Polymers functional telechelic

End-functional polymers, including telechelic and other di-end functional polymers, can be produced by conventional radical polymerization with the aid of functional initiators (Section 7,5.1), chain transfer agents (Section 7.5.2), monomers (Section 7.5.4) or inhibitors (Section 7.5.5). Recent advances in our understanding of radical polymerization offer greater control of these reactions and hence of the polymer functionality. Reviews on the synthesis of end-functional polymers include those by Colombani,188 Tezuka,1 9 Ebdon,190 Boutevin,191 Heitz,180 Nguyen and Marechal,192 Brosse et al.rm and French.194... 

SYNTHETIC METHODS SILICON-CONTAINING POLYMERS, FUNCTIONALIZED POLYOLEFINS, AND TELECHELICS... 

Diol-functionalized telechelic polymers have been desired for the synthesis of polyurethanes however, utilizing alcohol-functionalized a-olefins degrades both 14 and 23. Consequently, in order for alcohols to be useful in metathesis depolymerization, the functionality must be protected and the oxygen atom must not be /3 to the olefin or only cyclic species will be formed. Protection is accomplished using a/-butyldimcthylsiloxy group, and once protected, successful depolymerization to telechelics occurs readily. 

The prepolymers described above are one type of telechelic polymer. A telechelic polymer is one containing one or more functional end groups that have the capacity for selective reaction to form bonds with another molecule. The functionality of a telechelic polymer or prepolymer is equal to the number of such end groups. The macrodiol and macrodiisocyanate telechelic prepolymers have functionalities of 2. Many other telechelic prepolymers were discussed in Sec. 2-12. (The term functional polymer has also been used to describe a polymer with one or more functional end groups.)... 

Condensations of functionalized polymers or telechelics with AIBN or AIBN derivatives are the most frequently described examples of the al (see Sect. 4.2) type synthesis. Depending on the functionality of the reactants and their concentration ratio, a variety of prepolymers with different numbers of azo groups can be synthesised. 

Moreover, in situ polyurethane formation was performed by irradiation of the polymeric pyridinium salt in THF containing toluene diisocyanate and catalyst. It is clear that alkoxy pyridinium terminated polymers are useful materials as precursors for block copolymers and hydroxy functional telechelics. The latter are particularly attractive in photoinduced polycondensation and in applications where hydroxyl groups are needed to be protected. 

CCT of benzyl methacrylate leads to a mixture of poly(benzyl methacrylate) macromonomers from which the dimer macromonomer could be isolated.516 When the benzyl dimer is used as a RAFT chain-transfer agent, PMMA with a- and co-terminal benzyl methacrylate units is obtained. Catalytic hydrogenation of the a,co-benzyl terminal methyl methacrylate polymer results in the evolution of toluene and formation of a,co-dicarboxyl functional telechelic PMMA. 

The synthesis of end-functionalized (telechelic or semitelechelic) polymers has been the subject of numerous studies over the last decades due to both the academic and industrial interest developed for these polymers (1 4). The incorporation of end groups is capable to lead to dramatic changes in the dilute solution (5-7) and bulk properties (8,9) of the parent materials giving rise to practically and potentially numerous applications. 

The development of living cationic polymerization systems for vinyl ethers also enabled the incorporation of functional end groups as well as the control of the polymer architecture. Telechelic polymers have been prepared based on bifunctional initiating systems [59, 50, 60] while... 

Another metaflo-supramolecular system, on the basis of 2,6-bis(l,2,3-triazol-4-yl)pyridine (BTP) as well as Zn and Eu ", respectively, was introduced by Weng and coworkers [95], The approach is quite different from the majority of mechanically responsive metaflo-supramolecular polymers heretofore described the ligands were designed to be part of the polymer backbone instead of being located at the end of the polymer chains. Telechelic pTHF was thus copolymerized with the dUiydroxy-functionalized BTP ligand and hexamethylene diisocyanate to produce a polyurethane that was further cross-linked through the addition of metal ions (Fig. 28a). The metal-rich domains phase-separate from the pTHF soft... 

Three methods were developed to overcome transfer to monomer. These are (1) use of inifers (2) use of proton traps and (3) establishing conditions under which the rate of termination is much faster than the rate of transfer to monomer. The first one, the inifer method, is particularly useful in formation of block copolymers. It allows the preparation of head and end (a and to) functionalized telechelic polymers. Bifunctional initiators and transfer agents (inifers) are used. The following illustrates the concept ... 

FUNCTIONAL, TELECHELIC POLYMERS DERIVED FROM REACTIONS OF NUCLEOPHILIC OLIGOMERS AND ALKEYNL AZLACTONES, PART I TELECHELIC ACRYLAMIDES DERIVED FROM REACTIONS OF ALKEYNL AZLACTONES AND AMINE-TERMINATED OLIGOIERS ... 

Both in Chapter 10 and this chapter, we have described new techniques for the preparation of functional, telechelic oligomers and polymers based on reactions of alkenyl azlactones (Scheme 10). Nucleophilic ring-opening reactions can be utilized for the preparation of fluid acrylamides for potential use in a variety of free radical curable resin systems whereas, Michael addition leads to fluid multiazlactones which may be subsequently cured via nucleophilic addition. Further investigations concerning the chemistry and practical utility of these novel resin systems are ongoing in our laboratories. 

Because of the reversibility of the polymerization and the high reactivity of the oxonium functions, bi- and trifunctional PTHFs are not easy to use. However, addition of a nucleophile to a solution of living polymer yields telechelics that are easier to handle (300). End-capping reagents and the resulting end groups are shown in Table 7. 

Using the rst approach, Sumerhn and coworkers (Gondi et al., 2007) synthesized functional telechelic polymers for which two novel azido-functionalized chain trasfer agents (CTAs), namely, (Xn) and (XIII) (see Fig. 12.18), were prepared and employed to mediate the RAFT polymerization of styrene (St) and Af,Af-dimethylacrylamide (DMA) under a variety of conditions. Poly-... 

While end-functional polymers are clearly important industrial products for materials synthesis, they are also interesting from an academic point of view. Many complex macromolecular architectures can be realized from end-functional polymeric starting materials. Two mono-telechelic polymers can, for example, be joined to form a diblock copolymer, or several such polymers can be joined to form star-like polymers. Mono-telechelic polymers can also be attached to a linear, multifunctional polymer to yield graft copolymers. Depending on the functional end group, such polymers can attach to macroscopic or nanoparticle surfaces or form conjugates with bio-oligomers [5] or biomacromolecules [6]. 

Watson and Wagener [95] reported a tandem ADMET polymerization/ hydrogenation approach to acetoxy-end-functionalized telechelic polyethylene. DCD was polymerized in the presence of 9-decenyl acetate to form the corresponding di-ester-functionalized homo-telechelic polymer. The crude unsaturated polymer was intimately mixed with silica gel and exposed to 120 psi of H2 at 90 °C. The silica gel was added to suppress catalyst homo-dimerization, and the hydrogenated polymer was recovered as the di-ester-functionalized telechelic polyethylene with a molecular weight of 1.5 X 10 g moD fDP = 48) and a PDI of 1.9. 

Employing cfs-l,4-diacetoxy-2-butene as a CTA in the polymerization of COD catalyzed by 2, Hillmyer and Pitet [28] prepared telechelic PBD (Figure 5.7). The base-catalyzed hydrolysis of the acetoxy chain-end groups afforded a hydroxyl-functionalized telechelic polymer (M = 16.5 kDa, MWD = 1.72), which was used as a macro initiator for the ring-opening polymerization of lactide (LA), catalyzed by triethylaluminum. A series of triblock copolymers were synthesized with a polylactide (PLA) content ranging from 24 to 89%, which were shown... 

Scheme 13 Synthesis of diol-functionalized telechelic polymer through radical coupling reaction. Reprinted with permission from Yamago, S. Chem. Rev. 2009, 109, 5051. Copyright 2009 American Chemical Society.

In addition to the initiator-controlled polymer functionalization, transfer reactions may result in functional polymers. In free-radical polymerization, thiols are often employed as chain transfer agents. Chain transfer reactions involving thiols proceed via atom abstraction, as illustrated in Scheme 3. Consequently, these molecules do not offer any scope for introducing functionalities at both ends. However, monofunctional telechelics have been successfully prepared by using thiols. For example, Boutevin and co-workers [39,40] introduced polymerizable vinyl groups to polyvinylchloride accord-... 

The term living polymerization describes any chain growth polymerization that proceeds in the absence of chain termination and chain transfer reactions. This condition of uninterrupted chain growth confers great synthetic utility, enabling the synthesis of sophisticated macromolecules such as block copolymers, star polymers, end-functional (telechelic) polymers, uniform graft copolymers, etc. 

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