Radical Copolymerization of 2-Trifluoromethylacrylic Monomers. II. Kinetics, Monomer Reactivities, and Penultimate Effect in Their Copolymerization with Norbornenes and Vinyl Ethers

Abstract

Radical copolymerizations of electron-deficient 2-trifluoromethylacrylic (TFMA) monomers, such as 2-trifluoromethylacrylic acid and t-butyl 2-trifluoromethylacrylate (TBTFMA), with electron-rich norbornene derivatives and vinyl ethers with 2,2′-azobisisobutyronitrile as the initiator were investigated in detail through the analysis of the kinetics in situ with 1H NMR and through the determination of the monomer reactivity ratios. The norbornene derivatives used in this study included bicyclo[2.2.1]hept-2-ene (norbornene) and 5-(2-trifluoromethyl-1,1,1-trifluoro-2-hydroxylpropyl)-2-norbornene. The vinyl ether monomers were ethyl vinyl ether, t-butyl vinyl ether, and 3,4-dihydro-2-H-pyran. Vinylene carbonate was found to copolymerize with TBTFMA. Although none of the monomers underwent radical homopolymerization under normal conditions, they copolymerized readily, producing a copolymer containing 60-70 mol% TFMA. The copolymerization of the TFMA monomer with norbornenes and vinyl ethers deviated from the terminal model and could be described by the penultimate model. The copolymers of TFMA reported in this article were evaluated as chemical amplification resist polymers for the emerging field of 157-nm lithography. © 2004 Wiley Periodicals, Inc.