Block copolymers disordered state

Microdomain stmcture is a consequence of microphase separation. It is associated with processability and performance of block copolymer as TPE, pressure sensitive adhesive, etc. The size of the domain decreases as temperature increases [184,185]. At processing temperature they are in a disordered state, melt viscosity becomes low with great advantage in processability. At service temperamre, they are in ordered state and the dispersed domain of plastic blocks acts as reinforcing filler for the matrix polymer [186]. This transition is a thermodynamic transition and is controlled by counterbalanced physical factors, e.g., energetics and entropy. 

Fig. 59 Phase diagram for blend consisting of two symmetric PS-6-PI block copolymers of different molecular weights in parameter space of temperature and fraction of higher molecular weight copolymer, . disordered state lamella A PS cylinder. From [179]. Copyright 2001 American Chemical Society... 

Stepanek, P. and Lodge, T. P. (1996). Light scattering by block copolymer liquids in the disordered and ordered state. In Light scattering. Principles and development, (ed. W. Brown). Oxford University Press, Oxford. 

Jain S, Gong X et al. (2006) Disordered network state in hydrated block-copolymer surfactants. Phys Rev Lett 96 138304/1... 

Figure 13.13 Reduced storage modulus G and dynamic viscosity rj = G /w as functions of reduced frequency uto) for a cylinder-forming polystyrene-polybutadiene-polystyrene triblock copolymer with block molecular weights of 7000-43,000-7000. The curves are time-temperature-shifted to a reference temperature of 138°C the open symbols were obtained in the low-temperature ordered state the closed symbols were obtained in the high-temperature disordered state. (From Gouinlock and Porter 1977, reprinted with permission from the Society of Plastics Engineers.)...

Figure 13.20 Master curves of G Tq/T ) versus reduced frequency ajco for the PS-PI block copolymer described in Fig. 13-15 in the high-temperature disordered state and in the low-temperature ordered state flow-aligned into either the parallel or perpendicular directions. The arrows show the time-temperature-shifted frequencies at which the parallel (sideways arrow) and perpendicular (up arrow) orientations are achieved by large-amplitude shearing. The frequency ajcoc 300 secri is the reduced frequency below which G in the disordered and quenched states no longer superpose. (Reprinted with permission from Patel et al., Macromolecules 28 4313. Copyright 1995, American Chemical Society.)...

Figure 13.21 Apparent moduli G (closed symbols) and G" (open symbols) as functions of frequency at a strain amplitude of 10% for (a) a PS-PI lamellar block copolymer and (b) a smectic-A liquid crystal, 8CB. In both (a) and (b), the curves labeled MD are macroscopically disordered, or unaligned, states...

Because of the softness of interactions in block copolymers (here we restrict our consideration to flexible molten blocks above the glass transition temperature), thermal fluctuation in these systems is expected to be significant, especially near the order-disorder transition temperatures (Fredrickson and Helfand, 1987). In addition, the long relaxation times, due to the slowness of the motion of polymers, often lead to metastable and other kinetic states. Thus, full understanding of the self-assembly in block copolymers requires understanding of the nature of fluctuation, metastability, and kinetic pathways for various transitions. Most of this article is focused on theoretical studies of these issues in the simpler AB block copolymers. A key concept that emerges from these studies is the concept of anisotropic fluctuations first, these fluctuations determine the stability limit of an ordered phase second, they are responsible for the emergence of new structures... 

Other possible areas of application of the periodic surfaces, or of disordered relatives of these, include structure of superconductors in the intermediate state (Shal nikov 1941), sintering kinetics (Hench and Ulrich 1984), fluid flow through porous media (e.g., Zick and Homsy 1982), the topology of spacetime at the scale of Planck length (Wheeler 1957), the structure of the prolamellar body in certain plastics (Gunning 1965), certain phase-segregated block copolymers (Thomas et al. 1986 Anderson and Thomas 1988)) semiconductor-... 

In contrast to the situation found for dilute solutions, the behavior of nonlinear block copolymers in the solid state seems to have attracted great attention. Many theoretical publications appeared in recent years, dealing mainly with the phase behavior of star-block, simple graft and comb copolymers. Issues like the nature of the phase diagram and the order-disorder transition have been studied in considerable detail. The compatibilizing effects of complex copolymers, in comparison to simple diblock copolymers, were also investigated. 

The soluble blend system is a single phase material in which two components (such as two polymeric species or a polymer and a solvent) are dissolved molecularly as a homogeneous solution in the thermodynamic sense. A miscible polymer blend, a block copolymer in a disordered state, and a polymer solution are examples. Whether a homogeneous solution of this kind is regarded as a soluble blend system or as a dilute particulate system discussed above is often simply a matter of viewpoint. When there is a dilute solution of polymer molecules in a solvent and the focus of interest is the size and shape of the polymer molecules, the theoretical tools developed for the dilute particulate systems are more useful. If, on the other hand, the investigator is interested in the thermodynamic properties of the solution, the equations developed for the blend system are more appropriate. 

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