Upper order-disorder temperature

For example, 0 describes the temperature dependence of composition near the upper critical solution temperature for binary (liquid + liquid) equilibrium, of the susceptibility in some magnetic phase transitions, and of the order parameter in (order + disorder) phase transitions. 

Reactive compatibilization can also be accomplished by co-vulcanization at the interface of the component particles resulting in obliteration of phase boundary. For example, when cA-polybutadiene is blended with SBR (23.5% styrene), the two glass transition temperatures merge into one after vulcanization. Co-vulcanization may take place in two steps, namely generation of a block or graft copolymer during vulcanization at the phase interface and compatibilization of the components by thickening of the interface. However, this can only happen if the temperature of co-vulcanization is above the order-disorder transition and is between the upper and lower critical solution temperature (LCST) of the blend [20]. 

Fig. 2.51 Effect of reciprocating shear (strain amplitude, k = 200%) on the ODT of an /pep = 0.55 PEP-PEE diblock (Koppi etal. 1993). Here y denotes the shear rate.The equilibrium order-disorder transition (, A) and disordered state stability limit (A.O) are shown. The upper curve is a fit to the scaling relation Tom y2- The lower curve represents the. scaling rs(A) A-i,3Todt> where A = y/y, with y an adjustable, parameter. Points given by and O were obtained at fixed temperature by varying y, while those represented by A and A were determined by varying the temperature at fixed y.

For most BC the phase diagram is characterized by the presence of an upper critical solution temperature, UCST, also known as an order-disorder transition temperature or a microphase separation temperature. Below UCST the block copolymers phase separate, while above it, an isotropic melt is obtained. Owing to the chemical... 

Fig. no. Phase diagram of the submonolayer In/Ge(l 11) system as determined using RHEED observations [8111]. Except for the order-disorder transitions to the high-temperature 1x1 structure, all transformations are irreversible, i.e. only structural changes from lower to upper structure are observed. The subsequent STM observations [96G4] confirmed the formation of all... 

Two-component block copolymers commonly display upper critical solution temperature (UCST) behavior [7]. They form ordered, microphase-separated morphologies at lower temperatures but ean be heated to temperatures where the discrete heterogeneity is lost. The transition point from a heterogeneous microstructure to a compositionally homogeneous state is termed the order-to-disorder transition (Eqdt)- At any given degree of polymerization N, the highest Eqdt exists in systems with equal volumes of the two components, at... 

The order-to-disorder ttansition between ordered phases and the disordered phase have been investigated for a number of block copolymers in order to check the theoretical predictions. Besides the influence of temperature, some studies applying pressure were carried out. It was shown that high pressure can suppress the increase of compositional fluctuations and, therefore, stabilize a disordered phase. While most block copolymers show an upper critical solution temperature (orupper order-to-disorder ttansition), for PS-b-PPMA diblock copolymers a closed loop miscibility gap was found, which increases with increase of molecular weight. ... 

The morphology and micro-domain structure is dependent on temperature and process conditions. Hashimoto and Balsara have shown that the order-order and order-disorder transitions are profoundly influenced by sample preparation and thermal history . In block copolymers showing upper critical solution temperature (UCST) behavior, it has been observed that the d-spacing scales as d where, T is absolute temperature. This effect is attributed to the change in interaction parameter (j) (i.e. X decreases with increase in temperature) Process conditions such as sample preparation, annealing and quench depth (during melt processing) affect the... 

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