SB diblock copolymer

A detailed study of SB diblock copolymers and diblock/homopolymer blends was conducted in the range of composition in which the polybutadiene cylindrical morphology prevails Stress-strain experiments on a series of samples revealed dramatically varying behavior from essentially brittle response to substantial and attractive levels of toughness. Figures 2a to 2d provide representative stress-strain curves for the initial morphologies shown in Figs. 3a-3d. Table 1 provides the relevant molecular level information for these blends. 

With increasing amoimt of triblock copolymer, blends of lamellar SBT triblock copolymers with the asymmetric SB diblock copolymer form core-shell spheres, core-shell cylinders, core-shell double gyroids, and lamellae (Fig. 34). T forms the core domains in these morphologies, which can be considered as coreshell analogues of the well-known diblock copolymer morphologies (76). 

Pioneering works on the micromechanical deformation mechanisms in block copolymers date back to the mid-eighties when cavitation mechanism in styrene-butadiene (SB) diblock copolymers containing PB cylinders in a PS matrix was proposed (52,53). Based mainly on tern investigations, a two-step craze growth mechanism was proposed ... 

SAXS measurements have also been useful in studies of the morphology and phase behavior of block copolymer/homopolymer blends. SAXS data on PS blends with SB diblock copolymers showed the presence of microdomains, which disappeared as the order-disorder transition was approached with increased temperature [162]. The order-disorder transition and the order-order transition (change in gyroid to cylinder morphology) was investigated with SAXS for PS/SI diblock copolymer blends [163]. The interfacial thickness of PS/PMMA samples with... 

Kraton 1102 contains about 20 wt % uncoupled SB diblocks. This is because a coupling method was used to produce SBS triblock copolymer from SB diblock copolymer that was synthesized, via anionic polymerization, using a monofunctional initiator. 

Although Burger et al. [65] showed that the polydispersity effect can extend the validity of the F-H analysis to values of N lower than lO, the fluctuation contribution to the total would be unacceptably very large for most SI and SB diblock copolymers, for instance, which have N 10 [66, 67]. 

Table 19.3 Typical reaction conditions for the hydrogenation of polybutadiene (PB), styrene-butadiene diblock copolymer (SB), styrene-butadiene-styrene triblock copolymer (SBS) and nitrile butadiene rubber (NBR).

The experimental studies on phase behavior and pattern formation reviewed here have been done on substrate-supported films of cylinder-forming polystyrene- foc -polybutadiene diblock (SB) [36, 43, 51, 111-114] and triblock (SBS) [49, 62, 115-117] copolymers (Table 1), lamella-forming polystyrene- /ocfc-poly(2-vinyl pyridine) diblock copolymers (SV) [118, 119] and ABC block terpolymers of various compositions [53, 63, 120-131], In simulation studies, a spring and bid model of ABA Gaussian chains has been used (see Sect. 2) [36,42, 58, 59],... 

A Study of the Flow Properties of a Styrene-Methylmethacrylate Diblock Copolymer and SBS Triblock Copolymers... 

Linear low-density polyethylene (LLDPE) and PS resins were the same as described previously (Chapter 21). The various block copolymers that were used as compatibilizers have also been described (I). A series of crystalline copolymers (Q series) was prepared by hydrogenation of diblock and triblock copolymers of styrene and butadiene [styrene-hydrogenated butadiene (SEB) and styrene-hydrogenated butadiene—styrene (SEBS)J (1). Triblock copolymers of styrene and butadiene [styrene-butadiene-styrene (SBS)] and a noncrystalline hydrogenated block copolymer (SEBS) (Kraton) were supplied by Shell Chemical Co. Diblock copolymers of styrene and butadiene [styrene-butadiene (SB) (Vector)] were obtained from Dexco Polymers. The characteristics of the resins are given in Table I. 

Multi-block copolymers can form a greater variety of ordered phase structures than diblock copolymers, via self-assembly. Some of them have been widely applied as the matrix materials, such as styrene-butadiene-styrene (SBS) thermal elastomers, acrylonitrile-butadiene-styrene (ABS) copolymers and polyurethanes. 

Vector SBS, SIS, and SB styrenic block copolymers are produced as diblock-free and diblock copolymers. The company s process to make linear SBCs yields virtually no diblock residuals. Residual styrene butadiene and styrene isoprene require endblocks at both ends of the polymer in order to have a load-bearing segment in the elastomeric network.2 However, diblocks are blended into the copolymer for certain applications. Vector SBCs are injection-molded, extruded, and... 

Figure 1. Viscosity curves of various styrene copolymers at 100°C. SEES, SBS, and SIS are styrene triblock copolymers, SBR706 is styrene diblock copolymer, and IR2200 is polyiso-prene homopolymer [31].

SB (styrene-butadiene) diblock copolymer (about 50/50 composition) ... 

The second order reflections (not shown here) are not wliolly suppressed as expected theoretically for symmetrical diblock copolymers. This effect can be explained by the slight asymmetry of the block length (in particular when the volume fraction is taken into account) leading to different thicknesses of the PS and PB rich domains, respectively. Both, second and third order reflections are at double and triple values of q within an error smaller than 2% confirming that the system is lamellar. The higher order maxima appear only in the phase separated state and vanish close to Tmst- Their existence indicates that the spatial concentration profile differs from a sinusoidal shape, which is expected to be true in particular in the sb ong segregation limit (SSL). 

Early morphological studies to determine the nature of multiphase polymers and blends were reviewed by Folkes and Keller [363]. Many studies were of extruded block copolymers of materials such as SBS where the dispersed phase, an unsaturated rubber stained with OSO4 (see Section 4.4.2), was observed in the form of spheres, cylinders, or lamellae [364]. An excellent example is shown in a TEM micrograph of a thin section of a poly(styrene-butadiene) diblock copolymer, stained with OSO4 [365], which depicts the (100) projection of a body centered cubic lattice (Fig. 5.79). 

Li S, Myers SB, Register RA. Sohd-state structure and crystallization in double-crystalline diblock copolymers of linear polyethylene and hydrogenated polynorbomene. Macromolecules 2011 44 8835-8844. 

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