Institut Charles Sadron, CNRS-UPR 22, Université de Strasbourg, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France.
J Chem Phys. 2013 Aug 7;139(5):054905. doi: 10.1063/1.4816469.
Effective potentials of interaction between solid non-adsorbing surfaces in semidilute or concentrated polymer solutions are calculated using two approaches: the numerical self-consistent-field theory (SCFT) and the analytical theory generalizing the ground-state dominance approximation by taking into account the finite chain-length (chain-end) effects (GSDE). A good agreement between the two approaches is demonstrated within the natural region of validity of the asymptotically exact GSDE theory. It is shown that in most cases the interaction potentials involve the short-range depletion attraction which is replaced by the polymer-mediated repulsion at longer separations ranging from roughly 10ξ to 3Rg (ξ is the concentration correlation length and Rg is the polymer coil gyration radius). For a given polymer concentration and molecular weight the highest repulsion energy barrier, Um, is predicted for ξ∕Rg ~ 0.2 and in the theta-solvent conditions. The fluctuation-induced (anti-Casimir) polymer-mediated repulsion forces are analyzed as well. It is shown that the overall polymer-mediated repulsion energy between naked spherical particles of radius Rc = 200 nm is typically not enough for their kinetic stabilization. There are, however, a few special cases where colloidal stability can be imparted by free polymers only.
数值自洽场理论（SCFT）和分析理论，该理论通过考虑有限链长（链端）效应（GSDE）推广了基态主导近似。在渐近精确 GSDE 理论的自然有效范围内，两种方法之间表现出良好的一致性。结果表明，在大多数情况下，相互作用势涉及短程耗尽吸引力，在更长的分离距离（约 10ξ至 3Rg，ξ 是浓度相关长度，Rg 是聚合物链旋半径）处，这种吸引力被聚合物介导的排斥所取代。对于给定的聚合物浓度和分子量，在θ溶剂条件下，ξ∕Rg ~ 0.2 时预测到最高的排斥能垒 Um。还分析了由涨落引起的（反 Casimir）聚合物介导的排斥力。结果表明，对于半径为 Rc = 200nm 的裸露球形粒子，聚合物介导的排斥能通常不足以实现其动力学稳定。然而，在少数特殊情况下，仅通过游离聚合物就可以赋予胶体稳定性。
