Open-loop Shift Of The Polymerization Of Dicyclopentadiene

Ring-opening metathesis polymerization (ROMP) of cycloolefins has emerged as a powerful tool for macromolecular engineering, among which the ROMP of dicyclopentadiene (DCPD) gains widespread interest because of the availability of DCPD and excellent mechanical properties of polydicyclopentadiene (PDCPD). The situation and development of olefin metathesis, the catalysts used in the ROMP of DCPD and the modification of PDCPD were introduced. The background, meaning and way of this paper were pointed out.Using WCl₆-Et₂AlCl as catalyst system, PDCPD with high performance was synthesized. There are mainly the following aspects in this paper.(1) Many useful alkoxy ligands (-OR) and phenol ligands (-OAr) were introduced into WCl₆ to improve the solvency of WCl₆ in DCPD and increase the catalytic activity of catalyst system WCl₆-Et₂AlCl. P-nonyl phenol was found to be the best ligand. Influence of technological conditions on the catalytic activity of catalyst system was investigated and the optimum conditions are as follows: molar ratio of p-nonyl phenol to WCU, 1.3:1; the concentration of p-nonyl phenol in toluene is the same to the concentration of WCl₆ in toluene; the adding velocity of phenol solution, 1/3×10^-3mol/min; reaction temperature, 35-40℃; reaction time, 6-8h.(2) Using modified WCl₆-Et₂AlCl as catalyst system, PDCPD was synthesized through ROMP simulating reaction injection molding (RIM). The influences of polymerization conditions such as the dosage of cyanobenzene, catalyst, co-catalyst and polymerization temperature on the polymerization (gelation time and monomer conversion) and the swelling value of PDCPD were investigated. The optimum conditions are as follows: molar ratio of cyanobenzene to WCl₆, 3:1; polymerization temperature, 70℃ ; molar ratio of DCPD to WCl₆, 1500:1; molar ratio of Et₂AlCl to WCl₆, 11:1. The influences of post-curing on the structure and property of PDCPD were investigated. The excellent tough structure of PDCPD will be damaged by post-curing which is achieved on the mechanics of cation addition.