Styrene-butadiene rubbers molecular features

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. 

The identification of material heterogeneities based on differences in molecular motion is an important feature of NMR imaging. The importance of slow molecular motion for image contrast is demonstrated in Figure 31 with relaxation time parameter images through a partially aged sheet of carbon-black-filled styrene-co-butadiene rubber (SBR) (147). 

MOLECULAR FEATURES OF RUBBERS DERIVED FROM BUTADIENE AND STYRENE AND THEIR RELATIONSHIP TO Tg AND LOSS... 

Solution polymerised rubbers are usually homopolymers of butadiene or copolymers of styrene and butadiene. They can have a variety of behaviours and properties depending on the molecular structure. However, they are classed as one family because of one common feature of the polymerisation process, i.e. the monomers, catalyst and other ingredients are all dissolved in an organic solvent... 

The objective of this chapter is to provide a survey of the technological developments in solution rubbers prepared by homogeneous anionic polymerization. Emphasis will be on butadiene and styrene monomers, and catalyst systems based on organolithiums and their complexes with Lewis bases plus some unpubhshed work on alkahne earths from the authors laboratory. The rubbers thus obtained offer means for control of molecular structural features of polybutadiene and poly(butadiene-co-styrene) that directly relate to the functional properties of tyre rubbers. 

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