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

Abstract

In order to ascertain structure-property-relationships of poly(butadiene-g-styrene) copolymers the preparation of these model copolymers has been camed 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-butoxideln-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 OOO to 8 OOO glmole 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 SBSthree or -star block copolymers. Electron microscopic examination of the products result in phase separation phenomena.Vortrag anli4J3lich der Tagung der Fachgruppe "Makromolekulare Chemie" der Gesellxhati Deutsshrr Chemiker iiber "Kautschukelastische Polymersysteme" in Bad Nauheim vom 30. his 3 I . Marz I992

Multigraft Copolymers from an Upscalable Synthesis Route — Material Characteristics and Application Relevant Performance

“…systematically studied the variation of σ m as a function of PS‐content in trifunctional graft copolymers with PB backbones, graft molecular weight M n , PS − graft and the grafting density γ expressed in terms of the number of grafts per 20000 C‐atoms in the backbone. [ 8 ] It is shown for such graft copolymers with M n , PS − graft =8.3 kg mol −1 , σ m approaches a plateau above 20 grafts / 20000 C‐atoms in the backbone. Adapting the used relation to tetrafunctional PIPS‐multigraft copolymers results in the equation $$$$\begin{equation} \gamma _{PI} = \frac{2\beta _{avg} \cdot M_{n,I}}{5M_{n,PI-backbone}}\cdot 20000 \end{equation}$$$$Calculating γ for representative MGCPs according to Equation (), one gets γ = 6.8 and 5.8 for MIS‐4‐8.5‐8.5 and MIS‐4‐7.7‐15.1, corresponding to σ m ‐values of 15.7 and 16.4 N mm −2 , respectively.…”

“…[20] Frank et al systematically studied the variation of 𝜎 m as a function of PS-content in trifunctional graft copolymers with PB backbones, graft molecular weight M n, PS − graft and the grafting density 𝛾 expressed in terms of the number of grafts per 20000 C-atoms in the backbone. [8] It is shown for such graft copolymers with M n, PS − graft =8. For the MGCPs investigated in this work, 𝜖 b shows a maximum of 2000 % at about four branch points followed by a decrease until 𝛽 has reached nearly 8 (Figure 5b).…”

“…[6,7] Earlier activities in this field of multiple graft copolymer synthesis were concerned with the preparation of comb-like architectures, too, but problems of considerable amount of homo-PS in the final product and the degradation of the polydiene backbones had to be overcome. [8] For this, the anionic synthesis route turned out as the most suitable approach. Several synthesis activities are reported, changing either the nature of the elastic component (polybutadiene or polyisoprene), the location of the grafts along the rubbery backbone chain (randomly distributed or equally spaced) or the functionality of grafting/branch points.…”