Monomer sequence distribution placements

The examination of monomer sequence distributions by NMR is one of the most extensively used applications in materials science. When two (or more) dissimilar monomers A and B are copolymerized, a polymer is obtained with varying placements of A and B units along the backbone as shown in Fig. 10. It is important to know the relative distribution of monomer sequences, as these have an influence on the polymer s properties, and information about the distributions is valuable for studies of copolymerization mechanism. Initially, NMR was the only technique available to determine monomer sequences. 

Biomacromolecules such as proteins derive their function from their three-dimensional shape and the precise functional group placement on the surface and interior of the structure. Also known as the tertiary structure, this shape is a result of a perfectly controlled monomer sequence, or primary structure. Synthetic polymers containing a perfect monomer sequence are inaccessible using contemporary techniques. However, recent advances in polymerization techniques allow for the fabrication of multi-block polymers with narrow molecular weight distributions " and materials with relatively controlled monomer sequences by step-growth and chain-growth... 

Sequence The difference in reactivity between comonomers affects the composition and also alters the placement of the monomer units along the chain. In the case of living polymerization, sequential monomer addition leads to the formation of block copolymers. However, when a random copolymer is targeted, reactivity differences can lead to nonrandom distribution of monomer units. If the incorporation of a comonomer B is intended to disrupt crystallinity of poly( A), uninteimpted sequences of A can lead to domains of crystallinity. For example, block copolymers of ethylene-propylene are highly aystaUine, while random copolymers are completely amorphous. 

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