Tuning polymer architecture to manipulate the relative stability of different colloid crystal morphologies

The architecture of a polymer adsorbed in a colloidal crystal controls the crystal's thermodynamic stability relative to competing polymorphs.

Preparation of Ordered TiO2 Macroporous Membrane Using PBMA Colloid Crystal as Template

Poly(butyl methacrylate) (PBMA) colloidal crystal templates were assembled orderly on the clean substrates of monocrystalline silicon by dip-drawing technique and titanium dioxide (TiO2) macroporous membranes were prepared by using sol-dipping template method to fill the interstices among the PBMA templates, followed by calcination to remove the templates at 550°C. Calcination of the PBMA templates was carried out according to the following procedure: the rate of rising temperature was 5°C/min from room temperature to 150°C, 2°C/min from 150°C to 270°C, 1°C/min from 270°C to 430°C, 2°C/min from 430°C to 550°C and maintained it at 550°C for 2h. X-ray diffraction (XRD) spectra indicated the macroporous materials were anatase structure. The polymerization mechanism of BMA with Fenton reagent as a new initiator was discussed, and the removal process of the PBMA templates and the formation of TiO2pore size were investigated, respectively. The results showed that the new method of polymerization overcomes many problems associated with the conventional emulsion polymerization techniques such as long reaction time, necessary deoxygenation, and complicated operation.

Flow Induced Crystallization of Colloidal Dispersion

In this study, we have examined a crystallization effect of colloidal dispersion induced by the various elongational flows. Extremely strong electrostatic repulsion makes a crystal structure called ‘colloid crystal’. A colloid crystal has hundreds of nano-meters in grating scale and it reflects the visible light due to the Bragg diffraction. It has the potential to become different photonic devices such as an inexpensive photonic device and a planar laser source, but it requires the evolution of the process of making a single-crystal with external stimulus. The methods using flow operation described in this study are expected to the crystallization action of a colloidal dispersion. In the experiment, 2 types of the flow have been examined. The flows have a contraction or an expansion part between two parallel plates separated by 0.1 mm gap and it cause deformations of a contraction or an extension for the colloid. We have evaluated the crystallization effects by a spectroscopic observation of visible-lights reflection on the flow region. As a result, while expansion flows have no crystallization effect, contraction flows have shown it.