Polycondensation Methods Multifunctional Condensation

2 Polycondensation Methods of Preparing Ladder Polymers (Multifunctional Condensation) 

The first attempts to control a synthetic process using multifunctional monomers were published in 1967/68 by Stille and co-workers [9-12]. They condensed 2,5-disubstituted 1,4-benzoquinones 2 with various tetra-functional aromatic compounds 1 containing amino-, hydroxy- and chloro- functionalities. When carrying out the reaction at high tanperature in polar, aprotic solvents such as HMPT (hexamethyl phosphoric acid triamide) they immediately ob- 

The authors feel, that the classification of the synthetic principles applied here is somewhat arbitrary. Multifunctional polycondensations which are conducted in a two-step manner (generation of single-strand intermediates, followed by cyclization), could be classified with the same justification as stepwise processes. On the other hand some of the stepwise syntheses of ladder structures constitute condensations of multifunctional monomers (e.g. the use of butadiynes as starting compounds, see Sect. 4.1.). 

In order to ensue a clear presentation of the results the authors decided to segregate both synthetic principles All synthetic strategies developed from the multifunctional condensations of Stille and Marvel were assigned to this general type of reaction. At the same time the first multistep sequences (polymer-analogous cyclization of poly(methyl vinyl ketone) and polyacrylonitrile) are used as point of reference for the classification of the other type of synthesis (stepwise procedures). 

Various polyheteroaromatic ladder structures were obtained, for example polymers that consist of phenoxazine- (Z -0-), phenothiazine (Z -S-) or quinoxaline- (Z -NH-) subunits with different patterns of the heteroatoms incorporated [6]. 

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