Grafting butadiene

Problem 31.7 1 Irradiation of poly(-l,3-butadiene), followed by addition of styrene, yields a graft copolymer that is used to make rubber soles for shoes. Draw the structure of a representative segment of this styrene-butadiene graft copolymer. 

Butadiene-grafted low density polyethylene Isoprene-grafted low density polyethylene... 

The concept is similar to the grafting of plants in botany. To form a styrene-butadiene graft polymer, already polymerized butadiene is dissolved in monomeric styrene and an initiator is added. Because polybutadiene readily undergoes chain transfer at the allylic sites, polystyrene chains grow on the polybutadiene backbone. This forms high impact polystyrene, a low cost plastic that is otherwise too brittle without the grafting. 

For polymers containing double bonds as in 1,4-poly-1,3-butadiene, graft polymerization also involves copolymerization between the polymerizing monomer and the double bonds of the polymer in addition to grafting initiated by chain transfer. The relative amounts of the two... 

In secondary steps, radical species formed in BR photooxidation are able to initiate the oxidation of the neighbouring styrenic moieties the photooxidation of the styrenic phase is enhanced by the presence of polybutadiene in ABS, compared with PS homopolymer. Butadiene grafting sites, containing tertiary allylic carbon atoms (A), are preferentially oxidized in tertiary hydroperoxides in the first stages of ABS photooxidation rather than in secondary allylic carbon atoms (B) ... 

Anaerobic adhesives contain reactive monomer(s), accelerators, stabilisers or inhibitors, fillers, colorants, modifiers, tougheners (rubbers, butadiene graft, etc.). The chemistry of anaerobic adhesive is complex but the schematic brief of the reaction may be shown as follows ... 

Vega, J.R. Estenoz, D.A. Oliva, H.M. Meira, G.R. Analysis of a styrene-butadiene graft copolymer with the help of a polymerization model. Int. J. Polym. Anal. Charact. 2001, 6, 81-87. 

---