Copolymerization of ethylene with 5-vinyl-2-norbornene (VNB) using the dicyclopentadienylzirconium dichloride/methylaluminoxane (zirconocene/MAO) catalyst system has been shown to occur with regioselective insertion of the endocyclic double bond of VNB into the copolymer chain, leaving the exocyclic vinyl double bond as a pendant unsaturation. The pendant vinyl group in the copolymer can be readily converted to the hydroxy/epoxy group with complete conversion under mild reaction conditions, giving rise to the corresponding functionalized copolymers. The copolymers (parent and functionalized) have been characterized using IR, NMR, TGA, DSC, and intrinsic viscosity measurements.
The copolymerization of ethylene with 2-allylnorbomane (2-ANB) was studied using Ziegler-Natta and homogeneous metallocene catalysts. The copolymers were characterized by IR, NMR, XRD, GPC, and thermal methods. It was found that the copolymers obtained using the TiCIVTIBAL catalyst were heterogeneous and blocky in nature while those obtained using Cp2ZrCl2/methylaluminoxane (MAO) were homogeneous and random in nature. A comparison between ethylene-2-ANB (norbornyl pendant) and ethylene-4-methyl-l-pentene (isopropyl pendant) copolymers led to the conclusion that both the isopropyl and norbornyl pendant give rise to a similar lowering in the values of AH¡ and Tm.
SUMMARYPolymerization of 2-allylnorbornane using TiCl, catalyst results in a polymer which is 40% insoluble in o-xylene at 130"C, whereas with TiCl, catalyst, a polymer with 88% insolubility in o-xylene at 130 "C is obtained. The o-xylene-insoluble fractions gave a very high melting point T, = 355°C. The main features of these polymerizations are low catalyst activity and, in the case of TiCl, catalyst, competitive isomerization of the monomer. Based on a comparison with the properties of an acyclic analogue, poly(4-methyl-1-pentene), the partly insoluble nature of poly(2-allylnorbornane) and its high melting point can be attributed to the presence of the bicyclic pendant.
IntroductionThe study of the coordination polymerization of higher a-olefins is of theoretical and practical interest since their polymers are expected to have high thermal stability and good mechanical properties. The polymer of Cmethyl-I-pentene (l), which has an isopropyl branch at the f%-position, has a melting point of 235°C and possesses excellent optical transparency '). Poly(vinylcyc1ohexane) which contains a cyclohexyl pendant is known to be a tough polymer with a melting point above 30O0C2). Surprisingly, olefins with more complex branching at the f%-position have received practically no attention. One such olefin, which is a bicyclic analogue of 4-methyl-1-pentene, is 2-allylbicyclo[2.2. Ilheptane (2-allylnorbornane) (2ANB, 2). Monomers 1 and 2 differ mainly in the type of branching at the position f% to the unsaturation. It was therefore of interest to examine the properties of poly(2-allylnorbornane) (PANB) and compare them with the properties of poly(4-methyl-lpentene) (PMP) in order to understand the effect of the bicyclic group. Except for a solitary patent 3, there is no report on the homopolymerization of 2-allylnorbornane in the prior literature.
Copolymers of ethylene with propylene, butene-1 and hexene-1 were prepared using a titanium-magnesium (TMC) or a vanadium-magnesium catalyst (VMC). The copolymers were examined for thermal stability by TGA, melting and crystallization behaviour by DSC and crystallinity by XRD. Fractionated samples of ethylene-hexene-1 copolymers were also similarly characterized. Results indicate that VMC produces copolymers with a higher degree of crystallinity and greater compositional homogeneity than TMC.
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