Molla Islam - Nano-scale self-assembly impeded by CH···π interaction in block selective solvents in the case of oligostyrene-perylenediimide-oligostyrene (coil-rod-coil) molecule.

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  Publication Details (including relevant citation   information): Islam, Molla Rafiquel, Sundararajan,   Pudupadi R., Eur. Polym. J., 2013,   49 (8), pp 2042-2051

  Abstract: Self-assembly of surfactants and block   copolymers is normally facilitated by block-selective solvents,   i.e., one of the blocks being sol. and the insol. block   self-assembling. In contrast to this phenomenon, we present the   case of oligostyrene-perylenediimide-oligostyrene coil-rod-coil   mol., which does not show self-assembly of the perylene segment   in solvents that are selective for oligostyrene. We attribute the   preclusion of self-assembly to the C-H···π interaction that   develops between the Ph side groups of the oligostyrene segment   and the perylene π system. In the oligostyrene-selective   solvents, the chain would be extended, facilitating such C-H···π   interaction. With the ring current of perylene shielding the   chem. environment of Ph CH in soln., the chem. shift of Ph -CH in   1H NMR showed a small shift from 7.15 (for the amino-PS) to 7.08   ppm. It is known that the C-H···π interaction is very weak. While   such a C-H···π interaction generally promotes self-assembly and   plays a role in host-guest complexes, the opposite effect is seen   in the present case. It was found that collapsing the   oligostyrene chain by the addn. of a non-solvent leads to the   self-assembly of the perylene segment. [on SciFinder(R)]

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