ON THE SCATTERING PROPERTIES OF POLYELECTROLYTE GELS
ON THE SCATTERING PROPERTIES OF POLYELECTROLYTE GELS
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DOI：
10.1051/jp2:1992219
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发表时间：
1992-08-01
期刊：
影响因子：
--
通讯作者：
PINCUS, P
中科院分区：
文献类型：
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作者：
BARRAT, JL;JOANNY, JF;PINCUS, P
我们提出了一个简单的模型，在溶胀平衡的散射特性的双凝胶。在弱屏蔽限制的Debye-Huckel屏蔽长度大于网格尺寸的凝胶，直接的静电相互作用是可以忽略不计的，溶胀是由反离子的渗透压驱动的。由该压力产生的张力通过交联传递到弹性链，弹性链表现为在其端点处施加力的孤立链。凝胶的结构因子可以分为由于平均浓度不均匀性而产生的冷冻成分和由于浓度波动而产生的热力学成分。冷冻组分在凝胶的筛目尺寸的量级的波矢量处具有峰，热力学组分在链的横向半径的倒数的量级的较高波矢量处具有峰。在无限次，动态结构因子向静态结构因子的冻结分量松弛。在小波矢的限制下，松弛是扩散的，扩散常数等于拉伸链的平卡斯斑点的斯托克斯扩散常数。扩散常数在链的横向半径的倒数的数量级的波矢处显示出最小值。
We present a simple model for scattering properties of polyelectrolyte gels at swelling equilibrium. In the weak screening limit where the Debye-Huckel screening length is larger than the mesh size of the gel, the direct electrostatic interactions are negligible and the swelling is driven by the osmotic pressure of the counterions. The tension created by this pressure is transmitted through the crosslinks to the elastic chains which behave as isolated chains with an applied force at their end points. The structure factor of the gel can be split into a frozen component due to the average concentration heterogeneities and a thermodynamic component due to concentration fluctuations. The frozen component has a peak at a wavevector of the order of the mesh size of the gel, the thermodynamic component has a peak at a higher wavevector of the order of the inverse transverse radius of the chains. At infinite times the dynamic structure factor relaxes towards the frozen component of the static structure factor. In the limit of small wavevectors the relaxation is diffusive with a diffusion constant equal to the Stokes diffusion constant of the Pincus blobs of the stretched chains. The diffusion constant shows a minimum at a wavevector of the order of the inverse transverse radius of the chains.