Crystalline Morphology of Block Copolymers

The miscible blends consisting of two crystalline homopolymers may form unique morphologies in the system, and several studies have been reported [62-67]. However, very few such blends are miscible, so that information on the crystalline morphology formed in crystalline/crystalline polymer blends is very limited. 

It is widely recognized that amorphous-amorphous diblock copolymers form a variety of microdomain structures when the segregation strength between different blocks is moderately large. When one block is crystalline and the other is amorphous (i.e., crystalline-amorphous diblock copolymers), it is easily supposed that the morphology formation at low temperatures is driven by a close interplay between 

When both blocks are crystalline, the morphology formation is more complicated because two kinds of crystallization, as well as microphase separation, intervene during morphology formation. It is useful to summarize this morphology formation in terms of a difference in the crystallizable temperature 7), of both blocks (Fig. 10.8). When of one block is considerably higher than that of the other block, two crystallizations occur almost independently (two-step crystallization). That is, the crystallization of higher 7), blocks 

Lamellar crystal Amorphous layer Lamellar crystal 

Crystalllzable temperature Nucleatlon rate Growth rate Other factors 

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In this chapter, we first summarize the crystalline morphology formed in homopolymers, which is usually explained in many textbooks of polymer science. Next, we describe more complicated morphology, that is, the crystalline morphology of block copolymers. This subject is relatively new as compared with that of homopolymers, so that it is not fully understood at present. 

Crystalline Morphology of Block Copolymers with Glassy Amorphous Blocks... 

Typical phase morphologies of block copolymers are illustrated in Figs. 5.38 0 and 5.79. In the classification of phases, the phase-separated block copolymers are considered to be amphiphilic liquid crystals despite the fact that inside the phase areas the typical liquid-crystalline order is missing (see Sect. 5.5). In this section the question will be addressed what happens when the usually micro- or nano-phase separated block copolymers show solubility, i.e., when the amphiphilic liquid crystal becomes thermotropic, i.e., dissolve at a given temperature. 

It was the objective of this work to investigate the effect of variation in block architecture (number and the order of the blocks) on the crystallinity level, morphology, the stress-strain and hysteresis behavior of this series of polymers. In addition, the composition ratio of the two block types is expected to play a crucial role in determining the bulk material properties of the block copolymers. This is related to the fact that the mechanical properties of block copolymer are typically influenced more substantially by the behavior of the continuous phase, as will be demonstrated.(1,22)... 

A list of previous books and reviews on block copolymers is given in the bibliography. There have been no authored books in the field since the volume by Noshay and McGrath in 1977, and this was primarily concerned with the chemistry and materials science. Most of the literature consists of outdated edited books, although a number of review articles have appeared recently. The field has advanced rapidly during the last two decades, with major new theoretical developments, discoveries of new morphologies and the initiation of research in new fields such as thin films, crystalline solids and gels in concentrated solutions. It is thus hoped that this book is timely and fulfils the need for an up-to-date summary of the fundamental physics of block copolymers. 

Thermodynamic treatments of block copolymer morphology, such as those of Helfand (1,2,3) and Meier (4), which are based on anionically polymerized, monodisperse segment AB and ABA type block copolymers, are not applicable in the present case. The large number of short segments in each molecule, the possibility of crystallinity in one or both phases, and the likelihood of metastable morphologies work together to preclude the analytical approaches presently available. 

Block copolymers, particularly of the A-B-A type, can exhibit properties that are quite different from those of random copolymers and even from mixtures of homopolymers. The physical behavior of block copolymers is related to their solid state morphology. Phase separation occurs often in such copolymers. This can result in dispersed phases consisting of one block dispersed in a continuous matrix from a second block. Such dispersed phases can be hard domains, either crystalline or glassy, while the matrices are soft and rubber-like. 

CrystaUization represents an alternative means of firmly holding block copolymers in a cylindrical morphology. Polymeric cyhnders based on the simultaneous CrystaUization of block copolymers with a preferential 1-D self-assembly process in solution have been reported, where the crystalline block acts as a solid ribbon-hke backbone and the other blocks act as side chains covalently bonded with the core. The crystaUine core is stable against various stimuli, provided that... 

In addition, the self-assembly of block copolymers has provided a promising alternative for the synthesis of analogs of molecular bmshes, in which a cross-linked or crystalline cylindrical (micro)domain instead of a linear polymer backbone acts as the backbone. These assemblies have the characteristic worm-like morphology at a similar nanosize scale as molecular bmshes. In this chapter, the polymeric cylinders assembled from block copolymers are briefly discussed as a complement of molecular bmshes (Section 6.06.2.6). Different synthetic strategies and polymerization techniques are reviewed to illustrate specific advantages and limitations. Particular attention is paid to syntheses employing CRP techniques, as these have proven especially useful in the preparation of well-defined functional molecular bmshes (Figure 1). 

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