Telechelic polymers agents

The resulting polymers always have the same functional group X at both chain ends. Therefore, telechelic polymers can be readily synthesized by the two-component iniferter system. An example is the polymerization of several monomers with 4,4J-azobiscyanovaleric acid (16) and dithiodiglycolic acid (17) as the initiator and the chain transfer agent, respectively, to synthesize the polymers having carboxyl groups at both chain ends [69]. 

New Telechelic Polymers and Sequential Copolymers by Polyfunctional Initiator-Transfer Agents (Inifers) End Reactive Polyisobutylenes by Semicontinuous Polymerization... 

Figure 6. Expected change in the equilibrium modulus, Gg, with respect to its ideal value for a perfect network, Gg produced by a 3% change in conversion, AC, functionality, Af the molar ratio [OH]/[NCO], Ar, and cyclization, AC in dependence on conversion. The data refer to a system composed of. trifunctional telechelic polymer and difunctional coupling agent. (Reproduced with permission from Ref. 42. Copyright 1987 CRC Press.)...

Note 1 Reactive end-groups in telechelic polymers come from initiator or termination or chain transfer agents in chain polymerizations, but not from monomer(s) as in polycondensations and polyadditions. 

Termination may also occur by chain transfer with the initiator (e.g., water or alcohol) or a deliberately added chain-transfer agent. Deliberate termination of growth is carried out to produce polymers with specific molecular weights or, more often, telechelic polymers with specific end groups. Hydroxyl and amine end groups are obtained by using water and ammonia as chain-transfer agents. Carboxyl-ended telechelics can be obtained by termination with ketene silyl acetal followed by hydrolysis with base [Kobayashi et al., 1989]. 

In order to synthesize telechelic polymers, the ROMP reaction is carried out in the presence of acyclic olefins that act as chain transfer agents to regulate the molecular weight of the polymers produced. 

J.P. Kennedy and R.A. Smith, New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers). II. Synthesis and characterization of a, a>-di(ferf-chloro)polyisobutylenes,. Polym. Sci., Part A Polym. Chem., 18(5) 1523-1537,1980. 

A series of at least 14 papers [200-208] have been published dealing with the synthesis of telechelic polymers or block copolymers from the radical polymerization of various vinyl monomers with substituted 1,1,2,2-tetraphenyl ethanes. These aromatic compounds, known for over a century [209], are efficient in radical polymerization [201,210], They behave as both initiators and terminating agents [200] that can be involved in living radical polymerization as illustrated in the following reaction ... 

Nonionic amphiphilic telechelic polymers consisting of polyethylene oxide with polyhedral oligosilsesquioxane, POSS, termini were prepared by Mather [3] and used as surfactants and thickening agents. The hydrophobicity of these amphiphilic telechelics, (III), was controlled by varying the molecular weight of the polyethylene oxide component. 

In a subsequent investigation, the author, (3), prepared the nitroxide-mediated polymerization agent, 4,4-dimethyl-2- [ 1 -(2,2,6,6-tetramethylpiperidin-1 -yloxy)-ethyl] -4H-oxazol-5-one, (I), as a method of preparing telechelic polymers. 

Various chain coupling agents are used for telechelic polymers. The functional groups can be grouped into three categories according to their reactivity 186) ... 

Fundamental studies directed toward the elucidation of the mechanism of olefin i.e.f isobutylene, polymerizations yielded a new method for the synthesis of novel linear and tri-arm star telechelic polymers and oligomers [1,2]. The synthesis involves the use of bi- or tri-functional initiator/transfer agents, so called inifers (binifers and trinifers), in conjunction with BCI3 coinitiator and isobutylene, and gives rise to polyisobutylenes carrying exactly two or three terminal -CH2-C(CH3)2Cl groups. These liquid telechelic polyisobutylene chlorides can be readily and quantitatively converted to telechelic polyisobutylene di- or tri-olefins [2,3] which in turn can quantitatively yield by hydroboration/oxidation telechelic polyisobutylene di- and triols [4,5]. 

Similarly, a telechelic polymer bearing carboxylic acid groups at both chain ends was formed by carrying out the lipase-catalyzed polymerization of DDL in the presence of divinyl sebacate [72]. In this case, divinyl sebacate functioned as a coupling agent creating poly(DDL) chains with hydroxyl groups at both termini. 

The direct coupling of monofiinctional polymers prepared by ATRP can also be realized by etherification reaction with low-molar mass dialcohols. Typically, the preparation of aldehyde functional a,co-telechelic polymers by classic etherification is demonstrated on the example hydroquinone as the coupling agent (Scheme 2). 

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