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1.
Chem Commun (Camb) ; 2019 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-31799978

RESUMO

A new liquid crystalline honeycomb phase is reported, containing highly stretched giant hexagonal cells with two opposing walls spanned by three consecutive end-to-end H-bonded rods, the (3-1-1) hexagons.

2.
Artigo em Inglês | MEDLINE | ID: mdl-31765511

RESUMO

The single gyroid phase as well as the alternating double network gyroid, composed of two alternating single gyroid networks, hold a significant place in ordered nanoscale morphologies for their potential applications as photonic crystals, metamaterials and templates for porous ceramics and metals. Here we report the first alternating network cubic liquid crystals. They form through self-assembly of X-shaped polyphiles, where the glycerol-capped terphenyl rods lie on the gyroid surface while the semiperfluorinated and aliphatic side-chains fill their respective separate channel networks. This new self-assembly mode can be considered as a two-color symmetry-broken double gyroid morphology, providing a tailored way to fabricate novel chiral structures with sub-10 nm periodicities using achiral compounds.

3.
J Am Chem Soc ; 141(40): 15761-15766, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31529966

RESUMO

A dendronized perylene bisimide (PBI) that self-organizes into hexagonal arrays of supramolecular double helices with identical single-crystal-like order that disregards chirality was recently reported. A cogwheel model of self-assembly that explains this process was proposed. Accessing the highly ordered cogwheel phase required very slow heating and cooling or extended periods of annealing. Analogous PBIs with linear alkyl chains did not exhibit the cogwheel assembly. Here a library of sequence-defined dendrons containing all possible compositions of linear and racemic alkyl chains was employed to construct self-assembling PBIs. Thermal and structural analysis of their assemblies by differential scanning calorimetry (DSC) and fiber X-ray diffraction (XRD) revealed that the incorporation of n-alkyl chains accelerates the formation of the high order cogwheel phase, rendering the previously invisible phase accessible under standard heating and cooling rates. Small changes to the primary structure, as constitutional isomerism, result in significant changes to macroscopic properties such as melting of the periodic array. This study demonstrated how changes to the sequence-defined primary structure, including the relocation of methyl groups between two constitutional isomers, dictate tertiary and quaternary structure in hierarchical assemblies. This led to the discovery of a sequence that self-organizes the cogwheel assembly much faster than even the corresponding homochiral compounds and demonstrated that defined-sequence, which has long been recognized as a determinant for the complex structure of biomacromolecules including proteins and nucleic acids, plays the same role also in supramolecular synthetic systems.

4.
Chemistry ; 25(60): 13739-13747, 2019 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-31365148

RESUMO

Wedge-shaped molecules, such as dendrons, are among the most important building blocks for directed supramolecular self-assembly. Here we present a new approach aimed at widening the range and complexity of potential mesophases by introducing double-tapered mesogens. Two series of compounds are presented, both alkali metal salts (Li, Na, Cs) of 3,4,5-tris-alkoxybenzoic acid with a second tapered tris-alkoxyaryl group attached at the end of an alkoxy chain. The double-tapered compounds all display an unusual hexagonal columnar phase consisting of one ionic and three non-ionic columns per unit cell. The cation size has an unexpectedly drastic effect on unit cell size. Unlike most columnar phases, the current phases show unusually high dimensional stability on heating, and high stiffness in spite of being 80-85 % aliphatic, attributed to their molecular topology. The described approach may lead to co-assemblies of multifunctional materials, for example, parallel p- and n-semiconducting nanowires or parallel ionic and electronic conductors.

5.
Angew Chem Int Ed Engl ; 58(22): 7375-7379, 2019 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-30920713

RESUMO

The first single-diamond cubic phase in a liquid crystal is reported. This skeletal structure with the F d 3 ‾ m space group is formed by self-assembly of bolaamphiphiles with swallow-tailed lateral chains. It consists of bundles of π-conjugated p-terphenyl rods fused into an infinite network by hydrogen-bonded spheres at tetrahedral four-way junctions. We also present a quantitative model relating molecular architecture to the space-filling requirements of six possible bicontinuous cubic phases, that is, the single- and double-network versions of gyroid, diamond, and "plumber's nightmare".

6.
Chem Commun (Camb) ; 55(29): 4154-4157, 2019 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-30809626

RESUMO

X-Shaped bolapolyphiles, comprising a linear polyaromatic core with glycerol groups at each end and two chemically different and incompatible chains, fixed to it at opposite sides, were synthesized and found to self-assemble into honeycomb-type liquid crystalline phases with square symmetry. The polyaromatic π-conjugated rods form the cell walls and the resulting prismatic cells of sub-5 nm size are alternatively filled with perfluorocarbon (RF) and the carbosilane chains (RSi). The resulting structures can be represented as either a two-colour snub-square tiling with triangular and square cells or as a chessboard tiling of squares.

7.
Soft Matter ; 2018 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-30411766

RESUMO

Fan-shaped molecules with aromatic head-groups and two or more flexible pendant chains often self-assemble into columns that form columnar liquid crystals by packing on a 2d lattice. Such dendrons or minidendrons are essential building blocks in a large number of synthetic self-assembled systems and organic device materials. Here we report a new type of phase transition that occurs between two hexagonal columnar phases, Colh1 and Colh2, of Na-salt of 3,4,5-tris-dodecyloxy benzoic acid. Interestingly, the transition does not change the symmetry, which is p6mm in both phases, but on heating it involves a quantised drop in the number of molecules n in the cross-section of a column. The drop is from 4 to 3.5, with a further continuous decrease toward n = 3 as temperature increases further above Tc. The finding is based on evidence from X-ray diffraction. Using a transfer matrix formulation for the interactions within a column, with small additional mean field terms, we describe quantitatively the observed changes in terms of intermolecular forces responsible for the formation of supramolecular columns. The driving force behind temperature-induced molecular ejection from the columns is the increase in conformational disorder and the consequent lateral expansion of the alkyl chains. The asymmetry of the transition is due to the local order between 4-molecule discs giving extra stability to purely n = 4 columns.

8.
J Am Chem Soc ; 2018 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-30462922

RESUMO

Liquid quasicrystals (LQC) have been discovered in self-assembling benzyl ether, biphenylmethyl ether, phenylpropyl ether, biphenylpropyl ether and some of their hybrid dendrons and subsequently in block copolymers, surfactants and other assemblies. These quasiperiodic arrays, which lack long-range translational periodicity, are approximated by two Frank-Kasper periodic arrays, Pm3̅ n cubic (Frank-Kasper A15) and P42/ mnm tetragonal (Frank-Kasper σ), which have been discovered in complex soft matter in the same order and compounds. Poly(2-oxazoline)s dendronized with (3,4) nG1 minidendrons (where n denotes an alkyl chain, C nH2 n+1) self-organize into the Pm3̅ n cubic phase ( n = 14 and 15) and, as reported recently, the P42/ mnm tetragonal phase ( n = 16). However, no LQC of a poly(2-oxazoline) is yet known. Here we report the synthesis, structural and retrostructural analysis of a dendronized poly(2-oxazoline) with n = 17 which self-organizes not only into the LQC but also in the above two Frank-Kasper approximants. All three phases are observed from the same polymer within a very narrow range of degree of polymerization that corresponds to only five monomer repeat units (5 ≤ DP ≤ 10). The formation of the Pm3̅ n cubic, P42/ mnm tetragonal and LQC phases from a single polymer chain within such a narrow range of DP raises the questions of how and why each of these phases is self-organized. This system may provide a model for theoretical investigations into the self-organization of soft matter into Frank-Kasper and related periodic and quasiperiodic arrays.

9.
Phys Chem Chem Phys ; 20(39): 25268-25274, 2018 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-30276414

RESUMO

A modulated and conventional DSC study of the transitions between the twist-bend nematic (Ntb), regular nematic (N) and isotropic liquid (Iso) phases was performed on a series of difluoroterphenyl-based dimers with (CH2)n spacers; n = 5, 7, 9, 11. The enthalpy of Ntb-N transition decreases steeply with increasing n, while that of the N-Iso transition increases with n; hence, the greatest effect of increasing n is a lowering N phase enthalpy. Based on past and present X-ray scattering experiments, we estimate the average molecular conformation in the Ntb phase and perform torsion energy calculations on the spacer. From this, the lowering enthalpy of the N phase is attributed to the decreasing torsional energy cost of bringing the two terphenyls from an inclined twisted conformation in the Ntb phase, to almost parallel in the N phase. With increasing n the C-C bonds of the spacers twist less away from their trans conformation, thereby reducing the overall torsion energy of the N phase. It is speculated that the nearly continuous nature of the Ntb-N transition in n = 11 dimer is associated with the divergence of the helical pitch toward infinity which is intercepted by a final jump at the very weak (0.01 J g-1) first-order transition. Small-angle X-ray scattering results suggest similar local cybotactic layering in both nematic phases, with four sublayers, i.e. tails, mesogens, spacers, mesogens.

10.
Chem Commun (Camb) ; 54(87): 12306-12309, 2018 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-30277230

RESUMO

p-Terphenyl based Y-shaped bolapolyphiles self-assemble into liquid crystalline honeycombs with co-axial organization of the π-conjugated rods around columns filled by alkyl sidechains. In this new hexagonal honeycomb with P6/mmm symmetry the orientation of the π-conjugated rods is perpendicular to the tangential honeycombs formed at lower temperature or with longer chain length.

11.
J Am Chem Soc ; 140(41): 13478-13487, 2018 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-30238744

RESUMO

The supramolecular column is an archetypal architecture in the field of periodic liquid crystalline and crystalline arrays. Columns are generated via self-assembly, coassembly, and polymerization of monomers containing molecules shaped as discs, tapered, twin- and Janus-tapered, crowns, hat-shaped crowns, and fragments thereof. These supramolecular columns can be helical and therefore exhibit chirality. In contrast, spheres represent a fundamentally distinct architecture, generated from conical and crown-like molecules, which self-organize into body-centered cubic, Pm3̅ n cubic (also known as Frank-Kasper A15), and tetragonal (also known as Frank-Kasper σ) phases. Supramolecular spherical aggregates are not known to further assemble into a columnar architecture, except as an intermediate state between a columnar periodic array and a cubic phase. In the present work, a chiral dendronized cyclotetraveratrylene (CTTV) derivative is demonstrated to self-organize into a supramolecular column unexpectedly constructed from supramolecular spheres, with no subsequent transition to a cubic phase. Structural and retrostructural analysis using a combination of differential scanning calorimetry, X-ray diffraction (XRD), molecular modeling, and simulation of XRD patterns reveals that this CTTV derivative, which is functionalized with eight chiral first-generation minidendrons, self-organizes via a column-from-spheres model. The transition from column to column-from-spheres was monitored by circular dichroism spectroscopy, which demonstrated that both the supramolecular column and supramolecular spheres are chiral. This column-from-spheres model, which unites two fundamentally distinct self-assembled architectures, provides a new mechanism to self-organize supramolecular columnar architectures.

12.
Chemistry ; 24(60): 16072-16084, 2018 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-29939440

RESUMO

The dimensionality of self-assembled nanostructures plays an essential role for their properties and applications. Herein, an understanding of the transition from weakly to strongly coupled layers in soft matter systems is provided involving in-plane organized π-conjugated rods. For this purpose, bolaamphiphilic triblock molecules consisting of a rigid biphenyl core, polar glycerol groups at the ends, and a branched (swallow-tail) or linear alkyl or semiperfluoroalkyl chain in lateral position have been synthesized and investigated. Besides weakly coupled lamellar isotropic (LamIso ), lamellar nematic (LamN ) and sliding lamellar smectic phases (LamSm ), a sequence of three distinct types of strongly coupled (correlated) lamellar smectic phases with either centered (c2mm) or non-centered rectangular (p2mm) lattice and an intermediate oblique lattices (p2) were observed depending on chain length, chain branching and degree of chain fluorination. This new sequence is explained by the strengthening of the layer coupling and the competition between energetic packing constraints and the entropic contribution of either longitudinal or tangential fluctuations. This example of directed side chain engineering of small generic model compounds provides general clues for morphological design of two-dimensional and three-dimensionally coupled lamellar systems involving larger π-conjugated molecular rods and molecular or supramolecular polymers, being of actual interest in organic electronics and nanotechnology.

13.
Soft Matter ; 14(16): 3003-3011, 2018 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-29485649

RESUMO

The main-chain liquid crystal (LC) copolyethers in which the nematic-nematic phase transition was first experimentally observed were revisited and re-characterised. Grazing incidence X-ray scattering revealed that the low-T nematic (Ntb) phase could be highly aligned by shearing, more so than in previously studied bent LC dimers. This was evidenced by a four-point wide-angle X-ray scattering pattern, which originates from convolution of two tilt distributions. Through intensity simulation the orientational order parameter associated with each of the distributions, as well as the conical angle of the Ntb phase, was calculated. Information regarding the polymer chain conformation was obtained using polarised infrared spectroscopy. The findings suggest the average conformation of the chains is a helix, and that the bend angle between mesogenic units is inversely related to temperature. All experimental evidence, including a jump in birefringence at the Ntb-nematic (N) phase transition, shows that copolyether samples mirror the behaviour of bent LC dimers over the transition. This confirms that the low-T nematic phase in copolyethers is indeed the same as that in LC dimers, now known to be the Ntb. The unusual broadening of transition peaks in complex heat capacity, obtained by modulated DSC experiments, is discussed.

14.
Angew Chem Int Ed Engl ; 57(11): 2835-2840, 2018 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-29314461

RESUMO

The so-called smectic-Q (SmQ) liquid crystal phase was discovered in 1983 in rod-like molecules, but its structure remain unclear in spite of numerous attempts to solve it. Herein, we report what we believe to be the solution: A unique bicontinuous phase that is non-cubic and is made up of orthogonal twisted columns with planar 4-way junctions. While SmQ had only been observed in chiral compounds, we show that this chiral phase forms also in achiral materials through spontaneous symmetry breaking. The results strongly support the idea of a helical substructure of bicontinuous phases and long-range homochirality being sustained by helicity-matching at network junctions. The model also explains the triangular shape of double-gyroid domains growing within a SmQ environment. SmQ-forming materials hold potential for applications such as circularly polarized light emitters that require no alignment or asymmetric synthesis.

15.
J Am Chem Soc ; 140(5): 1805-1811, 2018 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-29156881

RESUMO

Honeycomb structure endows graphene with extraordinary properties. But could a honeycomb monolayer superlattice also be generated via self-assembly of colloids or nanoparticles? Here we report the construction of mono- and multilayer molecular films with honeycomb structure that can be regarded as self-assembled artificial graphene (SAAG). We construct fan-shaped molecular building blocks by covalently connecting two kinds of clusters, one polyoxometalate and four polyhedral oligomeric silsesquioxanes. The precise shape control enables these complex molecules to self-assemble into a monolayer 2D honeycomb superlattice that mirrors that of graphene but on the mesoscale. The self-assembly of the SAAG was also reproduced via coarse-grained molecular simulations of a fan-shaped building block. It revealed a hierarchical process and the key role of intermediate states in determining the honeycomb structure. Experimental images also show a diversity of bi- and trilayer stacking modes. The successful creation of SAAG and its stacks opens up prospects for the preparation of novel self-assembled nanomaterials with unique properties.

16.
Chem Commun (Camb) ; 54(2): 156-159, 2018 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-29215099

RESUMO

Three compounds with a bent rod-like aromatic core and with three alkoxy chains at each end were synthesised by click reaction. The compounds form a columnar liquid crystal phase with non-centrosymmetric trigonal p31m symmetry, the columns having a 3-arm star-like cross-section.

17.
Phys Chem Chem Phys ; 19(32): 21663-21671, 2017 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-28767115

RESUMO

In situ time-resolved small-angle X-ray scattering is introduced as a method to monitor the diffusion of a solvent in ceramic hollow nanoparticles (HNPs) supported by a polymer gel scaffold. Changes in the form factor were matched to discrete scattering models. A consecutive reaction kinetic model is used to analyze different stages of solvent diffusion. Rate constants and diffusion coefficients are extracted. By taking the diffusion of low molecular poly(ethylene glycol) in poly(ethylene oxide)-embedded HNPs as a model case, it was found that it took about 0.7 s for the solvent to diffuse through the 6 nm thick shell of HNPs and another 1.2 s to fill the inner cavity, while the diffusion coefficient was of the order of 1018 m2 s-1. The results demonstrate that the method can simultaneously measure solvent penetration into the polymer gel and into embedded sub-100 nm HNPs.

18.
J Phys Condens Matter ; 29(41): 414001, 2017 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-28737166

RESUMO

We performed an atomic force microscopy study of the dendron-based dodecagonal quasicrystal, the material that had been reported in 2004 as the first soft quasicrystal. We succeeded in orienting the 12-fold axis perpendicular to the substrate, which allowed the imaging of the quasiperiodic xy plane. Thus for the first time we have been able to obtain direct real-space information not only on the arrangement of the tiles, but also on their 'decorations' by the individual spherical micelles or 'nanoatoms'. The high-resolution patterns recorded confirm the square-triangle tiling, but the abundance of different nodes corresponds closely to random tiling rather than to any inflation rule. The previously proposed model of three types of decorated tiles, two triangular and one square, has been confirmed; the basic Frank-Kasper mode of alternating dense-sparse-dense-sparse layer stacking along z is confirmed too, each of the four sublayers being 2 nm thick. The consecutive dense layers are seen to be rotated by 90°, as expected. The 2 nm steps on the surface correspond to one layer of spheres, nonetheless with a dense layer always remaining on top, which implies a layer slip underneath and possibly the existence of screw dislocations.

19.
Soft Matter ; 13(22): 4122-4131, 2017 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-28548148

RESUMO

Using 2D X-ray diffraction and AFM we studied the configuration, in cylindrical confinement, of hexagonal columnar phases that anchor homeotropically, i.e. with the columns normal to the pore wall. A wide range of pore diameters, from 20 nm to 100 µm, were explored by employing anodic alumina membranes and glass capillaries. The compounds used were a small discotic, hexakis(hexyloxy)triphenylene (HAT6), a large discotic hexa-peri-hexabenzocoronene (HBC), and a T-shaped bolaamphiphile, forming a honeycomb-type columnar phase. It was found that in pores up to tens of µm in diameter the columns adopt the "logpile" configuration with parallel columns crossing the pore perpendicular to its axis. Starting with 20 nm pores, with increasing pore diameter up to 5 different configurations are observed, the sequence being the same for all three compounds in spite of their structural diversity. One of the {100} planes of the hexagonal logpile starts from being parallel to the pore axis, then rotates by 90° as the pore size increases, and eventually becomes tilted to the pore axis by (8.5 ± 1)° as the pore widens further. Finally, in glass capillaries of tens of µm and beyond, the columns become axially oriented, parallel to the capillary axis. This latter finding was particularly unexpected as common sense would suggest axial columns to be favoured by planar anchoring, where in fact, it was shown to be hard to achieve. The present findings should help in the design of low-dimensional semiconductor or ionic conductor devices based on oriented columnar phases.

20.
ACS Comb Sci ; 18(12): 723-739, 2016 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-27797481

RESUMO

Synthesis, structural, and retrostructural analysis of a library containing 16 self-assembling perylene (PBI), 1,6,7,12-tetrachloroperylene (Cl4PBI), naphthalene (NBI), and pyromellitic (PMBI) bisimides functionalized with environmentally friendly AB3 chiral racemic semifluorinated minidendrons at their imide groups via m = 0, 1, 2, and 3 methylene units is reported. These semifluorinated compounds melt at lower temperatures than homologous hydrogenated compounds, permitting screening of all their thermotropic phases via structural analysis to discover thermodynamically controlled helical crystallization from propeller-like, cogwheel, and tilted molecules as well as lamellar-like structures. Thermodynamically controlled helical crystallization was discovered for propeller-like PBI, Cl4PBI and NBI with m = 0. Unexpectedly, assemblies of twisted Cl4PBIs exhibit higher order than those of planar PBIs. PBI with m = 1, 2, and 3 form a thermodynamically controlled columnar hexagonal 2D lattice of tilted helical columns with intracolumnar order. PBI and Cl4PBI with m = 1 crystallize via a recently discovered helical cogwheel mechanism, while NBI and PMBI with m = 1 form tilted helical columns. PBI, NBI and PMBI with m = 2 generate lamellar-like structures. 3D and 2D assemblies of PBI with m = 1, 2, and 3, NBI with m = 1 and PMBI with m = 2 exhibit 3.4 Å π-π stacking. The library approach applied here and in previous work enabled the discovery of six assemblies which self-organize via thermodynamic control into 3D and 2D periodic arrays, and provides molecular principles to predict the supramolecular structure of electronically active components.


Assuntos
Cristalização , Imidas/química , Imidas/síntese química , Naftalenos/química , Perileno/química , Hidrocarbonetos Policíclicos Aromáticos/química , Hidrocarbonetos Policíclicos Aromáticos/síntese química , Técnicas de Química Combinatória/métodos , Estrutura Molecular , Estereoisomerismo , Termodinâmica
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