Self-assembly of doublets from flattened polymer colloids.

Bottom-up fabrication methods are used to assemble strong yet flexible colloidal doublets. Part of a spherical particle is flattened, increasing the effective interaction area with another particle having a flat region. In the presence of a moderate ionic strength, the flat region on one particle will preferentially "bond" to a flat region on another particle in a deep (≥10 kT) secondary energy minimum. No external field is applied during the assembly process. Under the right conditions, the flat-flat bonding strength is ≥10× that of a sphere-sphere interaction. Not only can flat-flat bonds be quite strong, but they are expected to remain freely rotatable and flexible, with negligible energy barriers for rotation because particles reside in a deep secondary energy minimum with a ~20-30 nm layer of fluid between the ~1 μm radius particles. We present a controlled technique to flatten the particles at room temperature, the modeling of the interparticle forces for flattened spheres, and the experimental data for the self-assembly of flat-flat doublets.

[1]  D. A. Saville,et al.  Colloidal Dispersions: ACKNOWLEDGEMENTS , 1989 .

[2]  H. Brenner.  The slow motion of a sphere through a viscous fluid towards a plane surface , 1961 .

[3]  C. V. van Kats,et al.  Synthesis of colloidal silica dumbbells. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[4]  H. Möhwald,et al.  Patterning microsphere surfaces by templating colloidal crystals. , 2005, Nano letters.

[5]  B. Derjaguin,et al.  Theory of the stability of strongly charged lyophobic sols and of the adhesion of strongly charged particles in solutions of electrolytes , 1993 .

[6]  P. Schultz,et al.  Cover Picture: Expanding the Genetic Code (Angew. Chem. Int. Ed. 1/2005) , 2005 .

[7]  S. Pickup,et al.  Self-diffusion of toluene in polystyrene solutions , 1989 .

[8]  J. L. Duda,et al.  Diffusion in polymer—solvent systems. I. Reexamination of the free‐volume theory , 1977 .

[9]  Darrell Velegol,et al.  Controlled flats on spherical polymer colloids. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[10]  John C. Berg,et al.  Evidence of a hairy layer at the surface of polystyrene latex particles , 1995 .

[11]  Darrell Velegol,et al.  Simple fabrication of metallic colloidal doublets having electrical connectivity. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[12]  D. Prieve,et al.  Prediction and measurement of the optical trapping forces on a microscopic dielectric sphere , 1992 .

[13]  Michael A. Bevan,et al.  DIRECT MEASUREMENT OF RETARDED VAN DER WAALS ATTRACTION , 1999 .

[14]  W. Russel,et al.  Simplified predictions of hamaker constants from Lifshitz theory , 1988 .

[15]  G. Whitesides,et al.  Asymmetric dimers can be formed by dewetting half-shells of gold deposited on the surfaces of spherical oxide colloids. , 2003, Journal of the American Chemical Society.

[16]  S. Sacanna,et al.  Lock and key colloids , 2009, Nature.

[17]  E. Furst,et al.  Fabrication of unusual asymmetric colloids at an oil-water interface. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[18]  Darrell Velegol,et al.  Nanoscale functionalization and site-specific assembly of colloids by particle lithography. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[19]  P. J. Bray,et al.  The effect of molecular structure on borosilicate glass leaching , 1986 .

[20]  E. M. Lifshitz,et al.  The general theory of van der Waals forces , 1961 .

[21]  Ho Cheung Shum,et al.  Controlled buckling and crumpling of nanoparticle-coated droplets. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[22]  D. Velegol,et al.  Maskless fabrication of nanowells using chemically reactive colloids. , 2011, Nano letters.

[23]  Darrell Velegol,et al.  Fabrication of colloidal doublets by a salting out-quenching-fusing technique. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[24]  I. Kretzschmar,et al.  Patchy particles by glancing angle deposition. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[25]  J. L. Duda,et al.  A free‐volume interpretation of the influence of the glass transition on diffusion in amorphous polymers , 1978 .

[26]  Philippe Barboux,et al.  Leaching of borosilicate glasses. I. Experiments , 2004 .

[27]  J. Esteve,et al.  TMAH/IPA anisotropic etching characteristics , 1993 .

[28]  H. Ohshima,et al.  Improvement on the Hogg—Healy—Fuerstenau formulas for the interaction of dissimilar double layers: I. Second and third approximations for moderate potentials , 1982 .

[29]  Mojtaba Kahrizi,et al.  On hillocks generated during anisotropic etching of Si in TMAH , 1996 .

[30]  G. Whitesides,et al.  Direct measurement of interfacial interactions between semispherical lenses and flat sheets of poly(dimethylsiloxane) and their chemical derivatives , 1991 .

[31]  S. Glotzer,et al.  Anisotropy of building blocks and their assembly into complex structures. , 2007, Nature materials.

[32]  D. Prieve,et al.  Hindered diffusion of colloidal particles very near to a wall: Revisited , 2000 .