Copolymerization of ethylene and methyl acrylate

Brookhart and co-workers recently reported tantalizing results that were close to constituting true copolymerizations of ethylene and methyl acrylate. ° ° The catalyst employed was the palladium version of the diimine complexes that were previously reported for ethylene and a-olefin homopolymerizations (complexes IV). °° The close qualification... 

Scheme 6. Illustration of Results from Low-Temperature NMR Mechanistic Studies of the Copolymerization of Ethylene and Methyl Acrylate ...

The functional-group tolerance of late metal catalysts is evident, particularly in the copolymerization of ethylene and methyl acrylate by the a-diimine palladium catalysts. 

I g Catalytic Polymerization of Ol ns in Supercritical Carbon Dioxide Table 8.11 Results of copolymerizations of ethylene and methyl acrylate in compressed carbon dioxide. 

A similar inhibition, but not cessation, of polymerization was observed by Brookhart in his work on the copolymerization of ethylene with methyl acrylate that is catalyzed by cationic bisimine-Pd(II) complexes [9]. Here again, the coordination of the oxygen atom of the ester group of acrylate significantly slows down polymerization and leads to lower molecular weight materials (Eq. (3)). 

To explore the possibilities of olefin polymerization in SCCO2, several monomer and catalyst systems have been investigated. Initially, the proof of principle was established by the polymerization of 1-hexene using the Brookhart catalyst in SCCO2. Subsequently, the polymerization of ethylene was studied in detail. Finally, the copolymerization of ethylene with methyl acrylate was assessed. 

Catalyst precursor 2 as shown in Fig. 8.4 was used for the copolymerization reactions of ethylene and methyl acrylate (0.05 mmol catalyst/L) [9, 41]. The in-... 

The cationic Pd(II) catalysts exhibit effective copolymerizations of ethylene and other a-olefins with polar-functionalized comonomers, with the majority of insertions occurring at the ends of branches. Among the best tolerated monomers are those bearing fluorine or oxygen-containing functionalities, such as esters, ketones, and ethers. The copolymerization of ethylene and acrylates, attractive because the monomers are inexpensive and the copolymers exhibit unique physical properties, has been well-studied mechanistically [27,69], Examples of copolymerizations of ethylene and a-olefins with methyl acrylate are shown in Table 4. In general, the amount of comonomer incorporation varies linearly with its reaction concentration and... 

Table 4 Copolymerizations of ethylene and a-olefins with methyl acrylate (MA) by Pd(II) a-diimine catalysts3...

Mecking S, Johnson LK, Wang L, Brookhart M, Mechanistic Studies of the Palladium-Catalyzed Copolymerization of Ethylene and -Olefins with Methyl Acrylate, J Am Chem Soc, 120, 888-899 (1998)... 

Montei and coworkers [240] reported that Nickel complexes [(X,0)NiR(PPh3)] (X = N or P), designed for the polymerization of ethylene, are effective for home- and copolymerization of butyl acrylate, methyl methacrylate, and styrene. Their role as radical initiators was demonstrated from the calculation of the copolymerization reactivity ratios. It was shown that the efficiency of the radical initiation is improved by the addition of PPhs to the nickel complexes as well as by increasing the temperature. The dual role of nickel complex as radical initiators and catalysts was exploited to succeed in the copolymerization of ethylene with butyl acrylate and methyl methacrylate. 

Mecking, S., Johnson, L.K., Wang, L. and Brookhart, M. (1998) Mechanistic studies of the palladium-catalyzed copolymerization of ethylene and alpha-olefins with methyl acrylate. Journal of the American Chemical Society 120,888-899. 

Cationic Pd complexes of the type 6.18 can catalyze the copolymerization of ethylene and polar comonomers such as methyl acrylates (MAs). Structure 6.35 shows another Pd-based cationic precatalyst. Complexes having the general structure 6.36 have also been found to be effective... 

Polymer Composition. Ethylene—acrylic elastomer terpolymers ate manufactured by the addition copolymerization of ethylene [74-85-1] and methyl acrylate [96-33-3] in the presence of a small amount of an alkenoic acid to provide sites for cross-linking with diamines (4). 

The Lewis acidity and reactivity of these alkyl aluminum cocatalysts and activators with Lewis basic polar monomers such as acrylates make them impractical components in the copolymerization of ethylene with acrylates. To address this shortcoming, Brookhart et al. developed well-defined cationic species such as that shown in Fig. 2, in which the counterion (not illustrated) was the now-ubiquitous fluorinated arylborate family [34] such as tetrakis(pentaflurophenyl)borate. At very low methyl acrylate levels the nickel catalysts gave linear copolymers but with near-zero levels of acrylate incorporation. 

In the present paper we pay special attention to block polymers with polypropylene and polyethylene as the initial anionic block. However, both crystalline and amorphous block polymers of ethylene and propylene, butadiene, and several other olefins and dienes have been made by the AFR technique. The second or free radical block has been made from 4-vinylpyridine, 2-methyl-5-vinylpyridine, and mixtures with other monomers, as well as a number of acrylic monomers. Vinyl chloride, vinylidine chloride, vinyl acetate, and several related monomers have not been successfully copolymerized. 

Goodall (12) disclosed late transition metal catalysts that are highly active and are capable of copolymerizing ethylene with polar comonomers, such as acrylic acid and methyl acrylate. Moreover, Goodall catalysts do not require cocatalysts. An example of a Goodall catalyst is provided in Figure 6.6. 

Ethylene copolymers with acrylates represent a significant segment of the ethylene copolymer market, as many LDPE producers use copolymerization as a strategy to obtain products more resistant to displacement by HOPE and LLDPE. Ethylene copolymers with methyl methacrylate and ethyl, butyl, and methyl acrylates are similar to EVA copolymers in properties (discussed later) but have improved thermal stability during extrusion and increased low-temperature flexibility. 

In this section, the polymerization of ethylene and a functional monomer is discussed. For this purpose copolymerization reactions of methyl acrylate (MA) and ethylene using a palladium-based catalyst have been carried out in compressed carbon dioxide at different monomer concentrations and monomer ratios. The incorporation of methyl acrylate and the molecular weight of the polymers have been compared to literature values of polymerizations conducted in dichloromethane. 

Byun, H.S., et al., Poly(ethylene-co-butyl acrylate). Phase behavior in ethylene compared to the poly(ethylene-co-methyl acrylate)-ethylene system and aspects of copolymerization kinetics at high pressures. Macromolecules, 1996. 29(5) p. 1625-1632. 

Copolymerization of ethylene with non-hydrocarbon monomers such as vinyl acetate, methyl acrylate and ajS-dicarboxylic acids, the latter providing an opportunity for ionic cross-linking via metal cations. 

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