Studies On Olefin Polymerization Catalyzed By Mono-cyclopentadienyl-titanium Complex/AlⁱBu₃/Ph₃CB(C₆F₅)₄ Catalytic Systems

Recently, one of the most attractive subjects in the field of polyolefins is the introduction of polar functional groups in polyolefins. This is primarily because polar functionality in polyolefins substantially improves the polymer properties such as permeability, dye ability, and compatibility with other materials. However, the remarkable drawback of group 4 metallocene catalysts is their limited ability to polymerize polar monomers. Thus, much work has recently been focused on the chemical modification of polymers containing reactive site, like vinyl or vinylidene group, etc. Copolymerization ethylene with non-conjugated dienes, such as 4-vinyl-1-cyclohexene, 5-vinyl-2-norbornene, and dicyclopentadiene have been reported to produce copolymers with unsaturated carbon-carbon double bond that can be functionalized via various standard chemical reactions. 5-Ethylidene-2-norbornene (ENB) is a relatively cheap norbornene derivative with an additional carbon-carbon double bond (ethylidene) that does not interfere in the E/ENB polymerization reaction. In this paper, we wish to report the results of the ENB homopolymerization and the E/ENB copolymerization catalyzed by the constrained geometry catalyst 2-tetramethylcyclopentadienyl-4,6-di-tert- butylphenoxytitanium dichloride/AliBu₃/Ph₃CB(C₆F-5)₄ catalyst system, as well as the epoxidation of resulting poly(E-co-ENB). On the other hand, we also report the results of the E/ENB copolymerization catalyzed by the nonbridged half-titanocenes of the type 1-3 as catalysts in the presence of Al i Bu₃/Ph₃CB(C₆F₅)₄, as well as the epoxidation of resulting poly(E-co-ENB). Copolymers of ethylene withα-olefins are important polymer materials in industry because of their excellent performance. Therefore, there has been a continuing interest in the investigation on ethylene/α-olefin copolymerizations. Among these catalysts, the constrained geometry metallocene and nonbridged half-titanocenes of the type catalysts exhibit high catalytic activities and produce ethylene/α-olefin copolymers with uniform compositions and narrow molecular weight distributions.5-Ethylidene-2-norbornene (ENB) polymerization and copolymerization with ethylene (E) catalyzed by constrained geometry catalyst 2-tetramethylcyclopentadienyl-4,6-di-tert-butylphenoxytitanium dichloride were studied in the presence of Al i Bu 3 and Ph₃ CB(C₆ F₅ ) 4. The catalyst system shows good activity on the homopolymerization of ENB, and higher activity on the copolymerization of E/ENB under atmospheric pressure of ethylene. 1H NMR analysis of polymer indicates that ENB was inserted into polymer backbone through the endocyclic double bond regiosectively, leaving the ethylidene double bond unreacted. The effects of the polymerization temperature and initial ENB concentration on the catalytic activity, content of ENB in the copolymer, molecular weight of copolymer, and glass transition temperature of copolymer were examined. The ethylidene group contained in the copolymer was converted to the epoxy group quantitatively with m-chloroperbenzoic acid, producing functionalized poly(E-co-ENB)s. The copolymers (parent and functionalized) have been characterized using IR, NMR, DSC, and GPC techniques. Copolymerization of ethylene and 5-ethylidene-2-norbornene (ENB) using nonbridged (cyclopentadienyl)(aryloxy)titanium(IV) complexes of the type, Cp`TiCl<sub>2</sub>(OAr) [OAr = 2,4,6-tBu<sub>3</sub>C<sub>6</sub>H<sub>2</sub>O and Cp`= Me₅C₅ (1), Me4PhC5 (2), and 1,2-Ph₂-4-MeC₅H₂ (3)], as catalysts was studied in the presence of Al i Bu₃/Ph₃CB(C₆F₅)₄. These catalysts show good activity and produce copolymers with higher ENB incorporation under atmospheric pressure of ethylene. Among these three catalyst systems, the 1/Al(iBu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits highest catalytic activity under same conditions. 1H NMR analysis of polymer indicates that ENB was inserted into polymer backbone through the endocyclic double bond regiosectively, leaving the ethylidene double bond unreacted. The effects of the polymerization temperature and initial ENB concentration on the catalytic activity, content of ENB in the copolymer, intrinsic viscosity of copolymer, and glass transition temperature of copolymer were examined. The differences of the micromechanism between ENB homopolymers and copolymers with similar ENB content produced by the catalysts 1 and 2-tetramethylcyclopentadienyl-4,6-di-tert-butylphenoxytitanium dichloride under similar conditions were analyzed using NMR. On the other hand, the ethylidene in copolymer resultant by 1/Al i Bu₃/Ph₃CB(C₆F₅)₄ catalyst system was converted to the epoxy group quantitatively with m-chloroperbenzoic acid, producing functionalized polymer. The copolymers (parent and functionalized) have been characterized using NMR and IR techniques.Copolymerization of ethylene with 1-octene and 1-octadecene using constrained geometry catalysts 2-(3,4-diphenylcyclopentadienyl)-4,6-di-tert-butylphenoxytitanium dichloride (1), 2-(3,4-diphenylcyclopentadienyl)-6-tert-butylphenoxytitanium dichloride (2), 2-(3,4-diphenylcyclopentadienyl)-6-methylphenoxytitanium dichloride (3), and 2-(3,4-diphenylcyclopentadienyl)-6-phenylphenoxytitanium dichloride (4) was studied in the presence of AliBu3 and [Ph3C][B(C6F5)4]. The differences in the substituents on the phenolate group of the ligand in the 1-4 with the polymerization behaviour in the copolymerization of ethylene with 1-octene and 1-octadecene were related. Among these four catalyst systems, the 1/Al(iBu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits highest catalytic activity and produced highest molecular weight copolymers under same conditions. The effects of the catalyst structure, comonomer, and reaction parameters such as the Al/Ti molar ratio, polymerization temperature, and comonomer feed concentration on the catalytic activity, comonomer incorporation, and molecular weight of the copolymers were also examined. The ratio of rO/rE and rOD/rE are 0.04 and 0.006, respectively, which can be used to compare the relative comonomer incorporation ability under same conditions (1-octene > 1-octadecene). The reactivity ratio product (rE·rO and rE·rOD are 1.094 and 1.067, respectively) values are close to 1, which demonstrates that the ethylene/1-octene and ethylene/1-octadecene copolymerization proceeds in a random manner.Copolymerization of ethylene with 1-hexene, 1-octene, and 1-octadecene using nonbridged (cyclopentadienyl)(aryloxy)titanium(IV) complexes of the type, Cp`TiCl2(OAr) [OAr = 2,4,6-tBu<sub>3</sub>C<sub>6</sub>H<sub>2</sub>O and Cp`= Me₅C₅ (1), Me₄PhC₅ (2), and 1,2-Ph2-4-MeC5H2 (3)], as catalysts was studied in the presence of Al i Bu₃/Ph₃CB(C₆F₅)₄. The differences in the substituents on the cyclopentadienyl group of the ligand in the 1-3 with the polymerization behaviour in the copolymerization of ethylene with 1-hexene, 1-octene, and 1-octadecene were related. Among these three catalyst systems, the 1/Al(iBu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits highest catalytic activity and produced highest molecular weight copolymers under same conditions. The effects of the catalyst structure, comonomer, and reaction parameters such as the Al/Ti molar ratio, ethylene pressure, and comonomer feed concentration on the catalytic activity, comonomer incorporation, and molecular weight of the copolymers were also examined. The ratio of rH/rE, rO/rE and rOD/rE are 0.02,0.01 and 0.001, respectively, which can be used to compare the relative comonomer incorporation ability under same conditions (1-hexene > 1-octene > 1-octadecene). The reactivity ratio product (rE·rH, rE·rO and rE·rOD are 0.55, 0.58 and 0.60, respectively) values are small, which demonstrates that the ethylene/1-hexene, ethylene/1-octene and ethylene/1-octadecene copolymerization does not proceed in a random manner.