Laser-light-scattering study of structure and dynamics of waxy corn amylopectin in dilute aqueous solution
Laser-light-scattering study of structure and dynamics of waxy corn amylopectin in dilute aqueous solution
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DOI：
10.1016/j.carbpol.2005.11.017
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发表时间：
2006-05
影响因子：
11.2
通讯作者：
Cheng Yang;Bo Meng;Mingqing Chen;Xiaoya Liu;Y. Hua;Z. Ni
中科院分区：
文献类型：
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作者：
Cheng Yang;Bo Meng;Mingqing Chen;Xiaoya Liu;Y. Hua;Z. Ni
采用静态光散射法对糯玉米支链淀粉在水溶液中的平均分子量（M¯w）、旋转半径（<Rg>）、二次维里系数（A2）和分形维数（df）进行表征。结果表明，单蜡玉米支链淀粉分子与线状聚合物相比结构致密，呈膨胀的支链团。与之相关的糯玉米支链淀粉分子呈非膨大的分枝团簇状。采用动态光散射法研究了糯玉米支链淀粉在稀水溶液中的动态变化。当qRg≤2（其中q为支链淀粉的散射矢量，Rgis为支链淀粉的旋转半径）时，呈现单线宽分布，这是由糯玉米支链淀粉在稀水溶液中的平动扩散引起的。平均水动力半径<Rh>可由Stokes-Einstein方程求得。当qRg>2时，蜡质玉米支链淀粉的动态以蜡质玉米支链淀粉分支切片的内部运动为主导，第一个累积线宽（<Γ>）可以缩放到散射矢量(q) <Γ> ~ qn（n=2.73±0.06）。动态激光散射发现，在一定的观察长度下，支链淀粉的一些内部运动没有被发现，并且由于支链淀粉的超支化结构，一些内部运动被抑制。随着qRg的增加，其还原累积量Γ*=<Γ>/(q3kBT/η0)不能接近平台值，且由于糯玉米支链淀粉的支链结构和刚性，其还原累积量<Γ>/(q3kBT/η0)远低于线状聚合物。
The average molecular weight (M¯w), gyration radius (<Rg>), second virial coefficient (A2) and fractal dimension (df) of waxy corn amylopectin in aqueous solution were characterized by static light scattering. The results indicated that the single waxy corn amylopectin molecule had a compact structure compared with the linear polymer and was like a swollen branched cluster. The associated waxy corn amylopectin molecule was like a non-swollen branched cluster. The dynamics of waxy corn amylopectin in dilute aqueous solution were investigated by dynamic light scattering. When qRg≤2 (where q is the scattering vector and Rgis the gyration radius of amylopectin), the single line-width distribution was found, which was caused by the translational diffusion of waxy corn amylopectin in dilute aqueous solution. The average hydrodynamic radius <Rh> could be obtained through Stokes-Einstein equation. When qRg>2, the dynamics of waxy corn amylopectin were dominated by the internal motion of waxy corn amylopectin branching sections, and the first cumulant line-width (<Γ>) could be scaled to the scattering vector (q) as <Γ>∼qn(n=2.73±0.06). It was found that some internal motions were not found at certain observation length by dynamic laser light scattering and some internal motions were suppressed due to the hyperbranched structure of amylopectin. The reduced cumulant Γ*=<Γ>/(q3kBT/η0) could not approach a plateau value with increase of the qRg, and the <Γ>/(q3kBT/η0) value of waxy corn amylopectin was much lower than the value of the linear polymer due to the branched structure and rigid chain of waxy corn amylopectin.