Review on the key controls of designer copolymer-silica mesophase monoliths (HOM-type) with large particle morphology, ordered geometry and uniform pore dimension

This review introduces the extensive key factors of the design of mesostructured monoliths with two- and three-dimensional (2D and 3D) geometries and large particle morphologies. Simple strategy in terms of fabrication time (within 10 min) and composition phase domains was achieved by using an instant direct-templating method of lyotropic and microemulsion phases of a variety of triblock copolymer (EO_m-PO_n-EO_m) surfactants, as we recently reported in [33] and [34]. The synthetic strategy provides realistic control over a wide range of mesophase geometries, yet maintains the long-range structural ordering, and thus improved the simplicity, significant periodicity, and high uniformity of the resultant silica monoliths. Cubic mesophases, in particular, exhibit a wide variety of mesostructured geometries when the block copolymers were used as a structure-directing agent under acidic synthesis conditions. For example, triblock copolymer (P123, EO ₂₀PO₇₀EO₂₀) was used to fabricate 2D hexagonal (P6mm). Our synthesis protocol revealed that ordered 3D cubic (Fd3m), (Im3m), and (Ia3d) silica monoliths were also fabricated in large domain sizes by templating P123 copolymers. In general, key factors such as the degree of solubilization of the hydrocarbons (co-solvent), the copolymer concentrations used in the phase domains, and the copolymer molecular nature, such as EO/PO ratio, significantly affect the formation of mesostructured phases and their extended long-range ordering in the final replicas of the silica monolith frameworks. The remarkable structural findings of 2D and 3D frameworks, transparent monoliths, and micropores combined with large cage- and cylindrical-like mesopores might show their desirability in many applications.