A chemically amplified photosensitive and thermosetting polymer based on poly [2,6-di(3-methyl-2-butenyl)phenol (15 mol %)-co-2,6-dimethylphenol (85 mol %)] (3c) and a photoacid generator [(5-propylsulfonyloxyimino-5H-thiophen-2-ylidene)-(2methylphenyl)acetoni trile] was developed. Poly [2,6-bis(3-methyl-2-butenyl)phenol]-co2,6-dimethylphenol)] (3) with high molecular weights (number-average molecular weight similar to 24,000) was prepared by the oxidative coupling copolymerization of 2,6-di(3methyl-2-butenyl)phenol with 2,6-dimethylphenol in the presence of copper(1) chloride and pyridine as the catalyst under a stream of oxygen. The structures of 3 were characterized with IR, H-1 NMR, and C-13 NMR spectroscopy. 3 was crosslinked by a thermal treatment at 300degreesC for 1 h under N-2. The 5% weight loss temperatures and glass-transition temperatures of the cured copolymers reached around 420degreesC in nitrogen and 300degreesC, respectively. The average refractive index of the cured copolymer (3c) film was 1.5452, from which the dielectric constant at 1 MHz was estimated to be 2.6. The resist showed a sensitivity of 35 mJ cm(-2) and a contrast of 1.6 when it was exposed to 436-nm light, postexposure-baked at 145degreesC for 5 min, and developed with toluene at 25degreesC. A fine negative image featuring 8-mum line-and-space patterns was obtained on a film exposed to 100 mJ cm(-2) with 436-nm light in the contact-printed mode. 2004 Wiley Periodicals, Inc.