Kumar Rajeev, Muthukumar M
Department of Polymer Science and Engineering, Materials Research Science and Engineering Center, University of Massachusetts, Amherst, Massachusetts 01003, USA.
J Chem Phys. 2007 Jun 7;126(21):214902. doi: 10.1063/1.2737049.
The authors present a generalized theory of microphase separation for charged-neutral diblock copolymer melt. The stability limit of the disordered phase for salt-free melt has been calculated using random phase approximation (RPA) and self-consistent-field theory (SCFT). Explicit analytical free energy expressions for different classical ordered microstructures (lamellar, cylinder, and sphere) are presented. The authors demonstrate that the chemical mismatch required for the onset of microphase separation (chi*N) in charged-neutral diblock melt is higher and the period of ordered microstructures is lower than those for the corresponding neutral-neutral diblock system. Theoretical predictions on the period of ordered structures in terms of Coulomb electrostatic interaction strength, chain length, block length, and chemical mismatch between blocks are presented. SCFT has been used to go beyond the stability limit, where electrostatic potential and charge distribution are calculated self-consistently. Stability limits calculated using RPA are in perfect agreement with the corresponding SCFT calculations. Limiting laws for the stability limit and the period of ordered structures are presented and comparisons are made with an earlier theory. Also, transition boundaries between different morphologies have been investigated.
作者提出了一种关于带电-中性二嵌段共聚物熔体微相分离的广义理论。已使用随机相位近似（RPA）和自洽场理论（SCFT）计算了无盐熔体无序相的稳定性极限。给出了不同经典有序微结构（层状、柱状和球状）的显式解析自由能表达式。作者表明，带电-中性二嵌段熔体中微相分离起始所需的化学错配（χ*N）比相应的中性-中性二嵌段体系更高，且有序微结构的周期更低。给出了关于有序结构周期与库仑静电相互作用强度、链长、嵌段长度以及嵌段间化学错配的理论预测。SCFT已被用于超越稳定性极限，在该极限下自洽计算静电势和电荷分布。使用RPA计算的稳定性极限与相应的SCFT计算结果完全一致。给出了稳定性极限和有序结构周期的极限定律，并与早期理论进行了比较。此外，还研究了不同形态之间的转变边界。
