Alberto Concellón

Bio: Alberto Concellón is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Liquid crystal & Dendrimer. The author has an hindex of 11, co-authored 62 publications receiving 325 citations. Previous affiliations of Alberto Concellón include University of Zaragoza & Spanish National Research Council.

Light-Responsive Self-Assembled Materials by Supramolecular Post-Functionalization via Hydrogen Bonding of Amphiphilic Block Copolymers

Abstract: A new class of light-responsive supramolecular amphiphilic block copolymers (BCs) based on the association through multiple H-bonding between 4-isobutyloxyazobenzene motifs and 2,6-diacylaminepyridine units is reported. Block copolymers containing 2,6-diacylaminopyridine side units, as hydrophobic block, and poly(ethylene glycol), as a hydrophilic segment, were functionalized with either a carboxylic acid azodendron, via double H-bonding, or a thymine azobenzene, via triple H-bonding. The structural and thermal characterization of these supramolecular azo-copolymers in bulk and solution is presented. The work emphasizes the self-assembly of these supramolecular polymers in water and the study of their UV-light responsive properties by UV–vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), and synchrotron small-angle X-ray (SAXS). The present noncovalent postpolymerization functionalization strategy has provided stable self-assemblies in water with light responsive pro...

Proton-conductive materials formed by coumarin photocrosslinked ionic liquid crystal dendrimers

Abstract: In this work, we have successfully examined for the first time the use of ionic dendrimers as building blocks for the preparation of 1D and 2D proton conductive materials. For this purpose, a new family of liquid crystalline dendrimers has been synthesized by ionic self-assembly of poly(amidoamine) (PAMAM) dendrimers bearing 4, 8, 16, 32 or 64 NH2 terminal groups and a coumarin-containing bifunctional dendron. The noncovalent architectures were obtained by the formation of ionic salts between the carboxylic acid group of the dendron and the terminal amine groups of the PAMAM dendrimer. The liquid crystal properties have been investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). All the compounds exhibited mesogenic behavior with smectic A or hexagonal columnar mesophases depending on the generation of the dendrimer. Coumarin photodimerization was used as a crosslinking reaction to obtain liquid crystalline polymer networks. All the materials showed good proton conductive properties as the LC arrangement leads to the presence of ionic nanosegregated areas (formed by the ion pairs) that favor proton conduction.

Not Only Columns: High Hole Mobility in a Discotic Nematic Mesophase Formed by Metal-Containing Porphyrin-Core Dendrimers

Abstract: We report a new family of multifunctional liquid-crystalline porphyrin-core dendrimers that have coumarin functional groups around the porphyrin core. Porphyrin metalation strongly affects the photophysical properties, and therefore ZnII and CuII derivatives have also been prepared. All the synthesized dendrimers form a nematic discotic mesophase. Their high tendency for homeotropic alignment makes these dendrimers excellent candidates for device applications, owing to their easy processability, spontaneous alignment between electrodes, and self-healing of defects because of their dynamic nature. The charge mobility values of these materials are the highest ever reported for a nematic discotic phase. Moreover, these values are similar to the highest values reported for ordered columnar mesophases, and this shows that a supramolecular organization in columns is not necessary to achieve high charge mobility.

Dynamic Complex Liquid Crystal Emulsions.

Abstract: We report a new class of dynamically reconfigurable complex colloids comprising immiscible liquid crystals (LCs) and fluorocarbon oils. Producing stable spherical droplets requires the utilization of appropriately designed surfactants to reduce the high intrinsic surface tension between the LCs and the fluorocarbon oils that initially lead to nonspherical, "snowman-shaped" Janus droplets. After stabilizing the interfaces via surfactants, the LC droplet morphology can be dynamically switched between LC-in-fluorocarbon-in-water double emulsions (LC/F/W), spherical Janus emulsions, and inverted double emulsions (fluorocarbon-in-LC-in-water, F/LC/W) in response to changes in the surrounding surfactants. These stabilization methods can be extended to smectic LCs to create droplets with more complex internal arrangements and expand the range of LC emulsions that can be prepared. In addition, by using new mesogenic surfactants that control the LC director field at each LC interface, we prepare LC complex colloids exhibiting different internal configurations. The ability to control the LC anchoring conditions made it possible to create topological singularities as powerful templates for the precision assembly of antibodies at the droplets' interface. These dynamic LC complex colloids of controllable morphology and LC orientation are rich soft material platforms that will find utility in a variety of sensing applications.

Size-selective adsorption in nanoporous polymers from coumarin photo-cross-linked columnar liquid crystals

Abstract: We have prepared nanoporous polymers from columnar hexagonal hydrogen-bonded complexes, whose order is fixed by coumarin photoinduced [2 + 2] cycloaddition (photodimerization). Two different hydrogen-bonded complexes were used and consisted of a melamine (M) or tris(triazolyl)triazine (T) derivative acting as central templates and three peripheral carboxylic acids containing coumarin units. These coumarin units were employed for the cross-linking process by photodimerization in order to fix the LC arrangement. Template removal leads to the formation of self-standing nanoporous polymers keeping the columnar hexagonal order. Two nanoporous polymers with different pore diameters were obtained depending on size of the utilized template. These polymers with carboxylic acids at the pore surface demonstrate the ability to selectively adsorb certain molecules depending on their size. Moreover, after base treatment of the nanoporous polymers, they are able to adsorb cationic dyes over anionic and larger cations, d...

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

液晶物質の有機トランジスタへの展開 ; Liquid Crystals for Organic Thin Film Transistors

Abstract: Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V−1 s−1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.

Light to Shape the Future: From Photolithography to 4D Printing

Abstract: J.d.B. acknowledges the MINECO, the FSE, and the FEDER for funding through projects RYC‐2015‐18471 (Ramon y Cajal program) and CTQ2017‐84087. C.S.‐S. thanks the Spanish MICINN projects BIO2017‐84246‐C2‐1‐R, Gobierno de Aragon, and FEDER (EU).