Synthesis of Telechelic Oligomers

The synthesis of telechelic oligomers by oxidative cleavage has been extensively studied by numerous authors and Cheradame [117] reviewed the main reactions leading to telechelic polymers starting from high molecular polymers. As he showed, ozonolysis remains one of the preferred method in addition to Ruthenium tetroxide oxidation to obtain a-co functional oligomers. 

Synthesis of telechelic oligomers usable in the synthesis of multiblock polyesters or polyamides with different segments presenting specific physical properties... 

The synthesis of telechelic oligomers has been brought up in numerous general publications. There are four main ways of synthesis ... 

The scope of this review is to consider all the radical techniques leading to a telechelic or a macromonomer structure. To this aim, it will be necessary to illustrate each method with some examples. We also emphasize that the number of studies in this area is numerous and some will be not considered. Indeed, this paper is not an index of publications on the synthesis of telechelic oligomers and macromonomers but more a comprehensive paper on how to achieve such structures by a radical process. Thus, this paper is divided in two distinct parts synthesis of telechelic oligomers in the first part and synthesis of macromonomers in the second part. In the second part, we will also outline the new design of macromonomers. 

In the review paper of Boutevin [2], the different conventional radical polymerizations, such as telomerization or DEP, were mentioned to lead to a telechelic structure. Since 1990 these radical techniques have shown some progress in the synthesis of telechelic oligomers. We can remark that recent investigations into the understanding of the kinetics of the DEP of... 

For more than 10 years all these LRP techniques have provided numerous studies on the synthesis of telechelic oligomers. We show the possibilities offered by each LRP technique to synthesize telechelic oligomers. 

The telomerization process is based on the use of a transfer agent to control both the molecular weight and the chain-end functionality. The mechanism was developed in previous work [12,13]. For a long time, telomerization remained almost the only technique allowing for the synthesis of telechelic oligomers. 

Since the introduction of LRP, only a few studies have been realized on the synthesis of telechelic oligomers by means of telomerization reaction. It is, however, interesting to give a summary of the studies realized in this area since 1990 because very attractive chain-end functionalities can be easily obtained. 

DEP afforded the synthesis of telechelic oligomers [29]. With the telomerization process, DEP appeared to be the first free-radical polymerization leading to telechelic oligomers. Tobolsky [30] first stated the conditions of DEP, i.e., the half life of the growing species has to be equivalent to that of the initiator. These specific conditions result in an unusual high rate of termination, which allows for the synthesis of oligomers. The telechelic structure will be obtained by combining a termination mode exclusively by recombination with the use of a difunctional initiator. 

Acrylates are of particular interest for the synthesis of telechelic oligomers through the technique of DEP. Actually, acrylates are well known to give only recombination as a termination reaction. Also, for the aim of obtaining... 

The use of 1,2-disubstituted tetraphenylethanes is, however, of great interest because it allows for the synthesis of telechelic oligomers in a one-step reaction for monomers such as MMA which give a high amount of dispropor-... 

Scheme 14 Synthesis of telechelic oligomers by chemical modification of prepolymers previously obtained by ATRP...

We will show a few examples illustrating the synthesis of telechelic oligomers by modification of the terminal thioester group. 

As can be seen, very few examples of telechelic oligomers have been reported in the literature, although NMP is also a good alternative for obtaining these kinds of compounds. Noteworthy previous studies were realized for the synthesis of telechelic oligomers bearing associative groups at both ends. 

Figure 3.23 Carother s equation and synthesis of telechelic oligomers by a nonstoichoimetric polycondensation method.

ADMET polymerization and depolymerization methods have been used in the synthesis of telechelic oligomers. The metathesis depolymerization of 1,4-polybutadiene is accomplished in the presence or absence of a monofunctional diene by using either of the catalysts presented in Figure 13. Telechelic oligomers with terminal alkene, ester, and silyl ether and imide functional groups may be... 

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