ALTERNATING COPOLYMERIZATION AS A ROUTE FOR SYNTHESIS OF NOVEL REACTIVE COPOLYMERS

Polymers with pendant reactive double bonds are useful in a variety of important technologies from lithography to structural composites. The preparation of such polymers can often be problematic because of the reactive nature of the pendant double bond. We have found that it is possible to prepare copolymers with pendant reactive unsaturated allyl groups with reasonable polydispersities and molecular weights via the alternating copolymerization of N-allylmaleimide (I) with substituted styrenes or vinyl ethers. In essence, this is the selective copolymerization of two different double bonds in the presence of a third reactive double bond. We attribute the polymerization selectivity that we have observed to the kinetics of alternating copolymerization. Alternating copolymerizations are known to proceed at faster rates than the homopropagation of their comonomers. We propose, therefore, that this high rate of copolymerization leads to the selective reaction of the electron-rich styrenic or vinyl ether double bond and the electron-poor maleimide double bond with the exclusion of the slower chain transfer step to the maleimide allyl double bond. We have observed that these copolymers have utility as microlithographic resists. Their radiation behavior and lithographic performance, especially as x-ray resists, are reported elsewhere.