Block copolymers domain formation

Meier D.J., Theory of block copolymers Domain formation in A-B block copolymers, J. Polym. Sci., Part C, 26, 81, 1969. 

An exhaustive, critical review of the status concerning current statistical thermodynamic analysis of block copolymer domain formation will not be presented here. A precis only of the major theories is given and the predictions from each noted, fuller details are available in the original publications. Furthermore, whilst the earlier theories of Meierand Williams " were important in stimulating interest and defining the questions to be addressed, they are not considered here since the more recent ideas encompass all the features of the earlier theories. 

A very special type of ABA block copolymer where A is a thermoplastic (e.g., styrene) and B an elastomer (e.g., butadiene) can have properties at ambient temperatures, such as a crosslinked rubber. Domain formations (which serves as a physical crosslinking and reinforcement sites) impart valuable features to block copolymers. They are thermoplastic, can be eaisly molded, and are soluble in common solvents. A domain structure can be shown as in Fig. 2. 

Inoue T., Soen T., Hashimoto T., and Kawai, H. Studies on domain formation of the A-B t3fpe block copolymer with polystyrene and polyisoprene. Macromolecules, 13, 87, 1970. 

Amino acid substitutions on the native y52 8sKIpeptide, coiled-coil domain of human fibrin were able to stabilize the coiled-coil formation. These substitutions were targeted to the positions that compose the interface between coiled-coil strands while the solvent-exposed residues were left unperturbed. This strategy aimed at reducing the likelihood of immunogenicity for future in vivo apphcafion of these materials. In contrast to PEG block copolymers with end blocks that are not used for directed assembly, PEG copolymers with coiled-coil protein motives aim to enhance intermolecular interactions and control over the assembly conditions [85, 173]. 

Formation of physical cross-links by the anchorage of chain ends in semicrystalline domains and production of permanent entanglements is shown in the HBIB block copolymers. No such arrangement exists for the inverted polymer HIBI. (No attempt has been made to show possible chain folding, or superstructure development of their... 

Figure 10. Illustration of influence of domain formation in block copolymers according to the models of Helfand and coworkers. The free energy is shown as a function of the size and separation of the domains of varying composition. (The spontaneous separations may be analogous to the way superstructure is formed in natural polymers of plants and animals.)...

The formation of a patterned surface through selective segregation of nanoparticles onto one domain of a block copolymer film can be used to produce complex 2-D nanoparticle arrays in a controlled fashion. However, the resulting... 

Fig. 2.56 Beating of Kiessig fringes observed using X-ray reflectivity from a PVP PS-PVP tri block copolymer film (fes = 0.48, Mv = 120 kg mol ) with two discrete thicknesses of 1935 and 2229 A (de Jeu et al. 1993). The difference in height results from island and hole formation at the free surface, and is equal to the bulk domain spacing.

For block copolymers with a polyacid or polybase block, the structure and properties of micellar solutions depend on the pH. For example, Morishima et al. (1982b) found that for a poly(9-vinylphenanthrene)-poly(methacrylic acid) (PVPT-PMA) diblock in water, the rate constant for the fluorescence quenching of phenanthrene groups by oxidative non-ionic quencher is pH dependent. These authors suggested that at low pH the polyacid units are not fully ionized and may participate in the formation of hydrophobic domains, cooperatively with PVPT. An alternative explanation is that the PM A chains are less solvated when... 

Phase separation and the formation of domains in blends and block copolymers results from the thermodynamic incompatibility of the constituents. The mixing of two phases is governed by the thermodynamic relation... 

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