ABC linear triblock

We have further studied the synthesis of novel ABC linear triblock copolymers. Specifically, novel glassy(A)-fo-rubbery(B)-fo-crystalline(C) linear tri-... 

Tang P, Qiu F, Zhang H et al (2004) Morphology and phase diagram of complex block copolymers ABC linear triblock copolymers. Phys Rev E Stat Nonlin Soft Matter Phys 69 031803... 

Adding C block, a third component, to the end of an AB diblock copolymer produces an ABC linear triblock terpolymer. The syntheses of ABC triblock terpolymers in good quality are not so easy because each step of the sequential living polymerization of A, B and C monomers contains a chance to produce byproducts such as homopolymers and AB diblock copolymers that contaminate the system. This may be one of the reasons why the number of systems studied on ABC triblock terpolymers is much smaller than that on AB diblock copolymers. Another reason is that the number of parameters that defines the mesoscopic organizations of block copolymers increases dramatically just by adding another component to diblock copolymers. Whereas an AB diblock copolymer is defined by three parameters, (/>a, Xab and A, a triblock terpolymer consisting of A, B and C blocks requires six parameters, (/>a, b = a b) ... 

Sun, M., Wang, P., Qiu, E et al. (2008) Morphology and phase diagram of ABC linear triblock copolymers Parallel real-space self-consistent-field-theory simulation. Physical Review E, 77,016701. 

Scheme 21.9 Reaction pathways yielding to the different linear, cyclic and bicyclic structures during t e en to-en eye ization of an ABC linear triblock copolymer, bearing A and C sequences with antagonist reactive nctions followed by the magnification of the obtained structures. The two stars schematize catalyst aggregates with several acidic sites.

Figure 4.22 Schematic drawings of various block copolymers. These long-chain molecules synthetic molecules consist of chemically distinct poiymeric "biocks" (denoted by lines of (Afferent thicknesses in the figure), chemically grafl. (Left to right ) Linear diblock copolymer molecule (AB) linear triblock (ABC) star copolymer brush copolymer. If the blocks are mutually immiscible, under suitable conditions die molecules spontaneously dump together forming an array of mesophases.

In contrast to miktoarm stars, linear triblock terpolymers are comprised of three blocks with different chemical natures arranged in a sequential manner. In this case two junction points exist between blocks within the same chain inducing additional constraints in the arrangement of the blocks in an ordered mesostructme. In analogy to ABC miktoarm stars, the ordered... 

Tapered block A-B-C The A(B) component concentration varies linearly from 100% at one end of the polymeric chain to 0% at the other end ABC-type triblock ... 

For modular synthesis of ABC-type triblock copolymer, two successive CuAAC reactions have to be performed on the central polymer chain (B block). To accomplish this, the B block polymer having both azide and acetylene end groups (heterotelechelic B) has to be used and, moreover, one of the termini has to be protected in order to prevent linear chain extension (cf Scheme P12.2.1) or formation of cyclic products (Scheme P12.4.1). In a straightforward methodology, the terminal acetylene moiety on B is protected and the azide terminus is used to carry out the rst coupling reaction to join the preformed A or C block. Next, the acetylene moiety is to be deprotected to make it available for the second coupling reaction to join the remaining C or A block. 

A block copolymer is a macromolecule that is composed of distinct sections of different chemical species that are chemically bonded together to form a single molecule. The simplest kind is a diblock copolymer, with two blocks, such as poly(styrene>-fe-poly(isoprene), or PS- -PI. A general label for a diblock copolymer is A-fe-B, or simply AB. There are also triblock copolymers that can contain either two or three different species, for example, ABA or ABC, linear multiblocks, for example, ABAB..., and more complicated architectures, such as starblocks or graft copolymers. These are illustrated schematically in Figure 1. 

Figure 21.10 SEC of a linear ABC poly (HEVE-Z7-CEVE-Z7-CDVE) 4 linear triblock copolymer (sample l-2. Table 21.1) and of the corresponding copolymer after cyclization (C-2). P is the fraction of linears that are formed through CDVE coupling, l-2 and d-2 are remaining linears and polycondensates (mainly dimers). (Reprinted with permission from M. Schappacher and A. Deffieux, Atomic force microscopy imaging and dilute solution properties of cyclic and linear polystyrene combs, Journal of the American Chemical Society, 130, 14684-14689, 2008. 2008 American Chemical Society.)...

How is the situation described above modified when the number of blocks increases from two to three Two types of linear triblock copolymers are possible, ABA and ABC. In both cases, there is little effect on the single-chain behavior. However, the many-chain behavior exhibits qualitatively different features. Two effects are most noticeable. ABA triblock copolymers are capable of forming physical networks while ABC triblock copolymers form distinctive mesophases. The two scenarios have no counterpart in the behavior of diblock copolymers or of monomeric shortchain amphiphiles. Since the bulk phase behavior of ABC block copolymers is discussed at length in Chapter 10 we mostly focus on the behavior of ABA triblock copolymers. 

In the case of linear triblock copolymers (also called ttiblock terpolymers) with ABC stmcture, and even more so with higher-order block copolymers (four blocks or higher), the additional complexity allows the formation of many more structures than diblocks. Many of the possible morphologies are displayed in Figure 4. However, understanding this... 

Abstract This review highlights recent (2000-2004) advances and developments regarding the synthesis of block copolymers with both linear [AB diblocks, ABA and ABC triblocks, ABCD tetrablocks, (AB)n multiblocks etc.] and non-linear structures (star-block, graft, miktoarm star, H-shaped, dendrimer-like and cyclic copolymers). Attention is given only to those synthetic methodologies which lead to well-defined and well-characterized macromolecules. 

The study of both star and linear PS-fr-PEO-fr-PCL triblock copolymers demonstrates the complexity of the crystallization behavior of ABC triblock copolymers and also the multiple possibilities of modifying the crystallization behavior of the block components by changing composition and/or molecular architecture. 

S. Kubowicz, J.F. Baussard, J.F. Lutz, A.F. Thunemann, H. von Berlepsch, A. Laschewsky, Multicompartment micelles formed by self-assembly of linear ABC triblock copolymers in aqueous medium, Angew. Chem. Int. Ed. 44 (2005) 5262-5265. 

Fig. 25 Influence of the block sequence on the packing behavior of the linear ABC triblock molecules [172] phase sequences 88 ...

Xia Y, Chen J et al (2010) Self-assembly of linear ABC coil-coil-rod triblock copolymers. Polymer 51 3315-3319... 

Other ABC triblock copolymers were prepared using mono-, di-, and trifunctional initiators to produce ABC, ABCBA, and [ABC]3 linear and 3-arm star block copolymers. For example, a difunctional pSt macroinitiator (Mn=1100, Mw/Mn=1.17) was chain extended with tBA (Mn=l 1,200, Mw/Mn=1.16) which was subsequently chain extended with MA (Mn=27,250, Mw/Mn=l. 14), as shown in Fig. 21. 

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