Synthesis and polymerization of disubstituted cyclooctenes

Abstract

It is well known that the mer sequence of copolymers always exhibits significant effect on their physical properties. However, it is hardly possible to make alternating copolymers with any conventional methods. Thus, many research groups have explored various methods in attempts to synthesize the sequence-controlled copolymers ; ring-opening polymerization, Ziegler-Natta copolymerization, polymer modification and metathesis polymerization. In this study, we concentrated our attention on the syntheses of butadiene based sequence-controlled copolymers, structure analysis of the resulting polymers and thermal property investigation. For the synthesis of these polymers, new 4,6-disubstituted cyclooctenes, 4-methyl-6-phenylcyclooctene and 4,6-diphenylcyclooctene were prepared and polymerized with various metathesis catalyst systems. Theses cyclooctene derivatives exhibited quite different polymerization behavior depending upon the catalyst systems employed. The catalyst system of $W(OAr)_2Cl_4/Et_4Pb$ was most effective. The polymers of 4-methyl-6-phenylcyclooctene are rubbery and show a glass transition at -3.6℃. They are soluble in THF, tolune and methylene chloride. The analysis of the IR, $^1H$-NMR and $^{13}C$-NMR spectra were the structure of 1:1:1 alternating copolymer of butadiene, propylene and styrene. The detail structure of the polymers was further confirmed by the H-C COSY spectrum. The polymers were hydrogenated with Pd/C catalyst. Disappearance of vinylic chracteristic peaks in spectra of the hydrogenated polymers supports that they have the structure of a 2:1:1 alternating copolymer of ethylene, propylene and styrene. The polymers of 4,6-diphenylcyclootene are glassy and soluble in THF, toulene and methylene chloride. The glass transition measured by DSC is 39.2℃. The structure of the polymers was confirmed to be 2:1 alternating copolymer of styrene and butadiene.