Polyisoprene blocks

B = B 4, 1,4-polybutadiene block Bj 2, 1,2-polybutadiene block B y, medium vinyl (35-60%) polybutadiene block) I, 1,4-polyisoprene block. Selective hydrogenation this block not hydrogenated. 

The block copolymers shown in both Table V and VI were hydrogenated. The B-lU block produced polyethylene and the polyisoprene block produced ethylene propylene alternating copolymer. The physical properties of this copolymer, composed of crystalline polyethylene block and a soft elastomeric segment made of an EPR block, is tabulated in Table VII. The data in this table illustrate the fact that a diblock of hydrogenated polybutadi ene-polyisoprene gave excellent physical properties. This is a further illustration of the new concept of soft chain interpenetrating the crystalli zable polyethylene chain via chain folding. 

Figure 6.1 Cylindrical micelles of a poly(ferrocenyldimethylsilane)/poly(dimethylsiloxane) or polyisoprene block copolymer showing the central core of the ferrocenylsilane units and the corona of the organic polymer blocks. Reproduced by permission of Prof. I. Manners.

For SI copolymers, the total thickness (d = dA + dB) of the lamellar structure increases with the total molecular weight of the copolymer (Fig. 25). Furthermore, the study of a set of copolymers with a constant molecular weight of the polystyrene block (23000) and a variable molecular weight for the polyisoprene block (from 8000 to 28000) has shown that the thickness dB of the polyisoprene layer increases with the molecular weight of the polyisoprene block MB (Fig. 26), while the thickness dA of the polystyrene layer is independent of the molecular weight of polyisoprene (Fig. 27). The study of a set of copolymers with the same polyisoprene block (17500) but a variable polystyrene one has shown that the thickness dA of the... 

Fig. 26. Influence of the molecular weight Mg of the polyisoprene block on the thickness dg of the polyisoprene layer.

In an investigation of the effect of chain geometry on the two phase morphology of polystyrene-polyisoprene block copolymers, Price et al. have studied films of AB linear, AB stars with 2,3 or 4 branches196,197), graft copolymers 198 200>, and ABC block terpolymers201. ... 

ABC copolymers polystyrene-polyisoprene-poly(vinyl-2-pyridine)(S.I.V2P) with number-molecular average weight of 23000,102000, and 23000 were prepared by stepwise anionic polymerization. Films obtained by solvent casting from methylcyclohexane and benzene were observed by electron microscopy after staining the polyisoprene block with osmium tetroxide or the poly(vinyl-2-pyridine)... 

Rossi has synthetized block copolymers polyisoprene-poly(vinyl-2-pyridine) and polyisoprene-poly(vinyl-4-pyridine) of various composition and molecular weight by anionic polymerization under high vacuum205, 208. The polymerization in THF dilute solutions with Cumylpotassium as initiator yielded a 1,2 + 3,4-microstructure of the polyisoprene block. The polymerization in toluene solutions with sec-butyl-lithium as initiator yielded a 1,4-c/s-microstructure of the polyisoprene block. 

Three diblock copolymers of cis-1,4 polyisoprene (IR) and 1,4-polybutadiene (BR) have been studied in dynamic mechanical experiments, transmission electron microscopy, and thermomechanical analysis. The block copolymers had molar ratios of 1/2, 1/1, and 2/1 for the isoprene and butadiene blocks. Homopolymers of polybutadiene and polyisoprene with various diene microstructures also were examined using similar experimental methods. Results indicate that in all three copolymers, the polybutadiene and polyisoprene blocks are essentially compatible whereas blends of homopolymers of similar molecular weights and microstructures were incompatible. 

Thus a statistical copolymer of ethylene and propyiene is named poly(ethylene-stef-propylene), and an ABA tri-block copolymer of styrene (A) and isoprene (B) is named polystyrene-block-polyisoprene-block-polystyrene. In certain cases, additional square brackets are required. For example, an alternating, copolymer of styrene and maleic anhydride is named poly[styrene-d/f-(maleic anhydride)]. 

Dingv JF, Liu GJ et al (1997) Multiple morphologies of polyisoprene-block-poly (2-cinnamoylethyl methacrylate) and polystyrene-block-poly(2-cinnamoylethyl methacrylate) micelles in organic solvents. Polymer 38 5497-5501... 

Mesophases prepared by dissolution of the copolymer in a preferential solvent for the poly(vinylpyridine) block (acrylic acid, nitromethane, dfoxane, octanol, methylethyl ketone, ethyl acetate, vinyl acetate, styrene and methyl methaaylate) and dry copolymers obtained by slow evaporation of the solvent from the mesophases have been studied by low-angle X-r diffraction electron microscopy Copolymers of isoprene and vinylpyridine exhibit cylindrical hexagonal or lamellar structures dependii upon their comi siton.The influence of the nature, concentration, and polymerization of the solvent, molecular weight and composition of the copolymer, microstructure of the polyisoprene block, and position of the nitrogen atom in the vinylpyridine block on the values of the geometrical parameters of the periodic structures have been establidied ... 

A new star—block copolymer architecture, the inverse star—block copolymer, was recently reported.87 These polymers are stars having four polystyrene-/risoprene) copolymers as arms. Two of these arms are connected to the star center by the polystyrene block, whereas the other two are connected through the polyisoprene block. The synthetic procedure is given in Scheme 32. The living diblocks (I) were prepared by anionic polymerization and sequential addition of monomers. A small quantity of THF was used to accelerate the initiation of the polymerization of styrene. The living diblock copolymer (I) was slowly added to a solution of SiCL. The reaction was monitored by SEC on samples with-... 

The molecular weight of the polyisoprene block in the final triblock copolymer is double that of the polyisoprene block in the di-block living copolymer prior to coupling. Hence,... 

Ren, J., SUva, A. S., and Krishnamoorti, R., Linear viscoelasticity of disordered polystyrene-polyisoprene block copolymer based layered-silicate nanocomposites. Macromolecules, 33, 3739-3746 (2000). 

A typical triblock copolymer may consist of about 150 styrene units at each end of the macromolecule and some 1,000 butadiene units in the center. The special physical properties of these block copolymers are due to inherent incompatibility of polystyrene with polybutadiene or polyisoprene blocks. Within the bulk material, there are separations and aggregations of the domains. The polystyrene domains are dispersed in continuous matrixes of the polydienes that are the major components. At ambient temperature, below the Tg of the polystyrene, these domains are rigid and immobilize the ends of the polydiene segments. In effect they serve both as filler particles and as cross-links. Above Tg of polystyrene, however, the domains are easily disrupted and the material can be processed as a thermoplastic polymer. The separation into domains is illustrated in Fig. 6.4. 

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