Structural characterization of amphiphilic homopolymer micelles using light scattering, SANS, and cryo-TEM.
We report the aqueous solution self-assembly of a series of poly(N-isopropylacrylamide) (PNIPAM) polymers end-functionalized with a hydrophobic sulfur-carbon-sulfur (SCS) pincer ligand. Although the hydrophobic ligand accounted for <5 wt% of the overall homopolymer mass, the polymers self-assembled into well-defined spherical micelles in aqueous solution, and these micelles are potential precursors to solution-assembled nanoreactors for small molecule catalysis applications. The micelle structural details were investigated using light scattering, cryogenic transmission electron microscopy (cryo-TEM), and small angle neutron scattering (SANS). Radial density profiles extracted from the cryo-TEM micrographs suggested that the PNIPAM chains formed a diffuse corona with a radially decreasing corona density profile and provided valuablea prioriinformation about the micelle structure for SANS data modeling. SANS analysis indicated a similar profile in which the corona surrounded a small hydrophobic core containing the pincer ligand. The similarity between the SANS and cryo-TEM results demonstrated that detailed information about the micelle density profile can be obtained directly from cryo-TEM and highlighted the complementary use of scattering and cryo-TEM in the structural characterization of solution-assemblies, such as the SCS pincer-functionalized homopolymers described here.
University of Warwick, Department of Chemistry, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom.
Joseph P
JP
Patterson
Elizabeth G
EG
Kelley
Ryan P
RP
Murphy
Adam O
AO
Moughton
Mathew
M
Robin
Annhelen
A
Lu
Olivier
O
Colombani
Christophe
C
Chassenieux
David
D
Cheung
Millicent O
MO
Sullivan
Thomas H
TH
Epps
Rachel K
RK
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