Q&A The Column www.thecolumn.eu.com February 2008 The Winning Hand Alasdair Matheson talks to Desty Memorial Award winner, Haifei Zhang from Liverpool University, about his innovative approach to manufacturing chromatographic supports with novel physical characteristics. Congratulations on winning the 12th Desty Memorial Award for your work on the manufacture of porous materials. What is innovative about this research? Thanks. The target of our research is to prepare hierarchically porous materials and aligned porous materials. This involves combining emulsion templating, polymer templating and the sol-gel process to make materials with hierarchical pores, that is, materials with pore sizes of different lengths. Our main innovation is in the actual preparation of aligned porous materials using a method called directional freezing. SEM images of aligned porous materials are shown in Figure 1. The method is versatile and can be applied to solutions and suspensions for aqueous, organic and even compressed CO2 systems. The preparation process is very simple. A temperature gradient is applied to a solution. The ice crystals grow along one direction while the solution/suspension is being frozen. The frozen solvent is then removed by freeze drying, which generates the aligned porous structures. processes. As a material scientist, my research is focused on preparing novel porous structures with different (ideally controlled) surface functionalities. Porous materials of this type could potentially improve the separation efficiency to a large degree and be applied to large analytes such as protein molecules. As you know from the van Deemter equation the plate height is governed by three factors: the interparticle spacing and pathways; diffusion (axial and longitudinal); and mass transfer kinetics between stationary and mobile phases. We are looking at making particles with a very tight particle size distribution in the hope of reducing the A term and at the same time tune and control surface chemistry and pore morphology to change the C term. Traditional silica-based packings have many problems mainly because they are not sufficiently stable at extreme pH or elevated temperatures. Although the new sub-2 micron particles are known to Why is this research important to separation scientists? The tuning and control of porous structures is critical to separation Figure 1: SEM images of aligned porous materials. Poly(vinyl alcohol) Poly(vinyl alcohol)/silica Polycaprolactone 12 Author: Haifei Zhang E-mail: zhanghf@liverpool.ac.uk
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Table of Contents for the Digital Edition of The Column - February 2008