Telechelic polymer, defined

Telechelic polymers are defined as macromolecules with reactive sites on the polymer chain, usually as endgroups on linear polymers [106]. This macro-molecular architecture has successfully produced a wide variety of block copolymers using macroinititated polymerizations. Living anionic polymeriza-... 

In the area of novel materials CMU protected (co)polymers prepared by ATRP except with CCI4 initiator and telechelic polymers prepared by CRP with MW > 20,000 (49) copolymers with a tme gradient segment (30) polar ABA block copolymers, (30) and well defined graft copolymers and segmented copolymers with one or more CRP blocks where the macroinitiator had been prepared by another polymerization process. (36) In addition, the use of tethered initiators allowed synthesis of hybrid core/shell copolymers. Pending applications disclose other novel polymeric materials. 

In addition, there has been an increasing interest in new synthetic methods for the preparation of well-defined polymers with controlled chain-end functional groups [23], such as telechelic polymers, which are characterized by the presence of reactive functional groups placed at both chain ends. These materials can then be used as precursors in the synthesis of block copolymers, as modifiers of the thermal and mechanical properties of condensation polymers, as precursors in the preparation of polymer networks, and as compatibilizers in polymer blends [24]. 

A telechelic polymer is defined as a relatively low-molar-mass spedes (M < 20,000), with functional end groups that can be used for further reaction to synthesize block copolymers or for network formation. Cationic polymerization methods can be used to prepare these fimctionalized polymers using the initiator-transfer, or Inifer, technique perfected by Kennedy. If the initiating catalyst-cocatalyst system is prepared from a Lewis acid and an alkyl or aryl halide, i.e.. 

The polymerisation processes described in the previous section are the classical processes used for producing the bulk commercial polymers. Newer processes have been and are being developed with a variety of aims in mind. These involve the production of novel polymer topologies (see box) precise control over chain length and over monomer sequences in copolymers control of isomerism (see section 4.1) production of polymers with special reactive end groups, the so-called telechelic polymers, production of specially designed thermally stable polymers and liquid-crystal polymers with a variety of different structures and properties. Other developments include the production of polymers with very precisely defined molar masses, and of networks with precisely defined chain lengths... 

RAFT-CTAs can be prepared in a similar way and thus combined with ROMP for the synthesis of well-defined block copolymers. ABA-type triblock polymers of 1,5-cyclooctadiene (by ROMP) and St or tBA (by RAFT) were synthesized by Mahanthappa et In the first step of the process, the synthesis of telechelic PBs possessing trithiocarbonate-functionalized termini was performed using the specially designed difanctional CTA containing double bond in the middle. The RAFT polymerizations of conventional monomers mediated by the telechelic polymers gave rise to PSt-b-PB-l7-PSt and PtBA-l -PB-l7-PtBA (Scheme 68). 

Synthesis of block copolymers with well-defined structure has received considerable attention, as their properties are potentially of great interest (see Section 4.1). Until recently, the possibilities were limited to the use of either sequential addition of monomers in living anionic polymerisation systems, or coupling of polymers possessing reactive ends, e.g. telechelic polymers. Advances in radical controlled polymerisation have opened new perspectives. 

Telechelic ionomers are a special class of ionic polymers in which the charged groups are situated exclusively at the chain ends (see Telechelic Polymers (85,86)) Accordingly, their solid-state structure is characterized by self-assembly of the chain ends into ion multiplets or ionic clusters. Because of this defined... 

The two previous methods to introduce functional end groups rely on secondary metathesis reactions and thermodynamic equilibrium to be reached. Polydis-persity indices of PDl = 2 will be obtained out of mechanistic necessity. This can be a major drawback when it comes to highly defined homo-telechelic polymers. A second drawback is the typically required long reaction times to drive the reactions to thermodynamic equilibrium. 

Flory [289] defined chain transfer as the process in which the active center is transferred from one polymer molecule to another molecule, leaving the former inactive and endowing the latter with the ability to add monomers successively. However, the most efficient chain transfer agents contain active halogen, which adds to the growing polymer chain, and hence are not suitable in the preparation of telechelic polymers. 

Xia Y, Verduzco R, Grubbs RH, Komfield JA (2008) Well-defined hquid crystal gels from telechelic polymers. J Am Chem Soc 130 1735-1740... 

Telechelic (or a, co-difunctional) oligomers exhibit functional groups at both ends of the oligomeric backbone. These compounds are quite useful precursors for well defined architectured polymers (e.g. polycondensates, polyadducts and other fluoropolymers previously reviewed [400, 401]). As mentioned above, a... 

Synthesis of Well Defined Copolymer Structures Starting from Ozonized Polymers Block Copolymers, Graft Copolymers, Telechelic Oligomers... 

Anionic polymerization has been the usual route for this type of special synthesis. Cationic [9], catalytic [10], and group transfer [11] polymerizations have been developed to produce well-defined blocks from different classes of monomers. Perhaps the richest and most technologically useful future route to the production of these materials is via so-called telechelic [12] or functionalized polymers. Generically, this refers to block polymers in... 

The versatility associated with nitroxide-mediated polymerizations, in terms of both monomer choice and initiator structure, also permits a wide variety of other complex macromolecular structures to be prepared. Sherrington201 and Fukuda202 have examined the preparation of branched and cross-linked structures by nitroxide-mediated processes, significantly the living nature of the polymerization permits subtlety different structures to be obtained when compared to traditional free radical processes. In addition, a versatile approach to cyclic polymers has been developed by Hemery203 that relies on the synthesis of nonsymmetrical telechelic macromolecules followed by cyclization of the mutually reactive chain ends. In a similar approach, Chaumont has prepared well-defined polymer networks by the cross-linking of telechelic macromolecules prepared by nitroxide-mediated processes with bifunctional small molecules.204... 

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