Propylene/Cyclic Olefin Copolymers with Cyclopentene, Cyclohexene, Cyclooctene, Tricyclo[6.2.1.0(2,7)]undeca-4-ene, and Tetracyclododecene: The Synthesis and Effect of Cyclic Structure on Thermal Properties

Propylene (P) copolymers with a series of cyclic olefins [cyclopentene (CPE), cyclohexene (CHE), cis-cyclooctene (COE), tricyclo[6.2.1.0(2,7)]undeca-4-ene (TCUE), and tetracyclododecene (TCD)] have been prepared in toluene in the presence of phenoxide-modified half-titanocene catalysts, especially Cp'TiCl2(O-2,6-iPr2C6H3) (Cp' = 1,2,4-Me3C5H2, tBuC5H4), and methylaluminoxane (MAO) cocatalyst. The resultant copolymers are amorphous materials, and their compositions were uniform as confirmed by DSC thermograms [sole glass transition temperatures (Tg)]. The cyclic olefins were incorporated in a 1,2-insertion manner, and the incorporation was affected by the kind of cyclic olefin as well as the nature of catalysts employed. The CHE contents in the copolymers were up to 6.3 mol % (incorporated in an isolated manner), whereas the CPE, COE, TCUE, and TCD contents in the copolymers increased up to ca. 40 mol % (with a mixture of isolated and alternating incorporations) with an increase in the comonomer concentration charged. Linear correlations between Tg values and cyclic olefin contents were demonstrated in all copolymers. The cyclic structure affects the Tg values in the propylene copolymers, except that plots of Tg values vs cyclic olefin contents were close in the P/CPE and P/COE copolymers. In the low cyclic olefin content region (up to 25 mol %), the Tg values in the propylene copolymers were higher than those in the ethylene copolymers.