Rubber, styrene-butadiene chain microstructure

Some styrene-butadiene rubber is manufactured by solution processes using alkyllithium catalysts. Production techniques resemble those used for the polymerization of isoprene (Section 18.3.3) and butadiene (Section 18.4.3). Solution styrene-butadiene rubbers have microstructures similar to those of the emulsion copolymers but show narrower molecular weight distribution, less long chain branching and lower non-rubber content. The two types of materials have very similar bulk properties. 

The broad range of control of solution polymer structure and macrostructure of styrene-butadiene rubbers that is only possible using lithium catalysts was discussed in Section 2. We have seen how the microstructure of the butadiene units in the chain and comonomer sequence distribution can be controlled with the addition of polar modifiers and/or variations in pol5onerization process variables. Additionally, the unique control of macrostructure features and the new possibilities offered by reactive functional groups were discussed as part of the molecular engineering capabilities of solution anionic polymerizations. 

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