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Formation Mechanism of Silica/Diblock Mesophases by Solvent Evaporation-Induced Self-Assembly

Published online by Cambridge University Press:  21 March 2011

Kui Yu ,
Celeste A. Drewien ,
Alan J. Hurd ,
C. Jeffrey Brinker  and
Adi Eisenberg
Kui Yu
Affiliation:
Sandia National Laboratories, MS 1349, Albuquerque, NM
Celeste A. Drewien
Affiliation:
Sandia National Laboratories, MS 1349, Albuquerque, NM
Alan J. Hurd
Affiliation:
Sandia National Laboratories, MS 1349, Albuquerque, NM
C. Jeffrey Brinker
Affiliation:
Sandia National Laboratories, MS 1349, Albuquerque, NM
Adi Eisenberg
Affiliation:
McGill Univ., Dept. of Chem., Montreal, Canada
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Abstract

Intermediate structures were trapped during the mesophase transition from lamellae to higher curvature structures in a sol-gel matrix. The target structures included normal hexagonally arranged cylinders and/or normal spheres in a cubic array distributed in a hydrophilic matrix. The present system is believed to be the first to trap these intermediates. Through solvent evaporation-induced self-assembly (EISA), mesostructured silica/diblock films with large characteristic length scales were prepared. The structure-directing agents were polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers with high molecular weight, which are water insoluble and alcohol insoluble. We believe that no micellization took place in the present system; a disorder-to-order transition occurred due to the cooperative self- assembly of the diblock and silicates as the solvent preferentially evaporated from a film cast from a dilute homogeneous solution. During further preferential evaporation, the morphogenic effect of the increase of species concentration facilitates the mesophase development in the direction of a normal cubic to hexagonal to lamellar pathway. However, the morphogenic effects of both the decrease of the PS coil dimension and the siloxane condensation drive the mesophase development in opposite directions. The decrease of the PS coil dimension plays an important role in the present self-assembly process. Trapping of the intermediates and coexisting multiple mesophases are related to the facts that PS has high Tg and high hydrophobicity in particular, as well as to the fact that polymers have relatively low mobility in general.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 672: Symposium O – Mechanisms of Surface and Microstructure Evolution in Deposited Films and Film Structures , 2001 , O85.1
Copyright
Copyright © Materials Research Society 2001

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References

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