Sunday, April 29, 2007

Effects of the molecular weight on the morphology of micron-sized dextran particles prepared using the supercritical anti-solvent process

Seon-Gyun Rho1, Sung-Yong Cho1, Seung-Jai Kim1, Jae-Soon Shin2, and Choon-Hyoung Kang2. (1) Department of Environmental Engineering, BK21 Development of Environmentally friendly core materials and processes, Chonnam National University, 300, YongBongDong, BukGu, Gwangju, 500-757, South Korea, (2) Department of Applied Chemical Engineering, Chonnam National University, 300, YongBongDong, BukGu, Gwangju, 500-757, South Korea

In this work, micron-sized dextran(DEX) particles were prepared by means of the Supercritical Anti-solvent(SAS) process, in which the addition of a supercritical fluid results in a phase-splitting of the organic polymer solution. The operating temperature, pressure, the injection rate of the solution and the solute concentration are some of the important variables that affect on the size and morphology of the resulting particles. Furthermore, it is also natural to focus on the effect of the polymer molecular weight on the polymer particle formation considering the inherent polydispersiy in order to secure an effective way to regulate the resulting particle size and its morphology.
In this effort, several dextrans of different molecular weights and their distributions were used to manufacture micron-sized particles, of which the size ranged 300~400µm. The high temperature and pressure led to large particle size. The concentration of the polymer solution showed a similar consequence except that the particles showed a more extensive aggregation at very low concentration. The higher the molecular weight of dextran, the larger the size of the resulting particle. In addition, the aggregation tendency of the formed particles was pronounced for the higher molecular weight dextran. This can be attributed to the fact that the phase-splitting region for the larger molecular weight polymer system is more enlarged and the nucleation rather than the spinodal decomposition leads to the following process.  

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