Polymer Polymeric organolithium compounds

We have previously reported the results of careful investigations of the solution carbonation (8) and oxidation (9) of polymeric organolithium compounds. These studies have been extended to the investigation of solid-state carbonation reactions and these results are reported herein. In addition, a new method has been developed for the synthesis of telechelic polymers with primary amine end-group... 

Polymeric organolithium compounds exhibit limited stability in ether solvents similar to alkyllithium compounds. Living carbanionic polymers react with ether solvents such as THF in a pseudo-tirst-order decay process and the rate decreases in the order Li > Na > K. For example, a 10 M solution of poly(styryl)lithium in THF at 25 °C exhibited a rate of decay of a few percent per minute, but poly(styryl)cesium was found to be exceptionally stable [96], Metalation and decomposition reactions can also occur in the presence of amines such as TMEDA. 

Functionalizations via Silyl Hydride Functionalization and Hydrosilation A new general functionalization method based on the combination of living anionic polymerization and hydrosilation chemistry has been developed as illustrated in Scheme 7.26 [281]. First, a living polymeric organolithium compound is quantitatively terminated with chlorodimethylsilane to prepare the corresponding co-silyl hydride-functionalized polymer. The resulting co-silyl hydride-functionalized polymer can then react with a variety of readily available substituted alkenes to obtain the desired chain-end functionalized polymers via efficient regioselective transition-metal-catalyzed hydrosilation reactions [282-284]. 

The reaction of polymeric organolithium compounds with ethylene oxide (EO) is a model specific functionalization reaction. For example, the functionalization of PSLi with 4 equivalents of EO in benzene at 25 ° C proceeds quantitatively with no oligomerization to produce the corresponding co-hydroxyl-ftmctionalized polymer in the absence of polar additives (eqn [4]) ... 

The functionalization of polymeric organolithium compounds with 3,4-epoxy-1-butene (EPB) provides the potential to prepare a polymer molecule with dual functionality as well as a potential precursor to a diene-functionalized macromonomer. It has been shown that the reaction of EPB with methyllithium results in three modes of addition to the... 

In principle, another general method for the preparation of hydroxyl-functionalized polymers is through the reaction of polymeric organolithium compounds with carbonyl compounds. The reaction of polymeric organolithium compounds with the simplest carbonyl compound, formaldehyde, has been reported. ... 

The carbonation of polymeric carbanions using carbon dioxide is one of the simplest, most useful, and widely used functionalization reactions. However, there are special problems associated with the simple carbonation of polymeric organolithium compounds. Eor example, when carbonations with high-purity, gaseous carbon dioxide are carried out in benzene solution at room temperature using standard high vacuum techniques, the carboxylated polymer is obtained in only 27-66% yield for PSLi, PILi, and poly(styrene-b-isopre-nyl)lithium. The functionalized polymer is contaminated with dimeric ketone (23-27%) and trimeric alcohol (7-50%)... 

In conclusion, the secondary amine functionalization of polymeric organolithium compounds with the readily available imine, N-benzylidenemethylamine, has been shown to be efficient for both PSLi and PBDLi.No evidence for dimer formation or unfunctionalized polymer was observed. 

Thus, it is possible to form the very reactive, aldehyde-functionalized polymers by functionalization of polymeric organolithium compounds with 4-morpholinecarboxaldehyde. The key to the success of this procedure is due to the formation of a stable, tetrahedral intermediate that does not decompose to form the aldehyde group until work-up with alcohol. Work-up with acidic methanol is the preferred procedure to prevent dimer formation from base-catalyzed aldol condensation, primarily for functionalizations of poly(dienyl)lithiums. 

The reaction of polymeric organolithium compounds with thiir-anes is reported to be a viable route for the preparation of thiol-functionalized polymers. However, until recently the mechanism of this reaction had not been elucidated, that is, whether this proceeds via a sulfur extmsion reaction (path (a) in Scheme 11) or via a ring-opening reaction (path (b) in Scheme 11). For simple alkyllithium compounds, the sulfur extmsion pathway has been shown to be operative. 

In conclusion, the addition reactions of simple and polymeric organolithium compounds with substituted 1,1-diarylethylenes provide a general method for the synthesis of a and co end-functionalized and labeled polymers. With this method in conjunction with appropriate protecting groups and reaction conditions, a wide variety of well-characterized, quantitatively functionalized and labeled polymers and copolymers can now be prepared with diverse molecular structures. Polymers can be prepared with functional groups either at the initiating chain end or at the terminating chain end. ... 

Many interesting and important synthetic applications of 1,1-diphenylethylene and its derivatives in polymer chemistry are based on the addition reactions of polymeric organolithium compounds with 1,1-diphenylethylenes. Therefore, it is important to understand the scope and limitations of this chemistry. In contrast to the factors discussed with respect to the ability of 1,1-dipheny-lalkylcarbanions to initiate polymerization of styrenes and dienes, the additions of poly(styryl)lithium and poly(dienyl)lithium to 1,1-diphenylethylene should be very favorable reactions since it can be estimated that the corresponding 1,1-diphenylalkyllithium is approximately 64.5kJ/mol more stable than allylic and benzylic carbanions as discussed in Sect. 2.2 (see Table 2). Furthermore, the exothermicity of this addition reaction is also enhanced by the conversion of a tt-bond to a more stable a-bond [51]. However, the rate of an addition reaction cannot be deduced from thermodynamic (equilibrium) data an accessible kinetic pathway must also exist [3]. In the following sections, the importance of these kinetic considerations will be apparent. 

Another dramatic example of the usefulness of DPE end-capping of polymeric organolithium compounds to promote efficient functionalization reactions is the sulfonation reaction using sultones [142]. A careful examination of the functionalization of poly(styryl)lithium with 1,3-propane sultone showed that the corresponding sulfonated polymer (see Eq. 32) was obtained in maximum yields of only 30% and 53% in benzene or tetrahydrofuran, respectively [142] ... 

The reaction of polymeric organolithium compounds with substituted 1,1-di-phenylethylene derivatives (16) has been shown to be an excellent methodology for anionic synthesis of chain-end functionalized polymers (18) (Eq. 35)... 

Polymeric organolithium compounds react simply and quantitatively with 1,1-diphenylethylenes [3, 109]. These reactions have provided a new methodology for the synthesis of star-branched polymers, internally-functionalized polymer chains and stars, as well as heteroarm, star-branched polymers via living linking reactions as shown in Scheme 33 [3, 202, 203, 207]. 

The alkyllithium-initiated, anionic polymerization of vinyl and diene monomers can often be performed without the incursion of spontaneous termination or chain transfer reactions (1). The non-terminating nature of these reactions has provided methods for the synthesis of polymers with predictable molecular weights and narrow molecular weight distributions (2). In addition, these polymerizations generate polymer chains with stable, carbanionic chain ends which, in principle, can be converted into a diverse array of functional end groups using the rich and varied chemistry of organolithium compounds (3). 

In the 1960s, anionic polymerized solutron SBR (SSBR) began to challenge emulsion SBR in the automotive tire market. Organolithium compounds allow control of the butadiene microstructure, not possible with ESBR. Because this type of chain polymerization takes place without a termination step, an easy synthesis of block polymers is available, whereby glassy (polystyrene) and rubbery (polybutadicnc) segments can be combined in the same molecule. These thermoplastic elastomers (TPE) have found use ill nontire applications. 

---