Multiblock, linear

Figure 6.6 Chemical pathway of the synthesis of multiblock linear and cross-linked SM PU by incorporating high MW PCL soft segment as switch phase (a) and demonstration of the shape memory effect setting r,j3 5 = 80°C (b). Abbreviations - MDI methylene diphenyl diisocyanate, Pluronic ...

Kakimoto and coworkers [163] prepared multiblock linear-hb copolymers by a two-step method involving polymerization of the AB monomer, namely [4-(phenoxy)benzenesulfonyl chloride], to generate the linear block followed by addition of the AB2 monomer 4,4 -(m-phenylene-dioxy)-bis(benzenesulfonyl chloride) in large molar excess (AB2 AB = 19 1) to generate the hb block. The monomer combinations of linear block AB and AB2 are shown in Table 4, entry 5. The thermal properties of multiblock linear-hb polymers were compared with the homo-linear and homo-hb polymers. 

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 effects of architecture and block mass on the morphology and properties of linear multiblock copolymers was investigated by Spontak et al. [43]. They compared two matched series of compositionally symmetric (PS-fc-PI) block copolymers with 1 < n < 4, one possessing a constant chain mass and the other one having a nearly constant block mass. 

The actual knowledge of the basic molecular structure property relationships relies mainly on the availability of well defined linear architectures the di, tri- and multiblock copolymers. New and well controlled molecular structures could undoubtedly provide a deep understanding of the behavior of block copolymers and a more efficient mastering of their applications. ... 

There have only been a very limited number of studies on multiblock copolymers with controlled block length (we exclude here the vast literature on random block copolymers such as polyurethanes). Microphase separation in (PS-PI) linear multiblocks with 1 < n < 4 with nearly equal block lengths was studied by Spontak and co-workers (Smith et al. 1993,1994). All (symmetric) samples were... 

Fig. 8 Synthesis of monocyclic (one disulfide linkage) and linear multiblock polymers through thiol-thiol coupling reactions...

Spontak RJ, Smith SD (2001) Perfectly-alternating linear (AB)n multiblock copolymers effect of molecular design on morphology and properties. J Polym Sci B 39 947-955... 

Wu L, Cochan EW et al (2004) Consequences of block number on the order — disorder transition and viscoelastic properties of linear (AB)n multiblock copolymers. Macromolecules 37 3360-3368... 

The same group has also presented Monte Carlo calculations on the compati-bilizing effect of comb copolymers [328]. Their interfacial behavior was compared with that of linear multiblock copolymers. By varying the numbers and lengths of the teeth it was demonstrated that combs with fewer and longer teeth localize themselves easier at the interface between two homopolymers, of the same nature as the backbone and teeth, than combs with a larger number of shorter teeth. In... 

There are many notations for representing block polymers. We have followed the most common in using A to represent a block of A mer units, with similar representation for B, C, etc., as shown in Table I. Here A-B represents a two block polymer, A-B-C a three block polymer, and A-B-A represents a three block polymer with A terminal blocks and B center blocks. (A-B)jj represents a linear multiblock polymer of alternating A and B blocks. 

During the last decade, more and more advanced techniques of living or controlled polymerization to prepare block copolymers have become available. It has become possible to prepare block copolymers of various architectures, solubility, and functionality [6]. Architectures comprise diblock, triblock, and multiblock copolymers arranged linearly, as stars or grafts. The solubilities vary from polar solvents such as water to media with very low cohesion energies such as silicon oil or fluorinated solvents. Control of functionality has become impor-... 

Block copolymers, BC, are macromolecular species in which long chains of one polymer are joined to long chains of another polymer. Thus, BC s are made of at least two chemically different chains arranged linearly, in form of multi-branch stars, combs, etc. Linear block copolymers are the most common — diblock, AB, triblock, ABA, or multiblock, A(BA). ... 

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