Triblock rod-coil

A novel coil-rod-coil triblock copolymer, where the rod block was polyflu-orene, PF, and the coil blocks poly(2-tetrahydropyranyl methacrylate),... 

If indeed supramolecular dusters are formed spontaneously in bulk films of appropriately designed rod-coil systems, by inclusion of appropriate reactive units it should be possible to convert these into molecular objects by crosslinking, while maintaining the predse size and shape of the cluster. In order to test this hypothesis, rod-coil triblock copolymers, with structures similar to those described previously, but with a few modifications to enable crosslinking, were prepared. Stupp and coworkers replaced the poly(isoprene) block with a poly( butadiene) (PB) block (which contains both 1,2- and 1,4-linked repeat units), which is known to undergo thermal crosslinking at high temperatures [70]. Additionally, the phenolic OH... 

Figure 11. GPC traces of rod—coil triblock molecule (6) and macromolecular object. (Reprinted with permission from ref 60. Copyright 1999 American Association for the Advancement of Science).

The coil—rod—coil triblock molecule (17) based on polypropylene oxide) (PPO) coil segment was observed to show only an isotropic liquid upon melting. In contrast, the addition of greater than 0.10 mol of lithium salt/propylene oxide (PO) unit induces the formation of a liquid crystalline order (Figure 22). 

Figure 29. SFM image of nonspherical micelles formed by rod-coil triblock copolymer 27. (Reprinted with permission from ref 104. Copyright 1998 American Chemical Society).

Fig. 12 Mesophase structures of the ABA coil-rod-coil triblock molecules...

Another coil-rod-coil triblock copolymer 25 with PS as the flexible block and PPE as the rigid segment has been synthesized by Li and Wang. The aggregation behavior of this copolymer was investigated in selective solvents and in solvent/nonsolvent systems. It was clearly demonstrated that the solvent composition greatly affected the polymer s conformation and the aggregate formation. 

Block copolymers comprised of flexible poly(n-butyl acrylate) or PtBA and rigid P3HT segments have been synthesized by ATRP and by oxidative polymerization (31). Two synthetic routes were followed starting from either the flexible coil for the rod-coil diblock copolymers or the rod P3HT segment for the coil-rod-coil triblock copolymers. ... 

For rod-coil diblock and coil-rod-coil triblock copolymers 53 the effects of micellar morphologies on the photophysical properties were studied by optical absorption (UV-Vis) and PL. The experimental results showed that the diblock PF-b-PlVP (53a) maintained spherical micellar aggregates as the MeOH content increased. The triblock 53b was found to readily aggregate in elongated cylinders due to its symmetric structure (Figure 22). The quantum efficiencies were gradually quenched with increasing MeOH content for both copolymers. 

Scheme 99 Synthesis of polyfluorene-polystyrene coil-rod-coil triblock copolymers...

Godt and coworkers [149] reported on the synthesis of poly(p-phenyleneethynylene)-block-polyisoprene and the transformation of such rod-coils into corresponding coil-rod-coil triblock copolymers. Luminescent rod-coil or coil-rod-coil di- or triblock copolymers were synthesized by mono- or difunctional atom transfer radical polymerization from oligo(p-phenyleneethynylene) [150],... 

Fig. 7. Scheme of mushroom-like supermolecule formed ty oligomeric rod-coil triblock copolymers. Adapted from S. I. Stupp, G. N. Tew, and C. M. Whitaker, in Hyperstructured Molecules I Chemistry, Physics and Applications (H. Sasabe, Ed.). Gordon Breach, Amsterdam, 1999. 

Fang, C., Qi, X.-Y, Fan, Q.-L. et aL (2007) A facile route to semiconductor nanocrystal-semiconducting polymer complex using amine-functionalized rod-coil triblock copolymer as multidentate ligand. Nanotechnology, 18,35704. 

Higashihara, T. and Ueda, M. (2009a) Synthesis and characterization of a novel coil-rod-coil triblock copolymers comprised of regioregular poly (3-hexylthiophene) and poly(methyl methacrylate) segments. Reactive Functional Polymers, 69,457—462. 

Rahman, M.S., Samal, S., and Lee, J.-S. (2007) Quantitative in situ coupling of living diblock copolymers for the preparation of amphiphilic coil-rod-coil triblock copolymer poly(2-vinylpyridine)-fo-poly(n-hexyl isocyanate)-fo-poly(2-vinylpyridine). Macromolecules, 40,9279-9283. 

Figure 19.9 Schematic representation on the molecular arrangement of PEO-b-OFbT-b-PEO triblock copolymers with increasing the volume fraction of PEO at room temperature. (Reprinted with permission from L. Bu, Y. Qu, D. Yan et al., Synthesis and characterization of coil—rod—coil triblock copolymers comprising fluorene-based mesogenic monodisperse conjugated rod and poly(ethylene oxide) coil, Macromolecules, 42, 1580-1588, 2009. 2009 American Chemical Society.)...

Xiao, X., Fu, Y.Q., Zhou, J.J. et al. (2007) Reversible thermally responsive and luminescent coil-rod-coil triblock copolymers. Macromolecular Rapid Communications, 28,1003-1009. 

In three mainly synthetic works Godt et al. and Mullen et al. reported on rod-coil systems having poly(para-phenyleneethynylene) or poly(p rfl-phenyl-ene) as the rod part. Miillen et al. [105] showed the synthesis of poly(para-phenyleneethynylene)-block-poly(ethyleneoxide) by condensation of monofunc-tionalized homopolymer blocks. Godt et al. [106] reported on the synthesis of poly(para-phenyleneethynylene)-block-polyisoprene and the transformation of such rod-coils into corresponding coil-rod-coil triblock copolymers. The synthesis of poly(para-phenylene) as the rod part and polystyrene or poly(ethyl-eneoxide) as the coil part by condensation of prepolymers was also reported by Mullen et al. [107],... 

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