![]() ![]() An even broader variety of morphologies can be seen when the copolymers are dispersed 17, 18 in or exposed to selective solvents. The structure complexity rapidly increases when a third or multi-blocks are added 9. ![]() ![]() Spheres, cylinders and lamellae are the simplest equilibrium morphologies observed in solvent-free diblock copolymer systems 16. The morphology is guided by the thermodynamic interactions between blocks, the block-solvent affinities and by the block fractions. We have been using block copolymers for membrane formation with narrow pore size distribution 10, 11, 12 and tuned functionalization, and for the generation of biomimetic tridimensional structures 13, 14 block copolymers have been used as precursors, templates and base for the preparation of hybrid materials for energy conversion and storage 15. The rich morphology of block copolymer systems is extensively investigated and exploited for different purposes, other than particles formation. The particles pore geometry and distribution are in most case random, but especially interesting is the particle formation with a highly ordered morphology, which can be facilitated by a block copolymer self-assembly 8, 9. The total surface area and the full pore accessibility are essential for most applications. A crosslinking can additionally strengthen the particle stability 7. The particles’ size can be controlled by the polymerization, by the surfactant compositions in emulsions, or by using microfluidic 6 devices. They are generated by different methods, which involve nucleation induced by a non-solvent, emulsification 1, 2, suspension 3 and multistage polymerization, extractable porogens 4 and the selective etching of assembled block copolymers, as reviewed by Gokmen and Du Prez 5. Porous particles are relevant for chromatography, sorption-selective protein separations, catalysis, sensors and controlled drug delivery. The sample sectioning is done in situ, respectively by an ion beam or an ultramicrotome, SBF, a method so far mostly applied only to biological systems, was particularly highly informative to reproduce the ordered morphology of block copolymer particles with 32–54 nm nanopores and sampling volume (20 μm) 3. The samples are pre-sliced in an ultramicrotome. TEM has high resolution for details even smaller than 1 nm, but the imaged volume is relatively restricted (2.5 μm) 3. The capability of each method of 3D image reconstruction was demonstrated and their potential of application to other synthetic polymeric systems was discussed. The visualization of the complex ordered morphology requires complementary advanced methods of electron microscopy for 3D imaging, instead of a simple 2D projection: transmission electron microscopy (TEM) tomography, slice-and-view focused ion beam (FIB) and serial block face (SBF) scanning electron microscopy (SEM). Highly porous particles with internal triply periodic minimal surfaces were investigated for sorption of proteins. ![]()
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