모세관을 이용한 콜로이드 자가조합체의 제조
문준혁, 이기라, 양승만
한국과학기술원 화학공학과
Preparation of macrocrystalline assemblies using an capillary tube
Jun Hyuk Moon, Gi-Ra Yi, Seung-Man Yang
Department of Chemical Engineering
Korea Advanced Institute of Science and Technology, Taejon 305-701
Introduction
Colloidal particles are interesting and versatile building block for twoand three-dimensional microstructures [1]. Well-controlled colloidal
assemblies display a number of potentially applicable characteristics such
as a photonic bandgap [2], high packing density, and high surface-tovolume ratio. For practical applications of these structures, they should
be mounted or shaped into usable objects [3]. To address this problem,
a number of methods have been exploited using colloidal crystallization in
confined geometry, including gravity sedimentation on flat or periodically
patterned substrates, flow of the colloids through micromachined
channels or a smooth narrow pore membrane, and making use of
capillary forces. One of approaches involves the use of a suspension
droplet as a confined geometry. The crystallization of submicrometersized colloidal particles occurs inside the droplet, leading to a highly
ordered colloidal assembly [4] In this work, we prepare the colloidal
crystals using capillary as a confined geometry. Some report a
mesoporous silica fiber with large pores using block copolymers [5]. This
well-ordered colloidal rod or its replica has a potential as optical waveguides, macroporous membranes and catalytic supports.
Experimental
Non-crosslinked, monodisperse PS latex particles were synthesized by
emulsifier-free emulsion polymerization, and micron-size PS latex
particles were prepared by single stage polymerization process using a
surfactant [6] and purchased from Polyscience. We used the capillary
with various different diameters. Macrocrystalline colloidal rods were
produced by PS latex particles and the capillary as templates. The
solution contained with the PS particles put into the capillary through
syringe pump. Colloidal assembly rod in the capillary was separated via
HF treatments.
The colloidal crystal rods were infused with in a metal alkoxide
precursor solution such as titanium(IV) tetraisopropoxide (TTIP) and
tetramethlorthosiilicate (TMOS). This process was conducted under
moisture-free condition because of its high reactivity to water. Composite
rods of crystalline PS latex particles and ceramic matrix were synthesized
through sol-gel reaction. Finally, the rods constituting the composite
colloidal crystals were removed by calcinations.
Results
Figure 1 shows the various colloidal rods. The drying condition
determines the arrangement of colloidal assemblies, and the rod can’t be
separated from the capillary at high drying rate. It is treated by HF
solution, resulting in dissolving the capillary that is made of silica, and we
can obtain the colloidal assembly rod. The capillary has an anion charge
when it is exposed with an aqueous media, and an ionic surfactant,
sodium dodecyl sulphate(SDS) is added to make the colloidal system
stable by changing the surface properties of the particles and the
capillary wall. The sodium ions gather around the capillary wall that
possesses negative surface charges, and eventually change the strength
of the zeta potential on the surface.
The prepared crystalline rods were soaked into a solution of metal
alkoxide precursor, which went through the interstices between the PS
latex spheres by capillary force. The rod used as a template, resulting in
the macroporous rod. The size of the air boids ranged from 100nm-1um,
which depends on the size of PS particles (Figure 2).
Conclusion
We prepared the colloidal crystalline rod with PS latex suspension into
the micron-sized capillary. The size and the length of the rod was obtaind,
depending on the particle and capillary size. We also prepared the
macroporous rods using the colloidal crystalline rod as a template. It has
a potential as optical wave-guides, macroporous membranes and
catalytic supports.
Reference
[1] Y. Xia, G. Bates, Y. Yin, Y. Lu, Adv. Mater, 2000, 12, 693
[2] B. Bates, S. H. Park, Y. Xia, Adv Mater. 2000, 12, 653
[3] van Blaaderan, R. Ruel, P. Wiltzius, Nature 1997, 385, 3210
[4] G.-R. Yi, J. H. Moon, S.-M. Yang, Adv. Mater. 2001, 13, 1185
[5] P. Yang, D. Zhao, B. F. Chmelka, G. D. Stucky, Chem. Mater. 1998,
10, 2033
[6] S. Gu, M. Konno, J. Chem. Eng. Japan 1997, 30, 742
Figure 1. Colloidal crystalline rods
Figure 2. Cross section images of Macroporous rods