AB-type block copolymers

In three dimensions, Ohta and Kurokawa [32] reported that a BCC arrangement was only slightly more favored than the FCC arrangement. In fact, many BCC structures have been reported for AB type block copolymers and the blends of homopolymer-block copolymer systems [27,33-35]. However, the lattice structure of the core-shell type polymer microspheres was FCC. This FCC formation resulted in the lower viscosity of... 

The chain arrangement of this morphology was schematically proposed as in Fig. 10. The cell of the microsphere has a hexagonal surface, and the AB diblock copolymers form a bilayer between the microspheres. From this schematic arrangement, the optimal blend ratio of the AB block copolymer in this system was calculated as 0.46. This value was very close to the blend ratio of the AB type block copolymer 0.5 at which the blend showed the hexagonal packed honeycomb-like structure. 

The morphology obtained from the blend of the core-shell type microspheres and AB type block copolymers with spherical morphology is shown next [37]. Figure 12 shows the typical morphologies of the blend ob-... 

Vinyl polymerization initiated by macroinitiator yield AB, ABA, or (AB) types block copolymers. Macroinitiators such as macrobis peroxides, polyazoesters, and... 

ABA-type triblock copolymerization of MMA/BuA/MMA should give rubberlike elastic polymers. The resulting copolymers should have two vitreous outer blocks, where the poly(MMA) moiety (hard segment) associates with the nodules, and the central soft poly(BuA) elastomeric block provides rubber elasticity. Ihara et al. [35] were the first to synthesize an AB-type block copolymer, with MMA (190 equivalents of initiator) first polymerized by... 

Monofunctional Iniferter R-X > R-tMJj-X End-functional polymer, AB-type block copolymer... 

This polymer was shown to give an AB-type block copolymer when used as initiator for the subsequent polymerization of vinyl chloride. 

A number of statistical thermodynamic theories for the domain formation in block and graft copolymers have been formulated on the basis of this idea. The pioneering work in this area was done by Meier (43). In his original work, however, he assumed that the boundary between the two phases is sharp. Leary and Williams (43,44) were the first to recognize that the interphase must be diffuse and has finite thickness. Kawai and co-workers (31) treated the problem from the point of view of micelle formation. As the solvent evaporates from a block copolymer solution, a critical micelle concentration is reached. At this point, the domains are formed and are assumed to undergo no further change with continued solvent evaporation. Minimum free energies for an AB-type block copolymer were computed this way. 

Komiya et al. described the living ROMP synthesis of AB-type block copolymers that contain side chain liquid crystalline polymer blocks and amorphous blocks [62]. Norbornene (NBE), 5-cyano-2-norbornene (NBCN) and methyl-tetracyclododecene (MTD) were used for the amorphous polymer blocks, while I-n (n=3,6) were used for the SCLCP block (see Fig. 9). Initiator 1 was used for the ROMP. Block copolymers with monomer ratios from 75/25 to 20/80 (amor-... 

Block copolymers serve as blending agents with simple homopolymers as well as stabilizing agents for mixtures of homopolymers. Blends of a homopolymer with an AB-type block copolymer will be weak if the elastomeric segment of the block polymer forms the sole continuous phase or one of the continuous phases. 

Endo and Tomita reported the copolymerization of allene with isocyanide [135, 141] and with 1,3-butadiene [142] to form AB-type block copolymers. The Pt-catalyzed hydrosilylation reaction of poly(allene-Msocyanide) occurs selectively at the C=CH2 group of the allene monomer unit to produce the polymer with silyl pendant groups (Eq. 38) [135]. The allene macromonomer... 

While the morphology of AB-type block copolymers is limited to a relatively small number of possibilities, the morphology of ABC triblock copolymers is considerably richer and complex (Bates and Fredrickson, 1999). New, exotic, and often unexpected phases are continually being discovered by ex-perimentahsts (Breiner et al., 1998). There is a need for theoretical methodology that is capable of predicting, a priori, the possible new morphologies in these more complex block copolymers. We describe one such method in this article. 

The order of monomer addition is important. For example, to prepare an AB type block copolymer of styrene and methyl methacrylate, st ene must be polymerized first using a monofunctional initiator and when styrene is completely reacted, the other monomer MMA must be added. The copolymer would not form if MMA were polymerized first, because living poly(methyl methacrylate) is not basic enough to add to styrene. The length of each block is determined by the amount of corresponding monomer which was provided. To produce ABA type copolymer by monofunctional initiation, B can be added when A is consumed, and A added again when B is consumed. This procedure is possible if the anion of each monomer sequence can initiate polymerization of the other monomer. Multiblock copolymers can also be made in this way. 

A living AB-type block copolymer made by monofunctional initiation can be terminated with a bifunctional coupling agent like a dihaloaUcane to make a triblock copolymer. For example, an ABA triblock copolymer can be made as follows ... 

A polymeric micelle is a macromolecular assembly that forms from block copolymers or graft copolymers, and has a spherical inner core and an outer shell (1). As shown in Fig. 1 in which an AB type block copolymer is used, a micellar structure forms if one segment of the block copolymer can provide enough interchain cohesive interactions in a solvent. Most studies of polymeric micelles both in basic and applied aspects have been done with AB or ABA type block copolymers... 

Figure 23 Synthetic scheme of AB-type block copolymer brushes composed of a POEGMA block and a PHEMA block. Reprinted from Ishizu, K. Satoh, J. Sogabe, A. J. Colloid Interface Sci. 2004, 274 (2), 472-479, with permission from Elsevier.

Figure 8.11 Phase diagram for the geometry, stability and microdomains of an AB-type block copolymer.

Reineke and coworkers established the synthesis of AB type block copolymers comprised of a glycopolymer block and a cationic block via aqueous RAFT polymerization of 2-deo)qr-2-methactylamido glucopyranose and the primary amine-containing iy-(2-aminoethyl) methaciylamide. The cationic block functions as a non-viral vector to complex DNA or siRNA and... 

The block copolymers formed by lamella surface modification would be expected to be less crystallizable than the parent polymer. It is possible that crystallization with the same lamellar thickness as obtained for the parent polymer could occur. However, thinner and thicker lamellas would only form with difficulty, due to the chemical modification of the preexisting surfaces. However, the domain structure reported for ABA and AB type block copolymers are not expected in the (AB)n type, discussed herein. 

Fig. 1.13 Theoretical and experimental phase diagrams for an AB-type block copolymer melt left-hand figure reproduced from Matsen (2012) and the right-hand figure from Matsen (2002))...

Matsen MW (2012) Effect of architecture on the phase behavior of AB-type block copolymer melts. Macromolecules 45(4) 2161-2165... 

Monge and Haddleston [39] reported on online NMR in the analysis of poly(n-hydroxy-snccinamide methacrylate)-6 poly(methyl methacrylate AB) type block copolymers. 

AB-type block copolymers can be synthesized by adding a second monomer (B) to preformed polyvinylterrocene anion (A), wdiich was synthesized as described above. Styrene, methyl methacrylate, and propylenesulfide have been appbed as monomer B. Typical results are given in Tab. 15.2 and Fig. 15.8. 

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