Polymers, anionic functionalization reactions

In order to optimize specific anionic functionalization reactions such as carbonation with carbon dioxide, the effect of chain end structure (stability and steric requirements) has often been investigated. The steric and electronic nature of the anionic chain end and the chain-end aggregation can be modified by reaction with 1,1-diphenylethylene as shown in Eq. (13). When the direct carbonation is effected in benzene at room temperature with the diphe-nylalkyllithium species formed by addition of poly(styryl)lithium to 1,1-diphenylethylene (Eq. 31), the carboxylated polymer can be isolated in 98% yield compared to only a 47% yield for poly(styryl)lithium without end-capping under the same conditions [141] ... 

Alkyl methacrylates, hydrolysis of polymeric ester functionality, 259 Aluminum-hydrogen bond, nucleophilic substitution, 264 Amines alkylation, 28 benzyl-group cleavage, 25 Aminomethylation chloromethylated polymers, 19 Deltfpine reaction, 19 Anionic polymerization advantages, 85... 

Functionalization of these reactive anionic chain ends can be achieved by a variety of methods all based on the general concepts of carbanion chemistry. For example, reaction with C02 or succinnic anhydride leads to the carboxy terminated derivatives [10], while hydroxy-terminated polymers can be easily obtained by reaction with ethylene oxide (Scheme 3) [11]. In select functionalization reactions, such as alkylation with p-vinyl benzyl chloride, the nucleophilicity of the carbanionic species may be necessary and this can be achieved by reaction of the chain end with 1,1-diphenylethene followed by functionalization [12,13]. 

The application of these functionalization reactions to polymers has been catalogued in the anionic polymer review literature (4-6). Unfortunately, many of the reported applications of these functionalization reactions to anionic chain-ended polymers have not been well characterized (7). In order to exploit these functionalization reactions to their potential, well-defined procedures for quantitative chain end functionalization must be available. 

The deliberate introduction of multifunctional branching into anionically prepared polydiene and poly (diene-co-styrene) polymers produces materials with unique morphological and viscoelastic properties (1-3). Work has included synthesis of symmetric star polymers produced by reaction of living polyanionic "arms" with multi-functional chlorosilane (4-9),... 

Telechelic polymers, containing one or more end groups with the capacity to react with other molecules, are useful for synthesizing block and other copolymers [Fontanille, 1989 Hsieh and Quirk, 1996 Nuyken and Pask, 1989 Pantazis et al., 2003 Patil et al., 1998 Quirk et al., 1989, 1996 Rempp et al., 1988]. Living anionic polymers can be terminated with a variety of electrophilic reagents to yield telechelic polymers. For example, reaction with carbon dioxide, ethylene oxide, and allyl bromide yield polymers terminated with carboxyl, hydroxyl, and allyl groups, respectively. Functionalization with hydroxyl or carboxyl groups can also be achieved by reaction with a lactone or anhydride, respectively. Polymers with amine end... 

Most of the methods for synthesizing block copolymers were described previously. Block copolymers are obtained by step copolymerization of polymers with functional end groups capable of reacting with each other (Sec. 2-13c-2). Sequential polymerization methods by living radical, anionic, cationic, and group transfer propagation were described in Secs. 3-15b-4, 5-4a, and 7-12e. The use of telechelic polymers, coupling and transformations reactions were described in Secs. 5-4b, 5-4c, and 5-4d. A few methods not previously described are considered here. 

In a similar way, polymeric azo initiators have been prepared by desactivation of a living anionic polymer with functionalized azo derivatives as azobisisobutyronitrile ( , 12). Concerning this reaction with azobisisobutyronitrile (AIBN), no details on the methanism have been given in the patent litterature. 

Butyllithium initiation of methylmethacrylate has been studied by Korotkov (55) and by Wiles and Bywater (118). Korotkov s scheme involves four reactions 1) attack of butyllithium on the vinyl double bond to produce an active centre, 2) attack of butyllithium at the ester group of the monomer to give inactive products, 3) chain propagation, and 4) chain termination by attack of the polymer anion on the monomer ester function. On the basis of this reaction scheme an expression could be derived for the rate of monomer consumption which is unfortunately too complex for use directly and requires drastic simplification. The final expression derived is therefore only valid for low conversions and slow termination, and if propagation is rapid compared to initiation. The mechanism does not explain the initial rapid uptake of monomer observed, nor the period of anomalous propagation often observed with this initiator. The assumption that kv > kt is hardly likely to be true even after allowance is made for the fact that the concentration of active species is much smaller than that of the added initiator. Butyllithium disappears almost instantaneously but propagation proceeds over periods from tens to hundreds of minutes. The rate constants finally derived therefore cannot be taken seriously (the estimated A is 2 x 105 that of k ) nor can the mechanism be regarded as confirmed. 

In contrast to many other functionalization reactions, termination of living anionic polymers with ethylene oxide, (Eq. (79)) is relatively free of side reactions other than polymerization. For example,... 

The synthetic organic resins consist of cross-linked polymer matrix which is functionalized to provide their ion exchange capacity. The matrix usually must undergo additional reactions to provide the strong acid cation, strong base anion, weak acid cation or weak base anion functionality. 

Scheme 5.15 Synthesis of chain-end-functionalized polymer by reactions of iiving anionic polymers with functionalized...

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