Synthesis Of Novel Molybdenum Coordination Compound And Its Catalytic Performance In The Polymerization Of DCPD

There are many kinds of catalysts for ring-opening metathesis polymerization（ROMP） of dicyclopentadiene （DCPD）, among them, two component catalyst oftungstenic or molybdenic compounds and alkylaluminium proved to be the mostpopular one. At present, tungten catalysts are popular in the current research andapplication, but, molybdenum catalysts have been rarely reported.Firstly, five kinds of MoCl₅-phenol catalysts with different substituents wereprepared, including MoCl₅-p-Cresol, MoCl₅-Nonylphenol, MoCl₅-264, MoCl₅-2,4,6-Tribromophenol, MoCl₅-dinitrophenols. The activity of different catalyst and theinfluences of different conditions on the polymerization of DCPD were investigated.During the five catalysts, MoCl₅-p-Cresol catalyst has the best activity, themonomer conversion was98.07%and crosslinking degree was90.44%. This may dueto the relationship between the catalyst’s activity and ligand’s electronic effect andstereo-hindrance effect. The phenol ligands with electron-donating groups and a smallstereo-hindrance have a higher activity than electron-withdrawing groups. The resultsshowed that with the increase of temperature and the concentration of n（Mo） andn（Et2AlCl）, the gel time decreased, but the monomer conversion and crosslinkingdegree increased first and then decreased. The structural characterization and propertyanalysis of polydicyclopentadiene （PDCPD） showed that the mechanism of thepolymerization of DCPD is ROMP and its glass transition temperature is121.44℃.In order to enhance the solubility of catalysts and improve its activity, five kindsof novel phosphine ligands containing alkoxy group were synthesized, their structureswere confirmed with IR and¹H-NMR. With the ligands above, five kinds of MoCl₅-phosphine catalysts were prapared, and the solubility, activity and stability of catalystswere investigated.The results showed that the introduction of novel phosphine ligands couldincrease the solubility of catalyst in monomer, the catalysts also have superior stability and activity. The reasons maybe on the one hand, alkoxy group supply electron foractive metal central atom, and stable active intermediates were obtained, so thecatalyst have good stability and activity; On the other hand, long chain alkoxy groupsare lipophilic, so they can increase the solubility of catalyst. Catalyst with ligand of tri-（4-octyloxyphenyl）phosphine have the best activity, this may due to that the longeralkoxy groups could wind around active metal central atom, hinder the formation ofactive intermediates, and cause partial catalyst deactivate.