Functional oligomer group

The common synthetic route to bismaleimides or maleimide functionalized oligomers is the condensation of diamines or amino-terminated oligomers with maleic anhydride. Another possibiUty is the use of an AB-type monomer of the following general formula to build the polymaleimide, where X represents a functional group that can be employed in condensation reactions. 

Poly (ary lene ether sulfone)s and poly(arylene ether ketone) have been employed to prepare block and graft copolymers. Generally, the block copolymers can be prepared by reacting functional-group-terminated oligomers with other functional oligomers and monomers. 

General structure of the (Si—X) terminated siloxane oligomers and a list of important reactive functional end groups (X) are given in Table 2. 

Table 2. General structure of (Si—X) terminated organosiloxane oligomers and important functional end groups...

Condensation polymerization and stepwise addition polymerization are, for example, applied for the preparation of block polyesters. The synthesis concepts are different from those of chain polymerization in that at least one monomer is an oligomer with one or two functional end groups, for example polytetrahy-drofurane with a molecular weight of several hundred and OH-end groups (see Example 3-23). If this oligomer partially replaces butandiol in the condensation polymerization with terephthalic acid (compare examples 4-1 and 4-2), a po-ly(ether ester) is obtained with hard ester segments and soft ether segments and with the properties of a thermoplastic elastomer. 

In certain cases also the chemical conversion of functional end groups E of polymers or oligomers is of importance. 

Fig. 4. Siloxane oligomers used for epoxy modification. From top, polyfdimethyl siloxane), polyfdi-methyl-co-methyltrifluoropropyl siloxane), and poly(dimethyl-co-diphenyl siloxane). Aminoethylpiperazine is the functional end group...

Depending on the composition of the monomer feed and the polymerization procedure, different types of heterogeneities may become important. For example, in the synthesis of tailor-made polymers telechelics or macromonomers are frequently used. These oligomers or polymers usually contain functional groups at the polymer chain end. Depending on the preparation procedure, they can have a different number of functional end groups, i.e. be mono-, bifunctional, etc. In addition, polymers can have different architectures, i.e. they can be branched (star- or comb-like), and they can be cyclic. 

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