Blends of block copolymers

In block copolymers (BCPs), the frustration of chains offered by the covalent connectivity of the blocks prevents them from undergoing macrophase separation on a large scale, and this induces a microphase separation of the blocks resulting in the formation 10-100 nm scale periodic structures with different shapes and geometries (depending on the fraction / of the component copolymers and the product yN) viz., lamellar, hexagonal closed pack (HCP), body-centered cubic 

The morphology of alternate crystalline and amorphous layers in PCL-b-PB copolymers is more complicated, however, than of those found in the case of miscible crystalline/crystalline homopolymer blends (with a large crystallization rate asymmetry). In the case of the former, a covalent connectivity of the amorphous and crystalline blocks prevented a macrophase separation or complete rejection of the amorphous blocks from the crystalline region/blocks. The SAXS curves obtained during the melting (or crystallization) transformations in the PCL-b-PB 

Time-Resolved Studies Kinetics of Crystallization and Melting 

This chapter has provided a brief presentation of the underlying theories, and the analytical tools and techniques used to characterize polymer blends by X-ray scattering (SAXS and WAXS). The text was not aimed at reviewing the studies conducted with all types of polymer blends - that is, miscible versus immiscible 

Finally, the advent of synchrotron-mediated (intense) sources of X-rays has led to dramatic improvements in the study of dynamics and transient processes such as crystallization in polymer blends. Moreover, the capability of measuring nanoscale dimensions via small-angle scattering will have great potential for future investigations of nanostructured materials and devices. 

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Blending of Block Copolymers with Hydrogen Bonding Interactions. 201... 

Abstract This chapter gives an overview of the research on the self-assembly of amorphous block copolymers at different levels of hierarchy. Besides the influence of composition and topology on the morphologies of block copolymers with linear, cyclic and branched topologies blends of block copolymers with low molecular weight components, other polymers or block copolymers and nanoparticles will also be presented. 

Binary blends of block copolymers can also macrophase separate if the mismatch in molecular weights is sufficient. In the other limit, blends of diblocks of... 

This chapter is organized as follows. Section 6.2 is concerned with experiments on binary block copolymer/homopolymer blends, Section 6.3 deals with experiments on ternary blends containing a block copolymer and in Section 6.4 experiments on binary blends of block copolymers are reviewed. Theory for the corresponding type of blend is discussed successively in Sections 6.5 to 6.7. Finally, experiments on thin films are discussed in Section 6.8, separately from the work on bulk blends, in keeping with earlier chapters. 

Experiments on blends of block copolymers with two homopolymers... 

Until recently, very little quantitative information was available on blends of block copolymers. The literature is summarized in Table 6.3. Hoffman et al. (1970) reported microscopic demixing of blends of PS-PB diblocks, with two maxima in the domain size distribution, but with no evidence tor macrophase separation. These findings must be treated with caution in the light of more recent results. Hadziioannou and Skoulios (1982) used SAXS and SANS to investigate the morphology of binary blends of PS-PI diblocks, and binary PS-PI/PS-PI-PS or PS-PI/PI-PS-PI blends or blends of the two types of triblock. They found that the blends were microphase separated, and that the sharpness of the interface was not reduced in blends compared to neat copolymers. The transition between a lamellar and a cylindrical structure was shown to depend primarily on blend composition. In contrast, the transition from a lamellar to a disordered phase at... 

Volker Abetz, T.G. "Formation of superlattices via blending of block copolymers". Macromol. Rapid Commun. 21(1), 16-34 (2000). 

Then we will turn our attention to blends of block copolymers where the self-assembly is dominated by multiple hydrogen bonding between complementary blocks of the two constituents. The self-assembly of some of these systems has features in common with that of star copolymers and allows one to study the consequences of this architecture for the structures formed [43-45]. 

T. Hashimoto, K. Yamasaki, S. Koizumi, H. Hasegawa, Ordered structure in blends of block copolymers. 1. miscibihty criterion for lamellar block copolymers. Macromolecules 26 (1993) 2895-2904. 

D. Yamaguchi, M. Takenaka, H. Hasegawa, T. Hashimoto, Macro- and microphase transitions in binary blends of block copolymers with complementarily asymmetric compositions, Macromolecules 34 (2001) 1707-1719, http //dx.doi.org/10.1021/ma0013152. 

N.Y. Vaidya, C.D. Han, Temperature-composition phase diagrams of binary blends of block copolymer and homopolymer. Polymer 43 (2002) 3047-3059. 

K.A. Orso, RF. Green, Phase behavior of thin film blends of block copolymers and homopolymers changes in domain dimensions. Macromolecules 32 (1999) 1087-1092. 

V. Abetz, T. Goldacker, Formation of superlattices via blending of block copolymers, Macromolecular Rapid Communications 21 (2000) 16-34. 

There has been considerable general interest in blends of block copolymers with one homopolymer which is chemically identical with one block of the copolymer. Two such systems have been reported for blends of PCL with block copolymers in which one block is PCL. 

More recently, blends of block copolymers and crystalline polymers have been developed by Davison and Gergen. The block copolymers are based on hydrogenated styrene-butadiene-styrene triblock materials, known as styrene-ethylene butylene-styrene (SEES) triblock copolymers. The crystalline polymers are polyamides or thermoplastic saturated polyesters. ... 

In blends of block copolymer with homopolymer, there is an interplay between macrophase separation (due to the presence of homopolymer) and microphase separation (of the block copolymer). Which effect predominates depends on the relative lengths of the polymers and on the composition of the blend. 

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