Block linear triblock

The dynamic melt viscosity measurements of select star blocks and a similar triblock were carried out on a rheometric mechanical spectrometer, RMS. Circular molded samples of 2 cm diameter and -1.5 mm thickness were subjected to forced sinusoidal oscillations. Dynamic viscosities were recorded in the frequency range of 0.01-100 rad/s at 180 °C. Figure 10 shows the complex viscosities of two select star blocks and a similar linear triblock. The plots showed characteristic behavior of thermoplastic elastomers, i.e., absence of Newtonian behavior even in the low frequency region. The complex viscosity of the star block... 

Poly[(A)-s-(A )-s-(B)] three-arm star-block copolymer Poly[(A)2-s-(B)] three-arm star-block copolymer Poly[(A)2-s-(B)2] four-arm star-block copolymer Poly[(A)-b-(B)-b-(C)] linear triblock copolymer Poly[(A)-s-(B)-s-(C)] three-arm star-block copolymer N,N- Dimethylacetamide Anionic ring-opening polymerization... 

Since soluble multifunctional initiators are more readily available in cationic polymerization than in the anionic counterpart, ABA type linear triblock copolymers have been almost exclusively prepared using difunctional initiation followed by sequential monomer addition. The preparation and properties of ABA type block copolymer thermoplastic elastomers (TPEs), where the middle segment is PIB, have been reviewed recently [47]. 

GPC fractionation and ozonisis of the products, the yield of cyclic polymer was estimated to be ca. 90%. The morphological transition of the cyclic block polymer depends on composition in essentially the same manner as that of the linear triblock copolymers, whereas the domain spacing of polystyrene-block-polyisoprene cyclic block copolymers were all smaller than those of the corresponding SIS linear triblock copolymers, which is attributed to looped chain conformation. 

Kraus et al. (74,75) studied the steady flow and oscillatory flow behavior of linear triblocks of S-B-S and B-S-B and radial block copolymers of the type (B-S-) 3, (S-B-)3, and (S-B-)4. For block copolymers of the same molecular weight and composition, those with end blocks of PS always have higher viscosities. However, when compared with corresponding linear block copolymers, the viscosities of the radial block copolymers are generally lower. 

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... 

Zhu Y, Gido SP et al (2003) Microphase separation of cyclic block copolymers of styrene and butadiene and of their corresponding linear triblock copolymers. Macromolecules 36 148-152... 

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.

Cyclic block copolymers with blocks that microphase separate in bulk are expected to form only loops at both sides of the interface, while their linear triblock analogues are able to form loops and bridges. This significant difference is expected to give very interesting morphological properties to the cyclic copolymers. 

Spherical micelles with a polybutadiene core were formed for a certain range of compositions of the mixed solvent. The equilibrium between micelles and nonas-sociated macromolecules was found to be consistent with a closed association mechanism. In comparison with a linear triblock copolymer, the star-block sample showed a lower aggregation number. 

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