The strong Lewis acid B(C6F5)3 was found to activate complexes of nickel toward the polymerization of norbornene-type monomers. The active species in this reaction is created by the transfer of C 6F5 from boron to nickel. As a result, a class of neutral, single-component nickel complexes was developed containing two electron-withdrawing aryl ligands that polymerize norbornene and norbornenes with functional pendant groups. Active complexes include Ni(C 6F5)2(PPh2CH2C(O)Ph), (η 6 -toluene)Ni-(C6F5)2, and Ni(2,4,6-tris(trifluoromethyl)phenyl)2(1,2-dimethoxyethane). In the case of (η 6 -toluene)Ni-(C6F5)2, isolation and characterization of low molecular weight norbornene polymers, using ethylene, indicated that each polymer chain contained a C6F5 headgroup. This points to the initiation step as being the insertion of norbornene into the Ni-C6F5 bond. The polymer microstructure as revealed by 1 H and 13 C NMR spectrometry is entirely different from that produced using the cationic nickel catalyst, [(η 3crotyl)Ni(1,4-COD)]PF6. This difference in microstructure led to improved mechanical properties for 80: 20 copolymers of norbornene and 5-triethoxysilylnorbornene.

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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