Initiators acrylic ester polymerization

Other Plastics Uses. The plasticizer range alcohols have a number of other uses in plastics hexanol and 2-ethylhexanol are used as part of the catalyst system in the polymerization of acrylates, ethylene, and propylene (55) the peroxydicarbonate of 2-ethylhexanol is utilized as a polymerization initiator for vinyl chloride various trialkyl phosphites find usage as heat and light stabHizers for plastics organotin derivatives are used as heat stabHizers for PVC octanol improves the compatibHity of calcium carbonate filler in various plastics 2-ethylhexanol is used to make expanded polystyrene beads (56) and acrylate esters serve as pressure sensitive adhesives. 

The lanthanocene initiators also polymerize EtMA, PrMA and BuMA in a well-controlled manner, although syndiotacticity decreases as the bulk of alkyl substituent increases. Reactivity also decreases in the order MMA EtMA > PrMA > BuMA. Chain transfer to provide shorter polymer chains is accomplished by addition of ketones and thiols.460 The alkyl complexes (190) and (191) also rapidly polymerize acrylate monomers at 0°C.461,462 Both initiators deliver monodisperse poly(acrylic esters) (Mw/Mn 1.07). An enolate is again believed to be the active propagating species since the model complex (195) was also shown to initiate the polymerization of MA. 

In contrast to the above polymerizations via anionic and/or coordination anionic mechanisms, radical polymerization initiated with metalloporphyrins remains to be studied. The only example of controlled radical polymerization by metalloporphyrins has been reported by Wayland et al. where the living radical polymerization of acrylic esters initiated with cobalt porphyrins was demonstrated. In this section the radical polymerization of MMA initiated with tin porphyrin is discussed. 

Fadner (42) reported preliminary results of electrically initiated polymerization experiments where liquid vinyl monomers are isolated from the electrodes. Liquid ethyl acrylate, for example, absorbed on a filter paper was polymerized in an alternating electric field. The filter paper was sandwiched between two layers of 1.5-mil Mylar film and placed between flat, parallel aluminum electrodes. Conversions of monomer to polymer ranged from 10 to 85% in the range between 20 and 240 sec at up to 25 kcps power. Acrylic acid and its ester polymerized most readily, others, such as styrene and vinyl chloride, resulted only in low yields in the same condition. 

Initiators -for acrylamide [ACRYLAMIDE POLYMERS] (Vol 1) -anionic initiators [INITIATORS - ANIONIC INITIATORS] (Voll4) -cationic initiators [INITIATORS - CATIONIC INITIATORS] (Vol 14) -in emulsion polymerization [LATEX TECHNOLOGY] (Vol 15) -for fluorocarbon elastomers [ELASTOMERS, SYNTHETIC - FLUOROCARBON ELASTOMERS] (Vol 8) -Free-radical initiators [INITIATORS - FREE-RADICAL INITIATORS] (Voll4) -organohthium compounds as [LITHIUM AND LITHIUM COMPOUNDS] (Vol 15) -peroxides as [PEROXIDES AND PEROXIDE COMPOUNDS - INORGANIC PEROXIDES] (Vol 18) -for propylene oxide [PROPYLENE OXIDE] (Vol 20) -for PUR polyols [POLYETHERS - PROPYLENE OXIDE POLYMERS] (Vol 19) -of suspension polymerization [ACRYLIC ESTER POLYMERS - SURVEY] (Vol 1)... 

Enolate Initiators. In principle, ester enolate anions should represent the ideal initiators for anionic polymerization of alkyl methacrylates. Although general procedures have been developed for the preparation of a variety of alkali metal enolate salts, many of these compounds are unstable except at low temperatures (67,102,103). Useful initiating systems for acrylate polymerization have been prepared from complexes of ester enolates with alkali metal alkoxides (104,105). 

Natta, Farina and Donati (123) found that optically active menthyl ethyl ether complexed with butyl lithium initiated asymmetric polymerization of optically inactive sorbic and /9-styryl acrylic esters. This strongly suggests that monomer orientation occurs during coordination with lithium by steric interaction with the asymmetric ligand. Similarly, asymmetric polymers were obtained using optically active 2-methyl-butyl lithium wherein the asymmetric polymer chain directed the monomer orientation. 

Of a large number of possible fluorinated acrylates, the homopolymers and copolymers of fluoroalkyl acrylates and methacrylates are the most suitable for practical applications. They are used in the manufacture of plastic lightguides (optical fibers) resists water-, oil-, and dirt-repellent coatings and other advanced applications [14]. Several rather complex methods to prepare the a-fluoroalkyl monomers (e.g., a-phenyl fluoroacrylates, a-(trifluoromethyl) acrylic and its esters, esters of perfluoromethacrylic acid) exist and are discussed in some detail in [14]. Generally, a-fluoroacrylates polymerize more readily than corresponding nonfluorinated acrylates and methacrylates, mostly by free radical mechanism [15], Copolymerization of fluoroacrylates has been carried out in bulk, solution, or emulsion initiated with peroxides, azobisisobutyronitrile, or y-irradiation [16]. Fluoroalkyl methacrylates and acrylates also polymerize by anionic mechanism, but the polymerization rates are considerably slower than those of radical polymerization [17]. 

As the functionality of the (acrylic ester-diene) copolymers l8,19> is higher than two, the disproportionation mechanism is unimportant and may be neglected. That means that in the diazo-initiated polymerization, termination mostly takes place by recombination. 

Contrary to acrylic esters or acrylonitrile, a vinyl ketone could be polymerized with aluminum (or zinc) alkyl alone in the absence of any added Lewis bases. The mechanism of polymerization of phenyl vinyl ketone(PVK) was studied by using a model initiator, ethylzinc-1,3-diphenyl-l-pentene-l-olate (ZC), which possessed the same structure (see below) as the growing chain end in zinc alkyl-initiated polymerization of PVK (12). 

The free-radical polymerization process with allyl esters resembles that of vinyl and acrylic esters in that there are similar initiation, propagation, and... 

The polymerization of acrylic and vinyl esters generally proceeds quite rapidly, with relatively low levels of initiators, to form products of considerable molecular weight. By contrast, allyl esters polymerize slowly with high levels of... 

Powells et al. pdymerized stereospecifica% deuterated acrylic and methr acrylic esters to h y isotactic polymers tmder several conditions with a number of anionic initiators. They analyzed the polymers by NMR spectroscopy to get the information on the mode of monomer approach to the growing anion. The results of the polymerization initiated with fluorenyllithium suggest that there are two transition states leading to an isotactic placement which differ in the degree of solvation. One is derived from a naked contact ion pair and forms the polymer of threo-meso configuration. The other is apparently formed by the specifically solvated contact ion pair and forms erythro-meso. A very similar study was reported on the anionic polymerization of deuterated ntethyl acrylate. " ... 

Thus, one should expect similar behavior for transition metal enolates where there is significant covalent character to the M-O (or M-G) bond. This section will focus on polymerization of (meth)acrylate esters by group 4 metallocene (or the related group 3 and lanthanocene ") initiators where the mechanism of this process is analogous to the classical GTP process. Of course, the polymerization of (meth)acrylates by other transition metal complexes has been reported frequently in the literature however, in many cases the mechanisms of these processes are less well understood or involve free radical or other forms of initiation. Recent examples of other transition metal-mediated methyl methacrylate (MMA) polymerization processes that may proceed via a GTP or anionic mechanism are given. " "- " ... 

In relation to the mechanism of polymerization, the cobalt octabromo derivative (7b) is also an effective initiator for controlled free-radical polymerization of acrylic esters, where the apparent first-order rate constant of propagation (kapp) at 50 °C is more than 30 times larger than kapp using 7a under identical conditions. This is due to a higher concentration of radicals resulting from greater dissociation of the dormant organocobalt species. 

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