Alternating ethylene-propylene copolymer (alt-EP) was synthesized by hydrogenation of polyisoprene (HCPI) having high cis-1

4 content (ca. 100%)

suitable molecular weight (Mn = 41×104)

and relatively narrow molecular weight distribution (Mw/Mn= 1.02).The hydrogenation of HCPI was carried out with Ni(naph)2/Al(i-Bu)3 catalyst at 60℃ and hydrogen pressure of 4.0 MPa in cyclohexane for 3 h.NMR and FTIR spectra showed that the characteristic peaks of carbon-carbon double bond disappeared in hydrogenated HCPI

indicating that the hydrogenation degree of the resulting polymer was up to 100%.GPC analysis indicated that the alt-EP maintained relatively narrow molecular weight distribution (Mw/Mn= 1.12)

and degradation or crosslinking reaction did not occur during hydrogenation reaction of HCPI.NMR and FTIR spectra as well as WAXD analysis showed that the alt-EP was well-defined ethylene-propylene copolymer having high alternation

and the present completely alternating ethylene and propylene copolymer was synthesized for the first time.Further

the thermal properties of HCPI and alt-EP were examined by TGA and DSC.The glass transition temperature of alt-EP was -63.3℃

whose value is larger than that of HCPI (-66.7℃).The onset temperature of weight loss of alt-EP was 355℃ and much higher than that of HCPI (266℃)

which suggesting that the thermal stability is enhanced upon hydrogenation.