Polystyrene-fc-polyisoprene

Polyisoprene-fc-polystyrene-fc-poly(vinyl methyl ether). 148... 

In the search for new materials, the idea of block copolymers emerged. Block copolymers are materials produced by the careful control of the synthesis a polymer and contain regular sequences of more than one type of monomer. In 1965, Shell brought to the market a number of polystyrene-fc/ock-polybuta-diene- /uck-polystyrene and polystyrene-fe/ock-polyisoprene-fc/ock-polystyrene... 

In addition, polymer micelles have been demonstrated to be more stable and also have a significantly lower cmc than surfactant micelles. Further discussion of surfactant micelles is beyond the scope of this review, and, instead, the reader is directed to a recent review article by Armes. In fact, the polymer building blocks need not be amphiphilic and such phase-separated nanostructures can be formed from completely hydrophobic or lipophilic diblock copolymers that contain two segments with differing solubility (such as polystyrene- -polyisoprene) and hence can undergo phase separation in selective solvents. One example of such completely hydrophobic phase-separated micelles are those reported by Wooley and coworkers, which can be obtained from toluene and acetone solutions of a [polystyrene-a/f-poly(maleic anhydride)]-fc-polyisoprene Iriblock. Conversely, inverse structures are also accessible and are known as reverse micelles. These can be formed by adding a nonsolvent for the hydrophilic block to afford the opposite of a conventional micelle, for which the hydrophilic core is surrounded by a hydrophobic shell in a hydrophobic surrounding media. There have been a handful of reports on the application of these reverse micelles, for example, as nanoreactors and for the extraction of water-soluble molecules. ... 

Other studies on the properties of block copolymers with more complicated architectures exist, although not all of them consider tack. Some studies comparing properties of radial versus simple block architecture allow to compare the effect of chemical versus physical crosslinks in the case of structured systems. The data shows that there is a decrease of melt viscosity together with better adhesive properties for star copolymers [44]. This is related to a point that was discussed earlier the different architectures of the molecules lead to different physical crosslinking densities. In the same spirit, block copolymers with four different arms, two polyisoprene, and two polystyrene-fc-poly(ethylene/butylene) arms were studied, and led to a better combination of shear strength and melt viscosity for adhesive applications [45], compared to the conventional linear SIS and SEBS triblocks. 

Fig. 9.6 Radius of gyration (Rq)/(R j (lower curve) and average squared end-to-end distance (upper curve) versus / for a good solvent. ) is the mean-squared radius of gyration for a single polymer chain. The solid circles are data for polystyrene and polyisoprene from Ref 180. The crosses are from the off-lattice MC simulations of Freire et al. for N = 49 or 55. The other symbols are from MD simulations for monomers interaeting with a purely repulsive Lennard-Jones interaction, eq. (9.3), at T=l.2e/ke for A=100(o) and at r=4.0e/fc s for = 2.5(7 for A = 50(A) and 100 ( ). The solid line has slope of 0.41. (From Ref 117.)...

Ogawa T, Sakamoto N, Hashimoto T, Han CD, Baek DM (1996) Effect of volume fraction on the order-disorder transition in low molecular weight polystyrene-fc/ock-polyisoprene copolymers. 2. Order-disorder transition temperature determined by small-angle X-ray scattering. Macromolecules 29 2113-2123... 

Figure 5 shows an electron micrograph of a polystyrene-fc/ock-polyisoprene film. This specimen was also annealed to enhance the structural regularity. In this case the domain morphology consists of polyisoprene cylinders viewed end-on in a polystyrene matrix. Again a grain texture is revealed. 

Currently, ATRP is the most widely used controlled radical polymerization in anion-to-radical transformation methodology. The first such example was reported by Acar and Matyjaszewski [61], and utilized for the preparation of AB- and ABA-type block copolymers. The macroinitiators, PSt and polyisoprene-b-polystyrene (PIP-fc-PSt) containing 2-bromoisobutyryl end groups were prepared by living anionic polymerization and a suitable termination agent. These polymers were then used as macroinitiators for ATRP to prepare block copolymers with methyl acrylate (PSt-b-PMA), butyl acrylate (PSt-b-PBA), methyl... 

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