Control of gel swelling and phase separation of weakly charged thermoreversible gels by salt addition.
Control of gel swelling and phase separation of weakly charged thermoreversible gels by salt addition.
复制标题
通过添加盐来控制弱带电热可逆凝胶的凝胶膨胀和相分离。
DOI：
10.1021/ma061960u
复制
发表时间：
2007
期刊：
影响因子：
5.5
通讯作者：
Vernon,Brent
中科院分区：
文献类型：
--
作者：
Solis,FranciscoJ;Vernon,Brent
用带电单体掺杂热可逆聚合物凝胶提供了一种通过将凝胶的性质与可调离子环境相结合来控制相分离和胶凝条件的方法。我们分析了依赖的凝胶化和相分离的条件上的盐的量存在的平均场模型的弱电荷缔合聚合物。明确地认为，在平均场水平的离子和共离子存在，我们确定它们的浓度在不同的平衡相时，系统进行相分离。对于弱聚合物电荷，离子对体系自由能的熵贡献在确定相平衡位置中起着核心作用。在最简单的情况下，当负责凝胶形成的缔合相互作用独立于静电相互作用时，盐的加入改变聚合物平衡浓度并间接改变凝胶的可测量溶胀。我们构建了这些系统的相图，展示了共存区域的位置，凝胶-溶胶边界，以及连接线的位置。我们确定的共存区域内的凝胶的溶胀。我们的主要结果是，盐对弱电荷凝胶性质的影响可以通过对有效不渗透性参数χ的额外贡献来描述，该贡献与掺杂度的平方f2成正比，与添加盐浓度的平方成反比。
Doping of thermoreversible polymer gels with charged monomers provides a way to control phase separation and gelation conditions by coupling the properties of the gel with a tunable ionic environment. We analyze the dependence of the gelation and phase separation conditions on the amount of salt present using a mean field model of weakly charged associative polymers. The ions and co-ions present are explicitly considered at the mean field level, and we determine their concentrations in the different equilibrium phases when the system undergoes phase separation. For weak polymer charge, the entropic contributions of the ions to the free energy of the system play a central role in the determination of the location of phase equilibrium. In the simplest case, when the associative interaction responsible for gel formation is independent of the electrostatic interaction, the addition of salt changes the polymer equilibrium concentrations and indirectly changes the measurable swelling of the gel. We construct phase diagrams of these systems that exhibit the location of the coexistence region, the gel−sol boundary, and the location of the tie lines. We determine the swelling of the gel within the coexistence region. Our main result is that the effect of the salt on the properties of the weakly charged gel can be described through an extra contribution to the effective immiscibility parameter χ proportional to the square of the doping degreef2and to the inverse square of the added salt concentrations-2.