Orientational ordering in the nematic phase of a polyethylene glycol-peptide conjugate in aqueous solution.
Orientational ordering in the nematic phase of a polyethylene glycol-peptide conjugate in aqueous solution.
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水溶液中聚乙二醇-肽缀合物的向列相的方向排序。
DOI：
10.1103/physreve.77.062901
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
L. Noirez
中科院分区：
文献类型：
--
作者：
I. Hamley;Marta J. Krysmann;G. Newby;V. Castelletto;L. Noirez
采用小角中子散射（SANS）技术研究了聚乙二醇(PEG)-肽嵌段共聚物在水溶液中向列相的取向顺序，并将样品置于Couette细胞中进行稳定剪切。聚乙二醇-肽缀合物形成的原纤维表现为半柔性的棒状链。采用均匀圆柱形状因子的级数展开方法对数据进行建模，得到了方向序参数P2和P4。所使用的方法不依赖于对单重态方向分布函数形式的假设。得到了与各向异性二维SANS图形较好的一致性。结果表明，剪切排列始于非常低的剪切速率，取向序参数在较高的剪切速率下达到平台，并与剪切速率呈伪对数依赖关系。最可能的分布函数对应于剪切下平行于流动方向的原纤维，但静止样品显示双峰分布，一些棒状肽原纤维垂直于流动方向。
The orientational ordering of the nematic phase of a polyethylene glycol (PEG)-peptide block copolymer in aqueous solution is probed by small-angle neutron scattering (SANS), with the sample subjected to steady shear in a Couette cell. The PEG-peptide conjugate forms fibrils that behave as semiflexible rodlike chains. The orientational order parameters P2 and P4 are obtained by modeling the data using a series expansion approach to the form factor of uniform cylinders. The method used is independent of assumptions on the form of the singlet orientational distribution function. Good agreement with the anisotropic two-dimensional SANS patterns is obtained. The results show shear alignment starting at very low shear rates, and the orientational order parameters reach a plateau at higher shear rates with a pseudologarithmic dependence on shear rate. The most probable distribution functions correspond to fibrils parallel to the flow direction under shear, but a sample at rest shows a bimodal distribution with some of the rodlike peptide fibrils oriented perpendicular to the flow direction.