Formation and structure of pachyman aggregates in dimethyl sulfoxide containing water

✍ Scribed by Qiong Ding; Lina Zhang; Chi Wu

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 160 KB
• Volume: 37
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(19991115)37:22<3201::aid-polb4>3.0.co;2-5

✦ Synopsis

The aggregation of pachyman, ␤-(1 3 3)-D-glucan (M w ϭ 1.68 ϫ 10 5 ) from the Poria cocos mycelia, was investigated using static and dynamic laser light scattering (LLS) in dimethyl sulfoxide (DMSO) containing about 15% water, which leads to large aggregates. Both the time dependence of hydrodynamic radius and the angle dependence of the scattering intensity were used to calculate the fractal dimension (d f ) of the aggregates. The aggregation rate and average size of aggregates increase dramatically with increasing the polymer concentration from 1.7 ϫ 10 Ϫ4 g/mL to 8.6 ϫ 10 Ϫ4 g/mL, and with the decrease of the solvent quality, that is, water content from 13 to 15%. In the cases, the fractal dimensions change from 1.94 to 2.43 and from 1.92 to 2.54, respectively, suggesting that transforms of aggregation processes: a slow process called reaction-limited cluster aggregation (RLCA) to a fast process called diffusion-limited cluster aggregation (DLCA) in different polymer concentrations and water content. The fractal dimensions above 2 of the fast aggregation is larger than the 1.75 predicted for the ideal DLCA model, suggesting that the aggregation involves a restructuring process through the interchain hydrogen bonding interaction. There are no aggregates of pachyman in DMSO without water, but aggregates formed in the DMSO containing 15% water at 25°C as a compact structure.