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1.
Phys Chem Chem Phys ; 24(2): 902-913, 2022 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-34909809

RESUMO

The influence of the hard segment nature on the crystallization kinetics of multi-block thermoplastic polyurethanes containing poly(butylene adipate) (PBA) as a soft segment was investigated. Using a combination of FTIR spectroscopy, time-domain 1H nuclear magnetic resonance (TD-NMR), differential scanning calorimetry (DSC), fast-scanning calorimetry (FSC) and wide-angle X-ray diffraction (WAXS), it was shown that aliphatic, cycloaliphatic and aromatic diisocyanates affect the phase separation efficiency of soft and hard segments. The best phase separation efficiency was observed for a sample containing aliphatic diisocyanate due to the development of a hydrogen bond network. The thermal history, phase separation and the degree of ordering of the polyurethane determine the polymorphic behavior of melt-crystallized PBA. The formation of a partially-ordered mesophase of linear aliphatic polyurethane leads to an increase in the crystallization rate of PBA at room temperature and the formation of thermodynamically stable α-crystals. The presence of bulk cycloaliphatic and aromatic diol-urethane fragments prevents the phase separation of PBA, which crystallizes after slow cooling in a mixture of α- and ß-crystalline forms. The new nanocalorimetry technique allows the identification of a direct correlation between the phase separation and crystallization kinetics of the melt-crystallized PBA in a wide range of cooling rates - from 2 to 30 000 K s-1. Particularly, ultra-fast cooling suppresses the nucleation of the ß-phase of PBA resulting in slow crystallization of only α-modification at room temperature. The role of the polyurethane mesophase in the crystallization of the soft segment was discussed for the first time.

2.
Materials (Basel) ; 14(11)2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34206146

RESUMO

The structural evolution of multiblock thermoplastic polyurethane ureas based on two polydiols, poly(1,4-butylene adipate (PBA) and poly-ε-caprolactone (PCL), as soft blocks and two diisocyanites, 2,4-toluylene diisocyanate (TDI) and 1,6-hexamethylene diisocyanate (HMDI), as hard blocks is monitored during in situ deformation by small- and wide-angle X-ray scattering. It was shown that the urethane environment determines the crystal structure of the soft block. Consequently, two populations of crystalline domains of polydiols are formed. Aromatic TDI forms rigid domains and imposes constrains on the crystallization of bounded polydiol. During stretching, the TDI-polydiol domains reveal limited elastic deformation without reorganization of the crystalline phase. The constrained lamellae of polydiol form an additional physical network that contributes to the elastic modulus and strength of the material. In contrast, polydiols connected to the linear semi-flexible HMDI have a higher crystallization rate and exhibit a more regular lamellar morphology. During deformation, the HMDI-PBA domains show a typical thermoplastic behavior with plastic flow and necking because of the high degree of crystallinity of PBA at room temperature. Materials with HMDI-PCL bonding exhibit elastic deformation due to the low degree of crystallinity of the PCL block in the isotropic state. At higher strain, hardening of the material is observed due to the stress-induced crystallization of PCL.

3.
Materials (Basel) ; 14(11)2021 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-34071178

RESUMO

We report on formation of a bicontinuous double gyroid phase by a wedge-shaped amphiphilic mesogen, pyridinium 4'-[3″,4″,5″-tris-(octyloxy)benzoyloxy]azobenzene-4-sulfonate. It is found that this compound can self-organize in zeolite-like structures adaptive to environmental conditions (e.g., temperature, humidity, solvent vapors). Depending on the type of the phase, the structure contains 1D, 2D, or 3D networks of nanometer-sized ion channels. Of particular interest are bicontinuous phases, such as the double gyroid phase, as they hold promise for applications in separation and energy. Specially designed environmental cells compatible with grazing-incidence X-ray scattering and atomic force microscopy enable simultaneous measurements of structural parameters/morphology during vapor-annealing treatment at different temperatures. Such in-situ approach allows finding the environmental conditions at which the double gyroid phase can be formed and provide insights on the supramolecular structure of thin films at different spatial levels.

4.
J Phys Chem Lett ; 8(7): 1651-1656, 2017 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-28322051

RESUMO

We present an all-inorganic photoactive material composed of Ag2PbI4 and PbI2, which shows unexpectedly good photovoltaic performance in planar junction solar cells delivering external quantum efficiencies of ∼60% and light power conversion efficiencies of ∼3.9%. The revealed characteristics are among the best reported to date for metal halides with nonperovskite crystal structure. Most importantly, the obtained results suggest a possibility of reaching high photovoltaic efficiencies for binary and, probably, also ternary blends of different inorganic semiconductor materials. This approach, resembling the bulk heterojunction concept guiding the development of organic photovoltaics for two decades, opens wide opportunities for rational design of novel inorganic and hybrid materials for efficient and sustainable photovoltaic technologies.

5.
J Phys Chem Lett ; 8(6): 1211-1218, 2017 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-28220700

RESUMO

We report a careful and systematic study of thermal and photochemical degradation of a series of complex haloplumbates APbX3 (X = I, Br) with hybrid organic (A+ = CH3NH3) and inorganic (A+ = Cs+) cations under anoxic conditions (i.e., without exposure to oxygen and moisture by testing in an inert glovebox environment). We show that the most common hybrid materials (e.g., MAPbI3) are intrinsically unstable with respect to the heat- and light-induced stress and, therefore, can hardly sustain the real solar cell operation conditions. On the contrary, the cesium-based all-inorganic complex lead halides revealed far superior stability and, therefore, provide an impetus for creation of highly efficient and stable perovskite solar cells that can potentially achieve pragmatic operational benchmarks.

6.
J Phys Chem Lett ; 8(1): 67-72, 2017 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-27936746

RESUMO

We report here all inorganic CsPbI3 planar junction perovskite solar cells fabricated by thermal coevaporation of CsI and PbI2 precursors. The best devices delivered power conversion efficiency (PCE) of 9.3 to 10.5%, thus coming close to the reference MAPbI3-based devices (PCE ≈ 12%). These results emphasize that all inorganic lead halide perovskites can successfully compete in terms of photovoltaic performance with the most widely used hybrid materials such as MAPbI3.

7.
J Phys Chem Lett ; 7(21): 4353-4357, 2016 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-27758104

RESUMO

Here we report a systematic study of the Pb2+ substitution in the hybrid iodoplumbate MAPbI3 with a series of elements affecting optoelectronic, structural, and morphological properties of the system. It has been shown that even partial replacement of lead with Cd2+, Zn2+, Fe2+, Ni2+, Co2+, In3+, Bi3+, Sn4+, and Ti4+ results in a significant deterioration of the photovoltaic characteristics. On the contrary, Hg-containing hybrid MAPb1-xHgxI3 salts demonstrated a considerably improved solar cell performance at optimal mercury loading. This result opens up additional dimension in the compositional engineering of the complex lead halides for designing novel photoactive materials with advanced optoelectronic and photovoltaic properties.

8.
Adv Mater ; 28(28): 6003-10, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27172371

RESUMO

[3]-Radialene-based dopant CN6-CP studied herein, with its reduction potential of +0.8 versus Fc/Fc+ and the lowest unoccupied molecular orbital level of -5.87 eV, is the strongest molecular p-dopant reported in the open literature, so far. The efficient p-doping of the donor-acceptor dithienyl-diketopyrrolopyrrole-based copolymer having the highest unoccupied molecular orbital level of -5.49 eV is achieved. The doped films exhibit electrical conductivities up to 70 S cm(-1) .

9.
Chem Commun (Camb) ; 51(35): 7562-4, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25848656

RESUMO

We report the application of a statistical Suzuki-Miyaura polycondensation reaction for synthesis of a family of carbazole-fluorene-TTBTBTT terpolymers with tailored physical and optoelectronic properties. Organic bulk heterojunction solar cells based on the designed materials with optimal fluorene to carbazole ratios yielded reproducible power conversion efficiencies of 6.5-6.7%.

10.
Chem Commun (Camb) ; 50(57): 7639-41, 2014 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-24893780

RESUMO

Here we report a systematic investigation of indigo thin films grown on different dielectric underlayers. It has been revealed that aliphatic hydrocarbon chains serve as templates inducing the formation of a new crystal modification of indigo which possesses advanced charge transport properties and affords a dramatic improvement in the electrical performance of organic field-effect transistors.

11.
Chemphyschem ; 13(6): 1470-8, 2012 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-22407506

RESUMO

This paper reports on the synthesis and self-organizing properties of monodendrons consisting of L-alanine at the focal point and alkyl chains with different length at the periphery. The structures of thin films and monolayers are studied by temperature-resolved grazing-incidence X-ray diffraction and scanning force microscopy. The interplay between H-bonding and ordering of the alkyl chains results in a rich temperature-dependent phase behavior. The monodendrons form H-bonded stabilized clusters with the number of molecules depending on the length of the aliphatic chains and temperature. The clusters play the role of constitutive units in the subsequent self-assembly. Short alkyl chains allow the material to form thermodynamically stable crystalline phases. The molecules with longer side groups exhibit additional transitions from the crystalline phase to thermotropic columnar hexagonal or columnar rectangular liquid-crystalline phases. In monolayers deposited on highly ordered pyrolytic graphite, the materials show ordering similar to thin films. However, for the compound bearing hexadecyl chains the affinity of the alkyl groups to graphite dominates the self-assembly and thereby allows epitaxial growth of a 2D lattice with flat-on oriented molecules.


Assuntos
Alanina/química , Dendrímeros/síntese química , Alquilação , Varredura Diferencial de Calorimetria , Dendrímeros/química , Ligação de Hidrogênio , Microscopia de Força Atômica , Modelos Moleculares , Estrutura Molecular
12.
Adv Mater ; 24(7): 973-8, 2012 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-22259023

RESUMO

Septithiophene with endgroups designed to form liquid crystalline phases and allows controlled deposition of an electrically connected monolayer. Field effect mobilies mobilities of charge carriers and spectroscopic properties of the monolayer provide evidence of sustainable transport and delocalization of the excitation through intermolecular interactions within the layer.


Assuntos
Soluções/química , Tiofenos/química , Transistores Eletrônicos , Cristais Líquidos/química
13.
Chemphyschem ; 11(17): 3638-44, 2010 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-20979087

RESUMO

Herein, we describe the synthesis of a low-symmetry monodendron, 3,4-bis(dodecyloxy)-5-[3,4,5-tris(dodecyloxy)benzyloxy]benzoic acid, following a simple route which starts from gallic acid ethyl ester and does not require any protecting groups. The self-assembled structures formed by the compound in 3D and 2D were investigated by synchrotron X-ray scattering and scanning force microscopy (SFM). In 3D, the compound forms a stable crystalline phase with an orthorhombic lattice in which the alkyl chains connected to different benzene rings form crystalline and amorphous domains. Upon cooling from the isotropic melt the compound exhibits a monotropic smectic mesophase. In 100-nm-thick films on a neutral substrate the structure loses its biaxiality, adopting a hexagonal columnar structure with the columns oriented parallel to the substrate. By contrast, in ultrathin films on graphite the SFM likely reveals two crystal orientations, which can develop due to the epitaxial adsorption on the substrate of the alkyl chains pertinent to different benzene rings.

14.
Phys Chem Chem Phys ; 12(7): 1444-52, 2010 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-20126757

RESUMO

A wedge-shaped amphiphilic molecule, 3,4,5-tridodecyloxycinnamic acid, was used as a model system to explore the role of different constitutive elements of the chemical structure in the formation of 2D and 3D self-assemblies. The polar heads forming cyclic hydrogen-bonded dimers determine the two largest unit cell parameters, which depend only slightly on the dimensionality of the system (i.e. 2D versus 3D) and on the sample thermal history. By contrast, the structure of the alkyl side chains is very sensitive to the phase transformations, and is likely to be responsible for the rich polymorphic behaviour of the studied compound. Thus, in the monotropic SmC phase, the alkyl chains form a liquid-crystalline sub-lattice with hexagonal symmetry that can further crystallize either in a triclinic sub-cell (metastable crystalline phase) or in an orthorhombic sub-cell (stable crystalline phase). In 2D, at the interface with the graphite surface the molecular orientation is guided by the epitaxy. Although the largest lattice parameters are close to those in the bulk, the alkyl chains adopt a particular alternating orientation. In one molecule of the dimer, two alkyl chains have their molecular planes parallel to the substrate while the third chain is perpendicular to it, and the other way around for the other molecule of the dimer. To our knowledge, such alternating orientation of the alkyl chains in the monolayer is reported for the first time.

15.
Macromol Rapid Commun ; 30(1): 29-33, 2009 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-21706534

RESUMO

Films of polyaniline (PANI) featuring about 80% crystallinity and characterised with strong π-π stacking alignment parallel to the film surface have been obtained directly after the original synthesis upon simple drying of the aqueous PANI suspension. A strong anisotropy in the growth of the nano-sized crystals produced during the synthesis results in the formation of micrometer-length fibrils perpendicular to the film surface in the course of water evaporation. The regular intercalation of water molecules between the PANI chains seems to be crucial for their ordering throughout the synthesis and film formation.

16.
J Am Chem Soc ; 128(51): 16928-37, 2006 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-17177444

RESUMO

Complexes consisting of poly(4-vinylpyridine) and mesogenic wedge-shaped ligands 4'-[3",4",5"-tris(dodecyloxy)benzoyloxy]azobenzene-4-sulfonic acid and 4'-[3",4",5"-tris(octyloxy)benzoyloxy]azobenzene-4-sulfonic acid have been prepared with different monomer/ligand ratios. Upon protonation of the poly(4-vinylpyridine) chains by the wedge-shaped sulfonic acid molecules a hypsochromic and hyperchromic effect was observed with the pi-pi* transition of the azo-chromophor, allowing us to monitor the neutralization process by means of UV-vis spectroscopy in solution. The changes of the absorption characteristics implied a conformational change of the polymer backbone. In the bulk the interaction between pyridine and sulfonic acid moieties was proved by FT-IR spectroscopy. Polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction measurements were used to study the bulk structure of the complexes. The complexes formed a liquid crystalline lamellar phase at low degrees of substitution, while a hexagonal columnar mesophase was observed at degrees of neutralization of 80% and higher.

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