Graded porous inorganic materials derived from self-assembled block copolymer templates

Non-Equilibrium Block Copolymer Self-Assembly Based Porous Membrane Formation Processes Employing Multicomponent Systems

Porous polymer-derived membranes are useful for applications ranging from filtration and separation technologies to energy storage and conversion. Combining block copolymer (BCP) self-assembly with the industrially scalable, non-equilibrium phase inversion technique (SNIPS) yields membranes comprising periodically ordered top surface structures supported by asymmetric, hierarchical substructures that together overcome performance tradeoffs typically faced by materials derived from equilibrium approaches. This review first reports on recent advances in understanding the top surface structural evolution of a model SNIPS-derived system during standard membrane formation. Subsequently, the application of SNIPS to multicomponent systems is described, enabling pore size modulation, chemical modification, and transformation to non-polymeric materials classes without compromising the structural features that define SNIPS membranes. Perspectives on future directions of both single-component and multicomponent membrane materials are provided. This points to a rich and fertile ground for the study of fundamental as well as applied problems using non-equilibrium-derived asymmetric porous materials with tunable chemistry, composition, and structure.

Synthesis and Formation Mechanism of All-Organic Block Copolymer-Directed Templating of Laser-Induced Crystalline Silicon Nanostructures

This report describes the generation of three-dimensional (3D) crystalline silicon continuous network nanostructures by coupling all-organic block copolymer self-assembly-directed resin templates with low-temperature silicon chemical vapor deposition and pulsed excimer laser annealing. Organic 3D mesoporous continuous-network resin templates were synthesized from the all-organic self-assembly of an ABC triblock terpolymer and resorcinol-formaldehyde resols. Nanosecond pulsed excimer laser irradiation induced the transient melt transformation of amorphous silicon precursors backfilled in the organic template into complementary 3D mesoporous crystalline silicon nanostructures with high pattern fidelity. Mechanistic studies on laser-induced crystalline silicon nanostructure formation revealed that the resin template was carbonized during transient laser-induced heating on the milli- to nanosecond timescales, thereby imparting enhanced thermal and structural stability to support the silicon melt-crystallization process at temperatures above 1250 °C. Photoablation of the resin material under pulsed excimer laser irradiation was mitigated by depositing an amorphous silicon overlayer on the resin template. This approach represents a potential pathway from organic block copolymer self-assembly to alternative functional hard materials with well-ordered 3D morphologies for potential hybrid photovoltaics, photonic, and energy storage applications.

Host-guest interaction induced supramolecular amphiphilic star architecture and uniform nanovesicle formation for anticancer drug delivery

A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an α-cyclodextrin (α-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-β-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin.

An ultrathin 2D semi-ordered mesoporous silica film: co-operative assembly and application

A novel ultrathin silica film with semi-ordered fingerprint-like mesopores is synthesized with the aid of the dual templates of graphene oxide (go) and tri-block copolymer P123.

One-Pot Synthesis of Hierarchically Macro- and Mesoporous Carbon Materials with Graded Porosity

Hierarchically porous materials are becoming increasingly important in catalysis, separation, and energy applications due to their advantageous diffusion and flux properties. Here we present the synthesis of hierarchically macro- and mesoporous carbon materials with graded porosity from a one-pot fabrication route. Organic-polymeric hybrids of a carbon precursor and poly(isoprene)-block-poly(styrene)-block-poly(4-vinylpyridine) with graded porosity are obtained via coassembly and nonsolvent-induced phase separation. The membranes were carbonized at temperatures as high as 1100 °C with simultaneous decomposition of the block copolymer. The carbon materials show an open nanoporous top surface with narrow pore-size distribution that opens up into a graded macroporous support with increasing macropore size along the film normal and mesoporous walls, providing for highly accessible porosity with a large surface area of over 500 m² g^-1. Further, we expand the direct synthesis process to form well-dispersed metal nanoparticles (such as nickel and platinum) on the graded, hierarchically porous carbon materials. Our one-pot synthesis offers a facile approach to graded macro- and mesoporous carbons.