화학공학소재연구정보센터
Macromolecules, Vol.36, No.20, 7422-7431, 2003
Stereospecific ring-opening metathesis polymerization of cycloolefins using novel molybdenum and tungsten complexes having biphenolate ligands. Development of crystalline hydrogenated poly(endo-dicyclopentadiene) and poly(norbornene)
Novel molybdenum- and tungsten-based catalysts induced stereospecific ring-opening metathesis polymerization (ROMP) of cycloolefins to produce a new class of crystalline polymers. Various monomeric molybdenum(VI) and tungsten(VI) complexes of the general formula M(=O)(O-Ar)(4) (M = Mo or W; (O-Ar)(4) is two biphenolate or four phenolate ligands) were prepared. These catalysts exhibited moderate ROMP activity in the presence of cocatalyst such as n-BuLi and Et3Al. The molybdenum and tungsten complexes bearing substituted biphenolate ligands such as oxomolybdenum(VI) bis(racemic-5,5',6,6'-tertamethyl-3,3'-di-tert-butyl-1,1'-biphenyl-2,2'-diolate) promoted cis and isospecific ROMP of endodicyclopentadiene (cis > 90% and meso > 95%). The novel ternary and quarternary catalysts such as MoOCl4-biphenolate-n-BuLi (1:2:2) were developed as a new useful methodology to control the stereoselectivity of the ROMP. Hydrogenation of the cis-isotactic poly(endo-dicyclopentadiene)s and poly(norbornene)s provided novel crystalline polymers with high melting points (295 degreesC, DeltaH = 50 J/g; 175 degreesC, DeltaH = 60 J/g, respectively), which can be regarded as a new class of crystalline polymers.