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Heterogeneity, block length

Block length polydispersity indices"for blends were calculated on the assumption that the block polymers, as prepared, were composed of monodisperse blocks. This is, of course, an approximation justified only by the narrowness of the molecular weight distribution in polymerizations of the present type. The block heterogeneity indices given here should, therefore, be regarded as relative measures of breadth of distribution. [Pg.276]

Figure 11. Maximum low temperature loss tangent (35 Hz) measured normal to mold flow vs. styrene block length heterogeneity. Circles— branched polymers, triangles—linear polymers, solid symbols—electron micrographs displayed. Figure 11. Maximum low temperature loss tangent (35 Hz) measured normal to mold flow vs. styrene block length heterogeneity. Circles— branched polymers, triangles—linear polymers, solid symbols—electron micrographs displayed.
Extreme differences in PB block length curiously appear to extend the range in PS block heterogeneity in which polystyrene-continuous morphologies are possible. For example, Figure 13 shows a straight blend of linear SBS polymers in which both kinds of blocks vary tenfold in length (composition F) ... [Pg.288]

SF calculations for adsorption from a selective solvent were carried out by van Lent and Scheutjens [39]. Of course, the calculations had to deal with the self-assembly process as well. For the case of a rather poorly soluble block connected to a soluble block and not too extreme block lengths the critical micellization concentration (CMC) is extremely low. For any practical situation it then can be safely assumed that adsorption takes place from a solution of almost constant chemical potential, so in equilibrium there is no significant effect of concentration. The longer the A blocks (and hence the shorter the B blocks), the thicker the A film and the higher the density of the brush of B blocks. These calculations make clear that it is favorable to use a strongly insoluble block as anchor, and that the wettability of the solvent-substrate pair by A is important. The case of a heterogeneous layer of hemimicelles requires a more elaborate two-dimensional SF scheme, which was not considered by Van Lent. [Pg.140]

Under such chromatographic conditions it is possible to determine the heterogeneities of the polymer chain selectively and without any influence of the polymer chain length. LC-CC has been successfully used for the determination of the functionality type distribution of telechelics and macromonomers [104-109], for the analysis of block copolymers [111-114], macrocyclic polymers [115], and polymer blends [116-118]. [Pg.33]

Synthetic peptide-based polymers are not new materials homopolymers of polypeptides have been available for many decades and have only seen hmited use as structural materials [5,6]. However, new methods in chemical synthesis have made possible the preparation of increasingly complex polypeptide sequences of controlled molecular weight that display properties far superior to ill-defined homopolypeptides [7]. Furthermore, hybrid copolymers, that combine polypeptide and conventional synthetic polymers, have been prepared and combine the functionality and structure of peptides with the processabihty and economy of polymers [8,9]. These polymers are well suited for applications where polymer assembly and functional domains need to be at length scales ranging from nanometers to microns. These block copolymers are homogeneous on a macroscopic scale, but dissimilarity between the block segments typically results in microphase heterogeneity yield-... [Pg.2]

On the other hand, when the polymer liquid is made of heterogeneous chains, a very spectacular signal I(q) is obtained, and this situation is typical. Let us consider, for instance, a liquid made of monodisperse di-block copolymers, whose subchains are isotopic varieties (and therefore chemically identical). Let us assume that these subchains have the same length... [Pg.286]


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See also in sourсe #XX -- [ Pg.289 ]




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Heterogeneity length

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