Dendrimer-based transient supramolecular networks.
J Am Chem Soc
; 127(40): 13862-8, 2005 Oct 12.
Article
in En
| MEDLINE
| ID: mdl-16201807
ABSTRACT
Association of a 16-fold excess of a monodisperse telechelic oligo(THF) (Mw = 1270 g/mol) containing two end groups that selectively bind to the 32 binding sites of a fifth generation dendritic host (Mw = 18,511 g/mol and radius R(h) = 2.4 nm) results in the formation of reversible and dynamic supramolecular complexes. The structure of these complexes in solution depends strongly on the concentration. At low concentration, the two end groups of one guest are proposed to complex to the same host, and flowerlike structures are formed with a radius of R(h) = 3.7 nm. At higher concentrations, both end groups of one guest are complexed to different hosts, forming a bridge between them. This gives rise to the formation of larger associates, and eventually to a transient supramolecular network. Dynamic light scattering unequivocally showed that three distinct relaxation processes, associated with the proposed structures, are present in this system. In addition to the dynamics related to the flowerlike (fast) and the transient network structures (slow), an intermediate dynamic process is attributed to the cooperative motion of a few (approximately 6) connected flowerlike structures. Rheological data elucidate the nature of the intermittent network responsible for the slowest process. A monofunctional guest, not capable of forming a network structure, was used as a reference, and starlike supramolecular structures are formed at all concentrations, indeed.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Polypropylenes
/
Macromolecular Substances
/
Dendrimers
/
Acetates
Language:
En
Journal:
J Am Chem Soc
Year:
2005
Document type:
Article
Affiliation country:
Países Bajos