Grzetic Douglas J, Delaney Kris T, Fredrickson Glenn H
ACS Macro Lett. 2019 Aug 20;8(8):962-967. doi: 10.1021/acsmacrolett.9b00316. Epub 2019 Jul 19.
We study a salt-doped polarizable symmetric diblock copolymer using a recently developed field theory that self-consistently embeds dielectric response, ion solvation energies, and van der Waals (vdW) attractions via the incorporation of segment polarizabilities and fixed dipoles. This field theory is amenable to direct simulation via the complex Langevin sampling technique and, thus, requires no approximations beyond the phenomenology of the underlying molecular model. We measure the shift in the order-disorder transition (ODT) of a diblock copolymer with salt-loading in field-theoretic simulations and observe rich behavior in which solvation, dilution and charge screening effects compete to determine whether the ordered or disordered phase is stabilized. At low salt concentrations, the salt behaves as a selective solvent, localizing into the high-dielectric domains and stabilizing the ordered phase. At high salt concentrations, however, the salt localization vanishes due to charge screening effects, and the salt behaves as a nonselective solvent that screens vdW attractions and stabilizes the disordered phase.
我们使用一种最近开发的场论来研究一种盐掺杂的可极化对称二嵌段共聚物，该场论通过纳入链段极化率和固定偶极子，自洽地嵌入了介电响应、离子溶剂化能和范德华（vdW）吸引力。这种场论适用于通过复朗之万采样技术进行直接模拟，因此，除了基础分子模型的唯象学之外，不需要任何近似。我们在场论模拟中测量了盐负载下二嵌段共聚物的有序-无序转变（ODT）的位移，并观察到丰富的行为，其中溶剂化、稀释和电荷屏蔽效应相互竞争，以确定有序相还是无序相更稳定。在低盐浓度下，盐表现为选择性溶剂，定位于高介电域并稳定有序相。然而，在高盐浓度下，由于电荷屏蔽效应，盐的定位消失，盐表现为非选择性溶剂，屏蔽vdW吸引力并稳定无序相。
