Crystallizable phase

A completely different behavior is reported for blends in which the crystallizable phase is dispersed. Fractionated crystallization of the dispersed droplets, associated with different degrees of undercooling and types of nuclei is the rule. The most important reason is a lack of primary heterogeneous nuclei within each crystallizable droplet. An important consequence of fractionated crystallization may be a drastic reduction in the degree of crystallinity. 

However, for polymer blends in which the crystallizable phase is dispersed into fine droplets in the matrix, crystallization upon cooling from the melt can sometimes occur in several steps (fractionated crystallization) that are initiated at different undercooling, often ending up with a crystallization at the homogeneous crystallization temperature T, [Aref-Azar et al., 1980 Bailtoul et al., 1981 Ghijsels et al., 1982 Santana and Muller, 1994]. 

Binary Polymer Blends Containing Two Crystallizable Phases. 410... 

A large number of polymer blends consists of two crystallizable phases (Table 3.15) hence, more studies have been carried out on the thermal behavior of crystalline/crystalline polymer blends. 

Many new materials or devices are produced in the micron or the nano scale. Therefore, if they can crystallize, the materials employed have to nucleate and crystallize within the designed microdomains (MDs). We will refer to isolated crystallizable phases in general terms as MDs even though depending on the material, these phases can have nano-scale confinement in one, two or three dimensions (e.g., lamellae, cylinders, or spheres). Confinement usually implies dispersion of a crystallizable phase into many MDs. 

Confined crystallization is a phenomenon that occurs in droplet dispersions, polymer blends, block copolymers, and thin films. Confinement has many consequences on the nucleation and crystallization behavior. Among the most notorious are the production of fractionated crystallization and the possibility of isolating crystallizable phases whose nucleation may be very different heterogeneous, superficial, or homogeneous nucleation. In specific cases confinement can also lead to crystal modifications for polymorphic polymers. 

For rigid-chain crystallizable polymers, spontaneous transition into the nematic phase is accompanied by crystallization intermolecular interactions should lead to the formation of a three-dimensional ordered crystalline phase. 

The rate of 7-radiation-induced cross-linking in the crystalline and amorphous regions of a crystallizable polychloroprene has been measured by Makhlis et al. [75] who have found a considerably lower cross-link density and less degradation in the crystalline portion of the rubber. The cross-links have been posmlated to be mainly intramolecular in crystalline regions and intermolecular in the amorphous phases. 

Fluconazole was shown to be crystallizable in the form of a monohydrate and as a 1/4 ethyl acetate solvate, as well as a new nonsolvated form [56], In the hydrate phase the water molecules were established as isolated sites, while the ethyl acetate molecules occupied constricted channels in its phase. In all of the structures, the fluconazole molecule adopted a common overall conformation, but one that was capable of some degree of flexibility. Hydrogen-bonding effects were deduced to be dominant in determining the structure of the different solvatomorphs. 

Since excellent reviews on block copolymer crystallization have been published recently [43,44], we have concentrated in this paper on aspects that have not been previously considered in these references. In particular, previous reviews have focused mostly on AB diblock copolymers with one crystal-lizable block, and particular emphasis has been placed in the phase behavior, crystal structure, morphology and chain orientation within MD structures. In this review, we will concentrate on aspects such as thermal properties and their relationship to the block copolymer morphology. Furthermore, the nucleation, crystallization and morphology of more complex materials like double-crystalline AB diblock copolymers and ABC triblock copolymers with one or two crystallizable blocks will be considered in detail. 

Polymers that are not crystallizable in the bulk phase, or only very weakly crystal lizable, are not so well understood. 

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