Thermodynamics of 3D diamond-like epitaxial (film) morphologies on 1D modulated substrate: Weak crystallization theory

The permeability of diamond and other microphase-separated morphologies in copolymer films

A method is proposed for the theoretical assessment of potential membrane properties in materials based on microphase-separated block copolymer films subjected to the etching of one of the components. The concepts of topological permeability and connectivity contrast introduced by the authors are used to compare the percolation characteristics of simple cubic, diamond, and diamond-like morphologies compatible with the slit geometry and specified by a given distribution of the order parameter. The diamond-like morphology, which has the most promising transport characteristics, can be formed in a thin film of diblock copolymer AB placed on a chemically structured substrate. For this case, the quantitative analysis of permeability for certain parameters of the model system is carried out using the local distribution of A and B units calculated with the self-consistent field theory of microphase separation. The results obtained may be useful for the design of isoporous membranes based on block copolymers.

3D bicontinuous diamond-like morphologies in thin films of soluted block copolymers

As shown theoretically earlier via both weak segregation and self-consistent field theories, ordering of confined molten di- and tri-block copolymer morphologies in the presence of a proper 1D patterned substrate could induce the formation of 3D bicontinuous (in particular, diamond-like) morphologies (DLMs). The purpose of the present paper is to study, unlike the previous studies, how the stable DLMs are formed not in a melt but in a solution of symmetric diblock copolymers with a nonselective solvent that wets the thin film on the patterned substrate. It is shown, via a straightforward self-consistent field calculation of the total solution free energy for various competing phases, that the DLM could be formed in the solutions (with the solvent volume fraction of 0.5), which provides much faster thermodynamic equilibration of the solution as compared to the melt. The last circumstance can ease the production of stable DLMs in thin films of copolymers. The phase diagram describing the stable phases on the plane "the pattern period-the film thickness" is built.