistent with an end group contribution to the film opacity. Spectroscopic analysis of these polymers by 1H NMR and MALDI‐TOF MS confirmed that 1‐hexene and ethylene chain transfer agents generated olefin‐terminated vinyl addition polymers. The olefinic end group contribution to optical density can be eliminated by appropriate chemical modification. Both epoxidation and hydrogenation of the polymer olefinic end groups generated very low optical density materials, independent of molecular weight, that are suitable as 193‐nm photoresist binder resins.End group modification of vinyl and hexenyl‐terminated homopolymers of 1 by epoxidation or hydrogenation.magnified imageEnd group modification of vinyl and hexenyl‐terminated homopolymers of 1 by epoxidation or hydrogenation.

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