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Polymerization, anionic methacrylate molecular weight

Some tailor-made homopolymers can serve as starting points for chemical modifications to yield new species. Poly(hydroxyethyl methacrylate) and poly(glyceryl methacrylate) 16), already mentioned, are obtained upon hydrolysis of the OH-protecting groups that allow the anionic polymerization to proceed. Another example is the acid hydrolysis of poly(t-butyl methacrylate), a reaction which proceeds easily to completion, yielding poly(methacrylic acid) of known degree of polymerization and narrow molecular weight distribution 44 45). [Pg.154]

Table 3. Anionic Polymerization of Ethyl Methacrylate Molecular Weight Control... [Pg.358]

The newest form of living polymerization and potentially the most versatile is living radicai polymerization, more formally known as controlled radical polymerization. First discovered for the polymerization of low-molecular-weight methacrylates, it can be applied to styrenics, acrylates, methacrylates, and a variety of other vinyl monomers. A major advantage over anionic polymerization is the relative insensitivity to functional groups. Like all living polymerizations, it was important to establish rapid initiation with slower overall rate of polymerization and at the same time to inhibit any termination or transfer reactions. Normally, this is very complicated in a radical polymerization, so a radical trap is used in combination with high temperatures. The molecules used have much in common with the inhibitors used to stabilize monomers and prevent premature polymerization. [Pg.137]

AlkyUithium compounds are primarily used as initiators for polymerizations of styrenes and dienes (52). These initiators are too reactive for alkyl methacrylates and vinylpyridines. / -ButyUithium [109-72-8] is used commercially to initiate anionic homopolymerization and copolymerization of butadiene, isoprene, and styrene with linear and branched stmctures. Because of the high degree of association (hexameric), -butyIUthium-initiated polymerizations are often effected at elevated temperatures (>50° C) to increase the rate of initiation relative to propagation and thus to obtain polymers with narrower molecular weight distributions (53). Hydrocarbon solutions of this initiator are quite stable at room temperature for extended periods of time the rate of decomposition per month is 0.06% at 20°C (39). [Pg.239]

The vast majority of commercial apphcations of methacryhc acid and its esters stem from their facile free-radical polymerizabiUty (see Initiators, FREE-RADICAl). Solution, suspension, emulsion, and bulk polymerizations have been used to advantage. Although of much less commercial importance, anionic polymerizations of methacrylates have also been extensively studied. Strictiy anhydrous reaction conditions at low temperatures are required to yield high molecular weight polymers in anionic polymerization. Side reactions of the propagating anion at the ester carbonyl are difficult to avoid and lead to polymer branching and inactivation (38—44). [Pg.247]

Polystyrene standards used were narrow molecular weight distribution sample produced by anionic polymerization and available from Pressure Chemical Co. Also sample NBS7C from the National Bureau of Standards was used. The sample of poly n-butyl methacrylate was obtained from Aldrich Chemical. It was produced by free radici polymerization with an Mw of 320,(XK) and an Mn of 73,500 (Cat. No. 18,153-6). [Pg.150]

Preparation and Reactions of S-b-MM. As mentioned in the introduction, we were interested in block copolymers of styrene and alkali metal methacrylates with overall molecular weights of about 20,000 and methacrylate contents on the order of 10 mol%. The preparation of such copolymers by the usual anionic techniques is not feasible. An alternative is to prepare block copolymers of styrene and methacrylic esters by sequential anionic polymerization, followed by a post-polymerization reaction to produce the desired block copolymers. The obvious first choice of methacrylic esters is methyl methacrylate. It is inexpensive, readily available, and its block copolymers with styrene are well-known. In fact, Brown and White have reported the preparation and hydrolyses of a series of S-b-MM copolymers of varying MM content using p-toluenesulfonic acid (TsOH) (6). The resulting methacrylic acid copolymers were easily converted to their sodium carboxylates by neutralization with sodium hydroxide. [Pg.284]

Initiation of MMA polymerization by complexes such as (192) was shown to proceed via a bimetallic bis(enolate) intermediate, arising from the dimerization of a radical anion.478" 80 Such a mechanism481,482 explains why efficiencies with such initiators (calculated from polymer molecular weights) are always <50%. Using a similar methodology, the bimetallic bisallyl complex (198) was shown to polymerize MMA in a living fashion (Mw/Mn 1.1) and triblock copolymers with methacrylate and acrylate segments have been prepared. [Pg.27]

The precipitated silica (J. Crosfield Sons) was heated in vacuo at 120° for 24h. before use. Two grades of surface areas 186 and 227 m g l (BET,N2), were used during this project. Random copolymers, poly(methyl methacrylates) and polystyrene PS I were prepared by radical polymerization block polymers and the other polystyrenes were made by anionic polymerization with either sodium naphthalene or sodium a methylstyrene tetramer as initiator. The polymer compositions and molecular weights are given in Table I. [Pg.298]

Glusker DL, Lysloff I, Stiles E (1961) Mechanism of anionic polymerization of methyl methacrylate II. Use of molecular weight distributions to establish a mechanism. J Polym Sci 49 315-334... [Pg.60]

Spontaneous polymerization of 4-vinyl pyridine in the presence of polyacids was one of the earliest cases of template polymerization studied. Vinyl pyridine polymerizes without an additional initiator in the presence of both low molecular weight acids and polyacids such as poly(acrylic acid), poly(methacrylic acid), polyCvinyl phosphonic acid), or poly(styrene sulfonic acid). The polyacids, in comparison with low molecular weight acids, support much higher initial rates of polymerization and lead to different kinetic equations. The authors suggested that the reaction was initiated by zwitterions. The chain reaction mechanism includes anion addition to activated double bonds of quaternary salt molecules of 4-vinylpyridine, then propagation in the activated center, and termination of the growing center by protonization. The proposed structure of the product, obtained in the case of poly(acrylic acid), used as a template is ... [Pg.27]

In the present section we describe the living anionic polymerization of meth-acrylonitrile by two initiating systems such as the aluminum porphyrin-Lewis acid system and the aluminum porphyrin-Lewis base system which enables the synthesis of poly(methyl methacrylate-h-methacrylonitrile)s of controlled molecular weights. [Pg.72]

Diphenylmethylcarbanions. The carbanions based on diphenyknethane (pKa = 32) (6) are useful initiators for vinyl and heterocyclic monomers, especially alkyl methacrylates at low temperatures (94,95). Addition of lithium chloride or lithium /W -butoxide has been shown to narrow the molecular weight distribution and improve the stability of active centers for anionic polymerization of both alkyl methacrylates and tert-huXyi acrylate (96,97). Surprisingly, these more stable carbanions can also efficiendy initiate the polymerization of styrene and diene monomers (98). [Pg.240]

One of the first detailed studies on these systems was that of Beaman (26), who showed that methacrylonitrile polymerizes by an anionic chain mechanism when treated with various bases, including Na in liquid ammonia at —75° C. He noted also that low molecular weight polymers are obtained from reaction of acrylonitrile with butylmagnesium bromide. Foster (56) extended the liquid ammonia method to copolymerization studies in which acrylonitrile was combined with styrene, with methyl methacrylate and with vinyl butyl sulfone. Satisfactory data were obtained only with the sulfone, in which case there was some tendency for alternation. [Pg.430]


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Methacrylates, polymerization

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Molecular polymerization

Molecular weight polymerization)

Polymeric methacrylates

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