SI diblock copolymer

We have studied three different lamellar polystyrene-Wock-polyisoprene (SI) diblock copolymers (see Table 1) with molecular weights of around 50 kg/mol using... 

FIGURE 13.15 Electron micrc raphs of SI diblock copolymer (MW = 524,000 g/mol, 52% styrene) at a free surface, (a) Lamellae oriented parallel to surface (typically observed), (b) Lamellae oriented perpendicular to surface (occasionally observed). The arrows indicate the locations of the free surfaces. (From Hasegawa and Hashimoto (1985) reprinted (adapted) with permission from ACS, copyright 1985.)... 

FIGURE 16 Electron micrographs of SI diblock copolymer (MW = 524,000g/mol, 52% styrene) at a free surface, (a) Lamellae oriented parallel to surface, (b) Lamellae oriented perpendicular to surface. 

In Figure 6b, domain periodicity D (= 27t/qmax) was plotted against 1/T. It is interesting to note that there exists a discontinuity in D at ODT. This is in contray to the results of Sakomoto and Hashimoto ° that D is continuous at ODT. Recentiy, however, Floudas and coworkers examined the ODT of SI2 simple graft copolymer, SIB terpolymer, (SI) star-block copolymers and asymmetric SI diblock copolymer using SAXS, and reported the discontinuity in D. Ogawa et al. also reported similar results to our study for an asymmetric SI diblock copolymer (fps=0.303). 

Fig. 28 Interfacial tension for the PS/I2S/PI systems as a function of the composition of the graft copolymers at a constant temperature of 140°C and constant 2 wt% copolymer added to the PS open circles), or to the PI phase (filled circles), or when 1 wt% was added to the PS and 1 wt% to the PI phases (black and white circle). Also shown are the interfacial tension data for PS/SI/PI at 140°C, i.e., with the addition of 2 wt% of the SI diblock copolymer to the PS (open inverse triangle), or to the PI phase (filled inverse triangle), or when 1 wt% was added to PS and 1 wt% to the PI phases black and white inverse triangle). The squares are the interfacial tension data for PS/S2I/PI at 140°C when 2 wt% of S2I was added to the PS phase (filled square) or to the PI phase (open square). The dashed line indicates the PS/PI interfacial tension in the absence of additives [56]...

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... 

Figure 8.5 The dependence of complex viscosity ( ri ) on angular frequency (< ) for a lamella-forming SI diblock copolymer having...

Parallel shift in log G versus log G" plots has also been observed in highly asymmetric SI diblock copolymers (Choi et al. 2003 Han et al. 2000) and in a highly... 

In this section, we present the effect of thermal history on the oscillatory shear rheometry of block copolymers. We will show that the occurrence of a minimum in G in the isochronal dynamic temperature sweep experiment does not necessarily signify OOT for highly asymmetric block copolymers instead, it sometimes reflects imperfect bcc spheres, as determined by SAXS and TEM, due to an insufficient annealing of a specimen. Here, we will show that a minimum in G, observed for an unannealed specimen in the isochronal dynamic temperature sweep experiment, may disappear completely when the specimen is annealed for a sufficiently long time at an elevated temperature below the TmoT of highly symmetric SI diblock copolymer. 

Figure 8.23 gives the tempa ature dependence of G during the isochronal dynamic temperature sweep experiments at > = 0.01 rad/s in the heating process for highly asymmetric SI diblock copolymer SI-7/29 (M = 3.6 x 10", — 1.03, —... 

Figure 8.23 Isochronal dynamic temperature sweep experiments for a highly asymmetric SI diblock copolymer SI-7/29 at = 0.01 rad/s during heating (O) before annealing and (V) after annealing at 95 °C for 15 days. (Reprinted from Yamaguchi et al., Macromolecules 32 7696. Copyright 1999, with permission from the American Chemical Society.)...

Figure 8.27 Log G versus log G" plots for an SI diblock copolymer SI-Z after different thermal treatments (O) as-cast specimen without thermal treatmenf (A) as-cast specimen after being annealed at 80 °C for 1 week, and ( ) as-cast specimen after being annealed at 80 °C for 2 weeks. AU measurements were carried out at 80 °C. (Reprinted from Hashimoto et al.. Polymer 39 1573. Copyright 1998, with permission from Elsevier.)...

Choi and Han (2004) carried out an experimental study to address some of the questions posed above. In so doing, they employed eight low-molecular-weight, nearly symmetric SI diblock copolymers, to investigate the molecular weight dependence of r]Q in the disordered state (at T > For this, they first determined the of... 

Table 8.1 Molecular characteristics, glass transition temperatures, and order-disorder transition temperature of the SI diblock copolymers... 

The values of in Figure 8.34 were obtained from the logarithmic plots of reduced complex viscosity ( )], . ) versus Ojco for the eight SI diblock copolymers in the disordered state, for which values of were determined by shifting the log G" versus log CO plots along the co axis using T. = T p + 104 °C as the reference temperature. 

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