Cyclobutenes copolymerization

Most V-based catalysts of the Ziegler-Natta type cause double-bond opening (addition polymerization) rather than ROMP of cycloalkenes. For example, V(acac)3/Et2AlCl causes only Ziegler-Natta-type addition polymerization of cyclobutene (Natta 1963) and its copolymerization with ethene (Natta 1962). 

The metathesis copolymerization of the cyclobutene derivative, 7,8-bis(trifluoro-methyl)tricyclo[4.2.2.0 ]deca-3,7,9-triene (MO (7 in Ch. 13), with norbomene or cyclopentene (M2) gives copolymers that are readily converted into acetylene copolymers by elimination of l,2-bis(trifluoro)benzene from the Mi units, but the compositional sequence distribution in these copolymers is difficult to establish (Ramakrishnan 1989b). 

Dienes frequently reduce rates and molecular weights when copolymerized with vinyl monomers and this was a feature of the isobutylene/methylene cyclobutene... 

Metallocene/methylaluminoxane (MAO) catalysts can be used to polymerize and copolymerize strained cyclic olefins such as cyclobutene, cyclopentene, norbornene, DMON and other sterically hindered olefins [205-210]. While polymerization of cyclic olefins by Ziegler-Natta catalysts is accompanied by ring opening [10], homogeneous metallocene [211], nickel [212,213], or palladium [214,215], catalysts achieve exclusive double bond opening polymerization. 

Cyclobutene/ cyclopentene/ " methylenecyclopentene/ cyclohexene/ " cycloheptene/ cyclooctene/ bicyclo[2.2.1]hepta-2-ene (norbornene)/ " " and some derivatives of norbornene " are also known to copolymerize with MA to give noncrystalline equimolar copolymers. 

Relatively few data are published concerning the polymerization of cyclobutene, cyclopentene, cyclohexene, or cyclooctene and their substituted derivatives in the presence of cationic initiators [1], Cyclopentene and cyclohexene proved to be unreactive toward AICI3 at low temperatures (—20°C) in ethyl chloride, but they give dimers, trimers, and tetramers as well as higher polymers with BF3 and hydrogen fluoride [9, 10]. On the other hand, copolymerization of cyclohexene with styrene and a-methylstyrene in the presence of AICI3... 

TABLE 2 Copolymerization of Cyclobutene (CB) with 3-Methylcyclobutene (3MeCB) with Different Catalytic Systems... 

Many of the cycloolefms such as cyclobutene, cyciopentene, norbornene, cyclooctene, and their substituted compounds can be successfully polymerized or copolymerized. " Cyclohexene could not be polymerized until recently, because of the high ring stability and the twisted-chair conformation. ... 

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