STRUCTURAL INHOMOGENEITIES IN THE RANGE 2.5-2500 A IN POLYACRYLAMIDE GELS
STRUCTURAL INHOMOGENEITIES IN THE RANGE 2.5-2500 A IN POLYACRYLAMIDE GELS
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DOI：
10.1021/ma00153a018
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发表时间：
1985-01-01
期刊：
影响因子：
5.5
通讯作者：
GEISSLER, E
中科院分区：
文献类型：
--
作者：
HECHT, AM;DUPLESSIX, R;GEISSLER, E
采用光散射（SLS）、小角中子散射（SANS）和小角x射线散射（SAXS）测量了聚丙烯酰胺-共双丙烯酰胺共聚物凝胶的散射函数S (Q)。凝胶的丙烯酰胺含量固定（0.08 g/mL），双丙烯酰胺含量在0 ~ 0.005 g/mL之间变化。发现三组数据可以拼接在一起形成一个单一的连续散射函数S (Q)，其中散射波矢量Q在4 × 104< Q< 1.5 × 107 cm-1范围内。对比变化的SANS数据表明，光谱可以分为两部分。第一种，均相溶液，产生一个准洛伦兹信号，其相关长度随着双丙烯酰胺含量的增加而增加。高Q值时S (Q)的行为表明，随着双丙烯酰胺的增加，该相聚合物链的横截面半径r0的值从2.5左右增加到4 Á。然而，发现这一阶段的总聚合物含量几乎是恒定的。除了这种均匀光谱外，凝胶中的非均匀成分还会产生过量的正向散射，其特征是浓度波动幅度很大。由于S (Q)与光散射曲线的连续性，可以对S (Q)进行校准，从而可以得到不变量M2tot=/óS (Q) Q2 dQ的贡献，这是由非均质性引起的。此外，在光谱的SANS区域，曲线遵循分形行为，其维数可以随意变化-通过适当选择双丙烯酰胺含量-在0和3之间。
Measurements are presented of the scattering function S (Q) from poly (acrylamide-co-bisacrylamide) copolymer gels using light (SLS), small-angle neutron (SANS), and small-angle X-ray (SAXS) scattering. The gels had a fixed acrylamide content (0.08 g/mL) and a bisacrylamide content that varied between 0 and 0.005 g/mL. It is found that all three sets of data can be spliced together to form a single continuous scattering function S (Q), where the scattering wave vector Q lies in therange 4 X 104< Q< 1.5 x 107 cm-1. Contrast variation SANS data show that the spectra can be separated into two parts. The first, a homogeneous solution, gives rise to a quasi-Lorentzian signal with a correlation length that increases with increasing bisacrylamide content. The behavior of S (Q) at high Q values shows that the value of the radius of cross section r0 of the polymer chains in this phase increases from about 2.5 to 4 Á with increasing bisacrylamide. Thetotal polymercontent in this phaseis found, however, to be approximately constant. In addition to this homogeneous spectrum, there is also excess forward scattering arising from an inhomogeneous component in the gel, which is characterized by concentration fluctuationsof large amplitude. Because of the continuity of S (Q) with the light scattering curves, S (Q) can be calibrated, and one can hence obtain the contribution to the invariant M2tot=/óS (Q) Q2 dQ, which is caused by the heterogeneities. Furthermore, in the SANS region of the spectra, the curves follow a fractal behavior, the dimensionality of which is variable at will—by suitablechoice of the bisacrylamide content—between 0 and 3.