Sequence-Regulated Oligomers and Polymers

SEQUENCE-REGULATED OLIGOMERS AND POLYMERS A. General Methodology and Scope 

Among the structural factors that should be controlled in polymer syntheses (Fig. 1, Section I), perhaps the least exploited is the sequence of constitutional repeat units along a polymer main chain. We have already discussed the syntheses of block copolymers, where two or more homopolymer segments are connected, such as AAAAA-BBBBB- -, which is among the most primitive examples of sequence control in synthetic polymers. 

the reaction starts with the addition of hydrogen iodide to n-butyl vinyl ether, which is considered the first repeat unit. To the resulting 

Obviously, although a new monomer is fed equimolar to the growing end at each step, it is imperative to prevent homopropagation (into a sequence such as A-B-B— instead of the intended A-B-C----)- Monitoring the product distribution along with the multistep additions in fact reveals that the further the synthesis proceeds, the more the amount of such undesired products. Further examination also indicated that sequence selectivity is higher for sequences where the reactivity of monomers progressively decreases [177]. 

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