SANS and SLS Studies on Tetra-Arm PEG Gels in As-Prepared and Swollen States
SANS and SLS Studies on Tetra-Arm PEG Gels in As-Prepared and Swollen States
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DOI：
10.1021/ma901013q
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发表时间：
2009-08-25
期刊：
影响因子：
5.5
通讯作者：
Shibayama, Mitsuhiro
中科院分区：
文献类型：
--
作者：
Matsunaga, Takuro;Sakai, Takamasa;Shibayama, Mitsuhiro
制备了一系列由聚乙二醇（PEG）、四聚乙二醇（tetra-PEG）凝胶组成的模型网络，并用小角中子散射（SANS）和静态光散射（SLS）研究了它们的结构和动力学。Tetra-PEG凝胶是通过两种类型的四臂PEG大分子单体的交叉末端偶联制备的，分子量M-w为（5至40）x 10（3）g/mol。在SANS体系中，制备的和溶胀的凝胶的结构因子都可以由Ornstein-Zernike型散射函数表示，并叠加到具有约化变量xi q和I（q）/phi（0）xi（2）的单个主曲线上，而与四PEG的分子量无关，其中q、xi、I（q）和phi（0）是散射矢量的大小，相关长度，散射强度和制备时的聚合物体积分数。然而，在SLS制度，观察到幂律型上升，表明PEG链簇的存在。有趣的是，这些不均匀性通过膨胀而消失。它的结论是，Tetra-PEG凝胶可以是一个“理想的聚合物网络”与自相似的结构相对于M-W没有显着的缠结和/或缺陷。这解释了为什么Tetra-PEG具有高机械强度，如其他地方所报道的（Macromolecules 2008，41，5379）。
A series of model networks consisting of polyethylene glycol (PEG), tetra-PEG gels, have been prepared and their structure and dynamics have been investigated by small-angle neutron scattering (SANS) and static light scattering (SLS). The Tetra-PEG gels were prepared cross-end coupling of two types of tetra-arm PEG macromers with molecular weights, M-w, of (5 to 40) x 10(3) g/mol. In the SANS regime, the structure factors of both as-prepared and swollen gels can be represented by Ornstein-Zernike-type scattering functions and superimposed to single master curves with the reduced variables, xi q and I(q)/phi(0)xi(2), irrespective of the molecular weight of tetra-PEG, where q, xi, I(q), and phi(0) are the magnitude of the scattering vector, the correlation length, the scattering intensity, and the polymer volume fraction at preparation, respectively. In the SLS regime, however, a power-law-type upturn was observed, indicating the presence of PEG chain clusters. Interestingly, these inhomogeneities disappear by swelling. It is concluded that Tetra-PEG gels can be an "ideal polymer network" with a self-similar structure with respect to M-w without significant entanglements and/or defects. This explains why Tetra-PEG gets have high mechanical strength as reported elsewhere (Macromolecules 2008, 41, 5379).