Self-assembled membranes are of vital importance in biological systems e.g. cellular and organelle membranes, however, more focus is being put on synthetic self-assembled membranes not only as an alternative for lipid membranes but also as an alternative for lithographic methods. More investigations move towards self-assembly processes because of the low-cost preparations, structural self-regulation and the ease of creating composite materials and tunable properties. The fabrication of new smart membrane materials via self-assembly is of interest for delivery vessels, size selective separation and purification, controlled-release materials, sensors and catalysts, scaffolds for tissue engineering, low dielectric constant materials for microelectronic devices, antireflective coatings and proton exchange membranes for polymer electrolyte membrane fuel cells. Polymers and nanoparticles offer the most straightforward approaches to create membrane structures. However, alternative approaches using small molecules or composite materials offer novel ultra-thin membranes or multi-functional membranes, respectively. Especially, the composite material membranes are regarded as highly promising since they offer the possibility to combine properties of different systems. The advantages of polymers which provide elastic and flexible yet stable matrices can be combined with nanoparticles being either inorganic, organic or even protein-based which offers pore-size control, catalytic activity or permeation regulation. It is therefore believed that at the interface of different disciplines with each offering different materials or approaches, the most novel and interesting membrane structures are going to be produced. The combinations and approaches presented in this review offer non-conventional self-assembled membrane materials which exhibit a high potential to advance membrane science and find more practical applications.

We report a combined directing effect of the simultaneously applied graphoepitaxy and electric field on the self-assembly of cylinder forming polystyrene-b-poly­(dimethylsiloxane) block copolymer in thin films. A correlation length of up to 20 μm of uniaxial ordered striped patterns is an order of magnitude greater than that produced by either graphoepitaxy or electric field alignment alone and is achieved at reduced annealing times. The angle between the electric field direction and the topographic guides as well as the dimensions of the trenches affected both the quality of the ordering and the direction of the orientation of cylindrical domains: parallel or perpendicular to the topographic features. We quantified the interplay between the electric field and the geometry of the topographic structures by constructing the phase diagram of microdomain orientation. This combined approach allows the fabrication of highly ordered block copolymer structures using macroscopically prepatterned photolithographic substrates.

Self‐assembled membranes offer a promising alternative for conventional membrane fabrication, especially in the field of ultrafiltration. Here, a new pore‐making strategy is introduced involving stimuli responsive protein‐polymer conjugates self‐assembled across a large surface area using drying‐mediated interfacial self‐assembly. The membrane is flexible and assembled on porous supports. The protein used is the cage protein ferritin and resides within the polymer matrix. Upon denaturation of ferritin, a pore is formed which intrinsically is determined by the size of the protein and how it resides in the matrix. Due to the self‐assembly at interfaces, the membrane constitutes of only one layer resulting in a membrane thickness of 7 nm on average in the dry state. The membrane is stable up to at least 50 mbar transmembrane pressure, operating at a flux of about 21 000–25 000 L m−2 h−1 bar−1 and displayed a preferred size selectivity of particles below 20 nm. This approach diversifies membrane technology generating a platform for “smart” self‐assembled membranes.

A detailed birefringence analysis of the effect of strong dc electric fields on the order−disorder transition temperature (T ODT ) of lamella forming block copolymers is reported. The setup presented here enabled the measurement of the T ODT with high temperature resolution while the birefringence measurements were nondestructive and straightforward compared to alternative methods. A downward shift in the transition temperature was found for all samples upon application of the electric field. The data indicate that the dominating parameter that evokes the mixing of block copolymers when exposed to electric fields is the difference in dielectric permittivity Δϵ between the block copolymer constituents. The extent to which the T ODT is shifted is furthermore influenced by the degree of polymerization N. Shifts in the transition temperature of up to 7 °C were found upon application of an electric field of 5 kV/mm.

Time- and temperature-resolved in situ birefringence measurements were applied to analyze the effect of nanoparticles on the electric field-induced alignment of a microphase separated solution of poly(styrene)-block-poly(isoprene) in toluene. Through the incorporation of isoprene-confined CdSe quantum dots the reorientation behavior is altered. Particle loading lowers the order-disorder transition temperature, and increases the defect density, favoring nucleation and growth as an alignment mechanism over rotation of grains. The temperature dependent alteration in the reorientation mechanism is analyzed via a combination of birefringence and synchrotron SAXS. The detailed understanding of the effect of nanoparticles on the reorientation mechanism is an important prerequisite for optimization of electric-field-induced alignment of block copolymer/nanoparticle composites where the block copolymer guides the nanoparticle self-assembly into anisotropic structures.

University of Bristol -Explore Bristol Research General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms J o u r n a l Na me We report the effect of electric field on the morphological transitions and ordering behavior of polyferrocenylethylmethylsilane block (PFEMS)-containing copolymers. By analyzing structures in swollen films of metalorganic sphere-and cylinder-forming diblock copolymers, as well as of 3-miktoarm polyisoprene-arm-polystyrene-arm-PFEMS (3µ-ISF) terpolymers, we decouple two types of responses to the electric field: an increase in the volume fraction of the PFEMS block by oxidation of the ferrocenyl groups inducing morphological transformation, and orientation of the dielectric interfaces of microdomains parallel to the electric field vector. In the case of 3µ-ISF, the former effect dominates the morphological behavior at high electric field strengths, leading to a well-ordered hexagonal dot pattern. Our results demonstrate multiple tunability of ordered microdomain morphologies, suggesting future applications in nanofabrication and surface patterning.

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