Struktur‐eigenschafts‐zusammenhänge für poly(butadien‐g‐styren) ‐ modell‐polymere

Abstract

AbstractIn order to ascertain structure‐property‐relationships of poly(butadiene‐g‐styrene) copolymers the preparation of these model copolymers has been carried out by the anionic copolymerization of butadiene and styryl‐terminated polystyrene macromonomers in solution. With this method it is possible to determine exactly the graft length and to vary the graft density or the polystyrene content. Besides, the products are almost free of homopolystyrene and are not cross‐linked. The almost statistically regular distribution of the polystyrene grafts along the backbone chain has been achieved by the application of the initiator system: sodium tert‐butoxide/n‐butyl lithium.The materials have been tested by the determination of selected mechanical characteristic values. They yielded the following relationships: maxima of properties (stress strain, hardness, elasticity) already appear in the range of molar mass of the PS‐grafts from 5 000 to 8 000 g/mole the position and the width of the maxima depend on the PB/PS‐phase ratio with increasing PS‐content, the tensile strength increases up to about 20 MPa at nearly 40 % the hardness of the products is strongly and linearly influenced by the PS‐content the elasticity shows a maximum in the range of 20 to 25 % PS‐content. All in all, the materials exhibit good thermoelastoplastic behaviour in comparison with the SBS‐three or ‐star block copolymers.Electron microscopic examination of the products result in phase separation phenomena.