Alkene copolymerization with

Ziegler-Natta polymerization leads to linear unbranched polyethylene, the so-called high density polyethylene (HDPE), which is denser, tougher and more crystalline. By copolymerization with other alkenes it is possible to obtain linear low density polyethylene (LEDPE) with better mechanical properties than LDPE. Blends of LLDPE and LDPE are used to combine the good final mechanical properties of LLDPE and the strength of LDPE in the molten state. 

A variety of reactants—including sulfur dioxide, carhon monoxide, and oxygen, which do not homopolymerize—undergo radical copolymerization with alkenes to form polymeric sul-fones [Bae et al., 1988 Cais and O Donnell, 1976 Dainton and Ivin, 1958 Floijanczyk et al., 1987 Soares, 1997], ketones [Sommazzi and Garhassi, 1997 Starkweather, 1987, and peroxides [Cais and Bovey, 1977 Mukundan and Kishore, 1987 Nukui et al., 1982] ... 

There is a tendency toward alternation in the copolymerization of ethylene with carbon monoxide. Copolymerizations of carbon monoxide with tetrafluoroethylene, vinyl acetate, vinyl chloride, and acrylonitrile have been reported but with few details [Starkweather, 1987]. The reactions of alkenes with oxygen and quinones are not well defined in terms of the stoichiometry of the products. These reactions are better classified as retardation or inhibition reactions because of the very slow copolymerization rates (Sec. 3-7a). Other copolymerizations include the reaction of alkene monomers with sulfur and nitroso compounds [Green et al., 1967 Miyata and Sawada, 1988]. 

The copolymerization of carbonyl monomes with alkenes has been even less studied than that between different carbonhyl monomers. The radiation-initiated copolymerization of styrene with formaldehyde proceeds by a cationic mechanism with a trend toward ideal behavior, r = 52 and r2 = 0 at —78°C [Castille and Stannett, 1966]. Hexafluoroacetone undergoes radiation-initiated copolymerization with ethylene, propene, and other a-olefins [Watanabe et al., 1979]. Anionic copolymerizations of aldehydes with isocyanates have also been reported [Odian and Hiraoka, 1972]. 

Because of its commercial importance, the polymerization of ethylene at high pressure has been extensively studied.204-209 Free-radical polymerization is characteristic of ethylene and vinyl compounds. Simple alkenes, such as 1-butene, however, do not give high-molecular-weight polymers, but they, as well as internal alkenes, can copolymerize with polymerizable monomers. 

Chloromethyl polystyrene can be converted to a free-radical initiator by reaction with 2,2,6,6-tetramethylpipcridinc-/V-oxyl (TEMPO). Radical polymerization of various substituted alkenes on this resin has been used to prepare new types of polystyrene-based supports [123]. Alternatively, cross-linked vinyl polystyrene can be copolymerized with functionalized norbornene derivatives by ruthenium-mediated ringopening metathesis polymerization [124],... 

Higher alkenes are also copolymerized with CO, again in a strictly alternating sense.127... 

The decarboxylation of fluorinated compounds to form fluorinated alkenes has now become very important for the preparation of fluorinated vinyl ethers. These perfluoroalkyl per-fluorovinyl ethers are used as monomers for copolymerization with fluorinated alkenes. in particular tetrafluoroethene. 1,1-difluoroethene, and hexafluoropropene. ... 

Branching can resnlt from the chain-growth process or from branching gronps in the monomers. For example, ethylene can be polymerized by a radical process to a highly branched low-density polyethylene (LDPE) or copolymerized with small amounts of a-alkenes like 1-hexene or 1-octene nsing a metal-mediated catalyst the resnlt is a linear polyethylene punctuated by short-chain branches and known as linear-low-density polyethylene (LLDPE). 

Diynes, such as dipropargyl derivatives, are amenable to cyclopolymerization giving high-molecular-weight polymers (eq. (11), where X = O, S, R2Si, C(C02Et)2, etc). In the presence of an olefin metathesis catalyst, acetylenes copolymerize with each other and with cyclic alkenes. 

The mixture of CpTiCl3, ZnPh2, and MAO has been used to initiate the polymerization of styrene and its copolymerization with 1-hexadecene and with />-/rz -butylstyrene.471 (Ind)TiCl3 combined with ZnPh2 as additive and MAO has been used for the co-polymerization of styrene with 1-alkenes (1-hexene, 1-decene, 1-hexadecene).472 Similarly, CpTiCl3 has been used for the co-polymerization of styrene and p-tert-butylstyrene.473 The syndiotactic polymerization of styrene with Cp TiCl3 and octahydrofluorenyl trimethoxo titanium complexes in the presence of phenylsilane has been investigated.474... 

These nickel-hased compounds with P-O ligands also proved to he capable of ter-polymerizing norbornenes and ethylene with 1-alkenes. As in copolymerizations with ethylene, the level of incorporation of 5- -butylnorbornene in the terpoly-mers was lower than that of norbornene. Additionally, the molecular weights obtained were lower, suggesting that the incorporation of the 1-alkene facilitates chain termination. 

Seebach introduced a novel concept for the immobilization of chiral ligands in PS. The ligand of choice was placed in the core of a styryl-substituted dendrimer 134, which was copolymerized with styrene under suspension polymerization conditions to give the polymeric chiral ligand 135 [74]. The corresponding polymeric (salen) Mn complexes were used to catalyze the enantioselective epoxidation of alkene (Scheme 3.38), with the polymeric complexes being recycled ten times... 

Lewis acids have long been used in both polymerizations and copolymerizations to enhance the reactivities of monomers. The addition of ZnC, alkyl aluminum compounds, or boron halides has been shown to increase both the rate and degree of polymerization of monomers such as acrylonitrile and methyl methacrylate [8]. The use of Lewis acids to enhance electrophilicity of acrylate monomers has also been exploited to enhance alternation in copolymerizations with electron-rich alkenes such as isobutylene [9], Systems that would never produce alternating copolymers can be induced to do so with as little as 0.1 equivalents of an appropriate Lewis acid. This section focusses on efforts to utilize Lewis acids to both alter reactivity and control stereochemistry in copolymerizations. 

Branching of polyethylenes provides the second dimension, after molar mass, with which to control properties. Tables 3.2 and 3.3. Branching of polyethylenes is a complex topic in this review it will be treated starting with the ideal copolymer structures formed with the new metallocene catalysts. Branched polyethylenes (BPE) provide increased toughness though decreased modulus and strength compared with LPE. Branches are obtained by copolymerization with 1-alkenes, such as... 

Ethylene can be copolymerized with alkene compounds or monomers containing polar functional groups, such as vinyl acetate and acrylic acid. Branched ethylene/ alkene copolymers are essentially the same as LDPE, since in commercial practice a certain amount of propylene or hexene is always added to aid in the control of molecular weight. 

The mechanism of RAFT polymerization relies on activation of the monomer double bond to enable efficient fragmentation from the intermediate radical, which in turn provides control over the molecular weight of the resulting polymer. It follows that vinyl monomers, for which the double bond is not activated, are still challenging to polymerize efficiently via RAFT. Although attempts have been made to control the polymerization of 1-alkenes [16] and allyl butyl ethers [17], as yet only copolymerization with active monomers (acrylates and acrylamides) has led to a... 

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