Two-Step Folding of Donor-Acceptor Foldamers


Autoria(s): Ramkumar, SG; Ramakrishnan, S
Data(s)

01/03/2010

Resumo

In a series of polymers containing alternately placed electron-rich dialkoxyilaphthalene (DAN) donors and electron-deficient pyromellitic diimide (PDI) acceptors linked by hexa(oxyethylene) (OE-6) segments, the ability to form a folded D-A stack was intentionally disrupted by random inclusion of varying amounts of a comonomer that is devoid of DAN donor units. NMR spectroscopic studies of folding in these copolymers, induced by NH4SCN that coordinates with the OE-6 segments and facilitates the charge-transfer (C-T) induced D-A stacking, clearly reveals the presence of PDI units that are isolated and those that are located at the ends of (D-A),, stacks. Similar conclusions regarding the presence of stacked and unstacked regions along the polymer chain were also inferred from UV-vis spectroscopic studies that probe the evolution of charge-transfer band. One fascinating aspect of these copolymers wits their ability to undergo it two-step folding: first, short (D-A),, stacks are formed by the interaction of the NH4+ ion with some specific regions of the polymer chain, and subsequently these Stacks are further stacked via a two-point interaction with it suitably designed external folding agent that carries a DAN unit and all ammonium group. In the second step, the interaction first occurs by the coordination of the ammonium group of the folding agent with the OE-6 segment, which in turn facilitates the C-T interaction of the DAN unit with the adjacent uncomplexed PDI units along the polymer chain, leading to an increase ill the slacking. Variations of several spectral features, during both UV-vis and NMR spectroscopic titrations, clearly reveal this novel two-step folding process.

Formato

application/pdf

Identificador

http://eprints.iisc.ernet.in/26227/1/ma902737b.pdf

Ramkumar, SG and Ramakrishnan, S (2010) Two-Step Folding of Donor-Acceptor Foldamers. In: Macromolecules, 43 (5). pp. 2307-2312.

Publicador

American Chemical Society.

Relação

http://pubs.acs.org/doi/abs/10.1021/ma902737b

http://eprints.iisc.ernet.in/26227/

Palavras-Chave #Inorganic & Physical Chemistry
Tipo

Journal Article

PeerReviewed