Upper critical order-disorder transition

Oscillatory Shear Rheometry of Microphase-Separated Block Copolymers Exhibiting Upper Critical Order—Disorder Transition Behavior... 

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]. 

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... 

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... 

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. 

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... 

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