COLL 547 |
| Dennis E. Discher, Dept. Chemical & Biomolecular Eng'g, Dept. Chemical & Biomolecular Eng'g, University of Pennsylvania, Philadelphia, PA 19104 |
| Giant and stable worm-like micelles formed in water from a suitably-proportioned series of polyethyleneoxide-based (PEO) diblock copolymer amphiphiles are shown to mimic the wide ranging flexibility of natural filaments from linear phages to microtubules. Worm diameter (d) is found, by cryo-TEM, to scale with the length of the hydrophobic chain (N) of the copolymer as N^0.61, which is close to the strong segregation limit scaling. By fluorescence video imaging of worm dynamics, we also show that the persistence length (lp) of worm-like micelles scales as~ d^2.8, consistent with a fluid aggregate (~d^3) rather than a solid rod (~d^4). By polymerizing the unsaturated bonds of assembled copolymers, fluid worms are converted to solid-core worms, extending the bending rigidity to millimeters. Through partial crosslinking, polymerized worms are shown to lock in a spontaneous curvature at a novel fluid-to-solid percolation point. The dynamics of distinct, branched conformations are also imaged for recently discovered Y-junctioned worm-like micelles composed of diblocks of high molecular weight (>10-15 kg/mol). Finally, block copolymers of hydrophilic weight fraction (wEO) close to the transition between a vesicle- and worm-former are shown to assemble into both structures, allowing encapsulation of worm-like micelles in giant vesicles reminiscent of cytoskeletal filaments enclosed within cells. |
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“Smart” Polymers on Surfaces and Colloids
2:00 PM-4:50 PM, Thursday, April 1, 2004 Marriott -- Grand Ballroom J, Oral
Division of Colloid and Surface Chemistry |