Preparation of block copolymers by polycondensation A critical review

The first part of this chapter is a critical review of the various techniques of polycondensation used in the preparation of block copolymers [2]. It is followed by an analysis of the research trends and future, and the developments of polycondensation reactions leading to the obtaining of thermoplastic elastomers. 

Preparation of block copolymers by polycondensation. A critical review 

Block copolymers can be prepared by ionic and radical polymerizations, including ring-opening polymerization, and by polyaddition and polycondensation. The chemical modification is often associated to other techniques used, e.g., in the preparation of the oligomers (such as end-capping) or the copolymer chains. Chemical modification frequently takes place in one or several steps of a process (see Section 4), 

Block copolymers can be prepared by polycondensation of several a,o -di-functional oligomers or by polycondensation of o ,(j-difunctional oligomers with the precursors of the other blocks. They can be also prepared by the coupling of different difunctional oligomers. Most often, the number of the different oligomers does not exceed 2. 

The direct polycondensation of a,ca-difunctional oligomers leads to well defined block copolymers. The oligomers must be soluble in the reaction mixture or molten and stable when the reaction is carried out in the melt, which is rarely the case of aromatic polymers. Moreover, the direct polycondensation requires that the functionality of the oligomers is exactly 2. 

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