A system can split into macroscopic regions with distinct local order parameters, densities or compositions. In a short-range system at phase coexistence, regions of two phases with means and volume fractions have spatial mean . Their interface contribution is subextensive, so their thermodynamic free-energy density is the corresponding convex combination of the phase densities. This can lie below the homogeneous-branch Landau free energy at the same . The equilibrium constrained order-parameter free energy is consequently convexified, with a straight coexistence segment described by the Maxwell construction. A nonconvex local potential remains useful for homogeneous branches, metastability and interfaces, but must not be identified with the full equilibrium constrained density throughout a coexistence interval.
Formation of finite-scale composition domains when complete macroscopic separation is frustrated, for example by the covalent connection of incompatible blocks in a diblock copolymer. Interfacial cost and chain entropy jointly select the domain scale.
Alternating sheet-like domains of the components of a microphase-separated material. In diblock systems the two layer thicknesses can be unequal and reflect unequal block fractions. Confinement, surface wetting and kinetic trapping can produce layered films outside the thermodynamic equilibrium bulk lamellar region.
A microdomain pattern of approximately parallel cylinders arranged on a two-dimensional hexagonal lattice in the other block's matrix. It is conventionally labelled H in many diblock phase diagrams. Cylinder orientation and defects are additional properties beyond the local morphology.
An ordered morphology in which a minority block forms approximately spherical domains in a continuous majority-block matrix. The lattice packing and phase stability depend on segregation strength, composition and chain statistics. The label S in a phase diagram denotes a morphology, not a spherical shape of the entire specimen.
The transition between a compositionally disordered state and an ordered microdomain state as effective segregation strength increases. The parameter combines unlike-segment interaction preference and chain length; its transition value depends on composition and model assumptions. A bulk thermodynamic equilibrium boundary is not by itself an evaporation or vitrification kinetic model.
A domain structure resembling lamellae pierced by an ordered array of perforations. It is distinct from an unperforated lamellar phase and from a double gyroid.
A bicontinuous domain morphology containing two interpenetrating, nonintersecting networks of one component within the other. In diblock copolymers it can appear between lamellar and cylindrical morphologies in part of the phase diagram.
Separation of a biomolecular mixture into compositionally distinct phases. Concentration dependence, partitioning and reversibility should be tested; a fluorescent punctum or recovery after bleaching alone does not establish the mechanism.
