Ring-opening metathesis polymerization of tetracyclododecene using various catalyst systems

Ring-opening metathesis polymerization (ROMP) of a polycyclic olefin monomer (tetracyclododecene, TCD) was carried out using various catalyst systems. The catalysts included titanium-based ternary system (titanium tetrachloride, TiCl₄/triethylaluminum, Et₃Al/triethylamine, Et₃N), tungsten-based ternary system (tungsten hexachloride, WCl₆/triisobutyl aluminum, (i-Bu)₃Al/ethanol), and a ruthenium benzylidene catalyst (Grubbs 1st catalyst). The Grubbs 1st catalyst was most active in ROMP of TCD. The tungsten-based catalyst was found to be more active than the titanium-based catalyst. In contrast to the titanium-based and the Grubbs 1st catalysts, ROMP of TCD with the tungsten-based catalyst was very sensitive to gelation in the course of reaction. The effects of ethanol, WCl₆ concentration, TCD/WCl₆ ratio, and 1-hexane on the polymerization yield and the polymer gel formation were investigated in detail, and optimized ROMP conditions were determined. Chemical structure of synthesized polymer was characterized using one- and two-dimensional 150 MHz ¹³C and 600 MHz ¹H nuclear magnetic resonance spectroscopy, molecular weights were measured using gel-permeation chromatography, and thermal properties were characterized using differential scanning calorimetry. Number-average molecular weights (Mn) of the polymer were in the range of 1.5-4.7 x 10⁴ g/mol, and glass transition temperatures were in the range of 185-220°C.