Ring functionalized polymers from

Interest in anionic polymerizations arises in part from the reactivity of the living carbanionic sites4 7) Access can be provided to polymers with a functional chain end. Such species are difficult to obtain by other methods. Polycondensations yield ro-functional polymers but they provide neither accurate molecular weight control nor low polydispersity. Recently Kennedy51) developed the inifer technique which is based upon selective transfer to fit vinylic polymers obtained cationically with functions at chain end. Also some cationic ring-opening polymerizations52) without spontaneous termination can yield re-functional polymers upon induced deactivation. Anionic polymerization remains however the most versatile and widely used method to synthesize tailor made re-functional macromolecules. 

All the approaches described have been used to prepare functional polymers by cationic ring-opening polymerization. From this point of view, groups of monomers that have been investigated most are cyclic ethers (tetrahydrofuran), cyclic acetals (1,3-dioxolane), cyclic imines (N-f-butylaziridine), and oxazolines, i.e., these monomers for which the living conditions can be approached. 

The melt condensation of acid and hydroxyl functional group normally requires exact stoichiometry, elevated temperature, and a long reaction cycle. Such a route would not be possible to utilize to produce block polymers from lactones and other vinyl monomers. However, a rather facile route leading to polyester formation can be realized by the ring-opening polymerization of lactones as seen from the scheme ... 

A wide variety of difunctional molecules have been converted into polymers by the step-growth process. It is also possible to prepare polymers from a single difunctional molecule if the two functional groups are reactive toward one another. The preeminent example of such a case is the formation of Nylon 6 from caprolactam by ring-opening and subsequent linear polymerization of the resulting amino acid ... 

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