Rigid Units Research Articles

High performance membranes containing rigid contortion units prepared by interfacial polymerization for CO2 separation

Polymeric membranes have been widely researched for several decades due to their good processability and low cost. Herein, high-performance thin-film composite (TFC) membranes were prepared by interfacial polymerization using N-methyldiethanolamine (MEDA), 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethylspirobisindane (TTSBI) and trimesoylchloride (TMC). The effects of segmental chain motion on the gas separation performance of the TFC membranes were investigated for the polymeric membranes featuring rigid and contorted sites along the polymer backbone by inducting TTSBI. The results suggested that the introduction of rigid and contorted structures improved the cavities in the membrane, impeded the transport of larger gas, and enhanced the diffusive selectivity. Therefore, the TFC membrane exhibited high permeance and high selectivity with CO2 permeance of about 1800 GPU and CO2/N2 selectivity of 370 at 0.11 MPa, which is a remarkable improvement in gas separation performance.

Geological risk characterization of traps and migration pathways for gas in an inverted salt basin

Inversion of the Lower Saxony Basin produced large-scale broad antiforms, hosting Germany's largest gas accumulations in stacked Permian and Triassic reservoir systems. Locally, however, several exploration and production wells failed in the upper Permian Zechstein-2-Carbonte (Ca2) due to missing reservoir (hiatus) or formation-water wet conditions despite of drilling the topmost position of the trap structure. Seismic interpretation indicates lateral shear of the structural topmost Ca2 reservoir by oblique inversion-related collision with the overlying rigid sandstone unit of the Triassic Bunter Formation (Fm.), triggering a halokinetic redistribution of Permian Zechstein (Z2-Z4) salt in between. Lateral shear was enabled along a thin Zechstein (Z1) salt decollement, underlying the Ca2 reservoir. This ultimately led to a full detachment of large intra-salt Ca2 allochthonous gas reservoirs (‘stringers’), leaving behind areas of Ca2 autochthonous absence (‘bald highs’). These kinematics triggered hydraulic connection and gas leakage from both, the ‘bald high’ margins of the autochthonous Ca2 and the Ca2 ‘stringers’ into the sandstone reservoir of the Bunter Fm. Methane-rich fluid inclusions in sub-horizontal tectonic veins and from within vertical stylolites sampled from cores of wells, which tested the Ca2 reservoir to be formation water-wet, proof gas leakage as a result of inversion. Identification criteria for gas leakage and reservoir presence have been established from this study to frame geological subsurface scenarios for pre-drill risk assessments of inverted settings. The generalized conclusion from this study is that the topmost position of structural highs in inverted salt basins may be actually exposed to the highest geological risk.

Characterizing flexibility and mobility in the natural mutations of the SARS-CoV-2 spikes

We use in silico modelling of the SARS-CoV-2 spike protein and its mutations, as deposited on the Protein Data Bank (PDB), to ascertain their dynamics, flexibility and rigidity. Identifying the precise nature of the dynamics for the spike proteins enables, in principle, the use of further in silico design methods to quickly screen for existing and novel drug molecules that might prohibit the natural protein dynamics. We employ a recent protein flexibility modeling approach, combining methods for deconstructing a protein structure into a network of rigid and flexible units with a method that explores the elastic modes of motion of this network, and a geometric modeling of flexible motion. Our results thus far indicate that the overall motion of wild-type and mutated spike protein structures remains largely the same.

Quinacridone-based small molecule acceptor as a third component in ternary organic solar cells

• A novel electron-accepting quinacridone derivative was used as a core of the acceptor. • The new acceptor CN-QA-RH presented a broad absorption in the solar spectrum and high crystallinity. • The ternary OSCs based on PBDB-T:PC 71 BM:CN-QA-RH demonstrated the PCE of 19.13% under LED (6500 K) illumination at 1000 lx. Ternary blend strategy has exhibited great prospect in organic solar cells (OSCs) due to the potential to boost the power conversion efficiency (PCE) by mainly enhancing the light absorption and morphology of the active layer. In particular, introduction of non-fullerene acceptor as the third component can overcome the intrinsic shortages of fullerene in the binary fullerene OSCs. Herein, an acceptor–donor-acceptor’-donor–acceptor(A-D-A’-D-A) type molecule, CN-QA-RH, containing a rigid acceptor unit quinacridone (QA) derivative as a central core, is designed and synthesized. The compound exhibits a wide absorption in the solar spectrum and good crystallinity. Both absorption and morphology of the active layer were improved by incorporating CN-QA-RH as the third component into PBDB-T:PC 71 BM. As a result, the best PCE of the ternary OSCs based on PBDB-T:PC 71 BM:CN-QA-RH was 8.96% while the binary OSCs based on PBDB-T:CN-QA-RH and PBDB-T:PC 71 BM exhibited PCEs of 2.66% and 7.84%, respectively. Moreover, the optimized ternary OSCs yielded a PCE of 19.13% under LED illumination at 1000 lx. Therefore, QA derivatives can be applied as non-fullerene acceptors with wide absorption and high crystallinity and demonstrated a great potential as the third component to construct highly efficient ternary OSCs for indoor light.

A self-powered intelligent glove for real-time human-machine gesture interaction based on piezoelectric effect of T-ZnO/PVDF film

In the emerging field of human-machine interaction, intelligent gesture recognition techniques have great application prospects. The traditional use of rigid and over-sized power units has restrained the development of wearable gesture recognition systems. Here, we present a self-powered intelligent glove based on piezoelectric motion sensor arrays for real-time gesture recognition. The system can be confortably worn on human hands, and mainly consists of three parts: a flexible piezoelectric motion sensor based on T-ZnO/PVDF film (T-ZnO, tetrapod ZnO nanostructures), a signal processing module for analyzing the sensing information, and a Bluetooth unit for wireless communication. The system can work without external power, and the piezoelectric output can act as both the energy source of the system and the sensing signal. The working mechanism can be attributed to the piezoelectric effect of T-ZnO/PVDF composites and with flexion and extension of the fingers, a series of pulse signals can be generated and converted into specific corresponding codes. The sensing signal can be wirelessly transmitted to smartphones through the Bluetooth unit, and the phone can recognize the codes corresponding to sign language actions and translate them. This work can potentially promote the development of the next generation of human-machine interaction systems and expand the scope of self-powered techniques and wearable electronics.

An anisotropic negative thermal expansion metamaterial with sign-toggling and sign-programmable Poisson’s ratio

AbstractObjectivesA mechanical metamaterial is introduced herein by drawing inspiration from an Aztec geometric pattern. This metamaterial deformation mechanism for Poisson’s ratio and Young’s modulus is based on non-rotating rhombi with rotating triangles, while the shear modulus analysis herein is based on rotating rhombi with non-rotating triangles, hence ‘partially rotating rigid units’.MethodsThe coefficient of thermal expansion was obtained by equating the potential energy expressions from the simple harmonic motion and from the principle of energy equipartition, while the effective-moduli were acquired by equating the strain energy from rotational stiffness with that from the strain energy of deformation based on an assumed homogenized continuum. Due to the zero and extreme Poisson’s ratio based on infinitesimal deformation, the finite approach was employed.ResultsResults indicate that the proposed metamaterial exhibits anisotropic negative thermal expansion with sign-switching Poisson’s ratio when applied stress along one axis is reversed. The Poisson’s ratio for loading in another axis is undefined under tension but can be programmed to exhibit either sign when compressed. The Young’s and shear moduli are directly governed by the rotational stiffness and strongly influenced by the extent of rotation, followed by the aspect ratio of the rotating units.ConclusionDue to its uniqueness, the currently considered mechanical metamaterial can be used under specific requirements which are difficult to be attained by other materials with negative properties.

Crystallographic parameterisation of distortions in the SOD framework in the sodalite and helvine groups: An analysis in condensed normal modes of an aristotype phase

AbstractCrystallographic distortions in the alternating aluminium and silicon tetrahedral framework of sodalite (Na8Al6Si6O24Cl2), and beryllium and silicon in helvine (Mn8Be6Si6O24S2), (framework designated SOD) are described in terms of a set of condensed normal mode amplitudes and phases derived from an ideal tetrahedron of a theoretical aristotype phase. For a sodalite-structured hettotype phase in space group $P{\overline 4} 3n$, these normal modes transform as the irreducible representations A1, E(α) and T1(z) of point-group ${\overline 4} 3m$, where to a good approximation A1 acts as a pure breathing mode, E(α) as a polyhedral distortive mode and T1(z) as a rigid unit rotation about the unique ${\overline 4}$ axis of the T-site under consideration. Parameterisation of the mode amplitudes in terms of low-order polynomials as a function of thermodynamic variable permits the crystal structure of sodalite-structured phases to be accurately interpolated at intermediate values of the thermodynamic variable. Published data for the high-temperature behaviour of sodalite have been re-analysed in terms of mode amplitudes which accurately reproduce the temperature dependence of the bond lengths, bond angles and the Al–O–Si inter-polyhedral angle. Full expressions for these derived structural parameters in terms of mode amplitudes and the lattice parameter are tabulated and agree with experimental results to within one estimated standard deviation of the experimental parameter. The potential for mode decomposition in lower symmetry SOD framework crystal structures is illustrated by deriving an aristotype structure for tugtupite (Na8Al2Be2Si8O24Cl2) at room temperature in space group $I{\overline 4}$.

Forearc density structure of the overriding plate in the northern area of the giant 1960 Valdivia earthquake

Abstract. The objective of this work is to analyse the density structure of the continental forearc in the northern segment of the 1960 Mw 9.6 Valdivia earthquake. Regional 2D and local 3D density models have been obtained from available gravity data in the area, complemented by new gravimetric stations. Models are constrained by independent geophysical and geological information and new TEM and MT soundings. The results show a segmentation of the continental wedge along and perpendicular to the margin, highlighting a high-density anomaly, below the onshore forearc basin, that limits the late Paleozoic–early Mesozoic metamorphic basement in the region where Chaitenia terrane has been proposed. A progressive landward shift of this anomaly correlates with the high slip patch of the giant 1960 Mw 9.6 Valdivia earthquake. Based on these results, we propose that the horizontal extension of the less rigid basement units conforming the marine wedge and Coastal Cordillera domain could modify the process of stress loading during the interseismic periods, and also that changes in position and extension of the late Paleozoic–early Mesozoic accretionary complex could be linked with the frictional properties of the interplate boundary. This analysis provides new evidence of the role of the overriding plate structure in the seismotectonic process in subduction zones.

Fusing rigid planar units to engineer twisting molecules as dual-state emitters

The fusion of multiple rigid, planar units into a highly twisting molecule is proposed as a molecular engineering strategy for synthesizing bright dual-state emitters. Applications such as mechanosensor and fluorescent probe have been demonstrated.

ОСОБЕННОСТИ ФУНКЦИОНИРОВАНИЯ ТЫ-/ВЫ-ФОРМ В РУССКОЙ И ИТАЛЬЯНСКОЙ ЛИНГВОКУЛЬТУРАХ

This paper presents the first part of research on the particularities of Ty-/Vy you/polite You, both 2nd person singular in the Russian and Italian languages. Far from the ambition of presenting the definitive account of the subject matter, the author identifies the main issues related to the investigation of these lexico-grammatical forms functioning in speech. Thus, such investigation of this matter implies researcher’s focus on: (1) particularities of Ty-/ Vy-functioning as the means of speech etiquette, specifically, in the functions of addressing, as well as in the concrete speech acts, in which the choice of the pronoun determines the grammatical realization of the statement (for instance, a request), (2) contextual meanings of these forms in cases when they serve as the means of an expressive function and the description of their peculiarities of their use in Russian in rigid phraseological units. At present, a contrastive analysis of concrete speech acts appears promising (and productive) method of interpretation of the national speech etiquette specifics. The paper presents the results of the study on the peculiarities of the use of the Ty-/Vy-forms as the means of speech etiquette in concrete situations of verbal communication. Comparative (contrastive) analysis of Russian and Italian allows to demonstrate the specifics of these two forms in either of the studied linguistic cultures. An additional focus of this paper is the investigation of the recent trends in the use of these forms in contemporary Italian. The study revealed the similarities and differences in Russian and Italian communicative behavior. The findings of the study can be applied in the context of teaching the etiquette of crosscultural communication and Russian-Italian translation.

Unfolding the terahertz spectrum of soft porous crystals: rigid unit modes and their impact on phase transitions

The flexibility of soft porous crystals is influenced by RUMs. Via static DFT calculations, the effect of building block substitutions on the RUMs in winerack MOFs is investigated, giving insight in the flexible nature of these frameworks.

Aza-triptycene-based homoleptic tris-cyclometalated iridium(III) complexes as highly efficient phosphors in green OLEDs

Three homoleptic tris-cyclometalated iridium (III) complexes (Ir1–Ir3) based on a rigid aza-triptycene unit have been synthesized via a novel one-pot method. The coordination arrangement of Ir2 was revealed by single X-ray structural analysis and the molecule showed a facial configuration. These complexes exhibited excellent thermal stability with Td of 454–520 °C. These complexes exhibit strong green phosphorescence emission with high quantum yields of over 70% due to the introduction of aza-triptycene skeleton with rigid steric hindrance reduced intermolecular interactions. Accordingly, the electroluminescence device based on Ir1, Ir2 and Ir3 exhibit high-brightness of 42194, 48807 and 46332 cd m−2, maximum luminous efficiency of 21.0, 24.7 and 28.5 cd A−1 and high EQE of 6.3, 6.8 and 8.9% at a high doping concentration of 30 wt%. Meanwhile, the non-doped green devices based on Ir1, Ir2 and Ir3 give high-brightness of 20571, 15407 and 10707 cd m−2 and luminous efficiency of 8.5, 9.5 and 5.4 cd A−1, respectively. These results suggest that these materials have potential application in OLEDs.

Soft-mode anisotropy in the negative thermal expansion material ReO3

We use a symmetry-motivated approach to analyse neutron pair distribution function data to investigate the mechanism of negative thermal expansion (NTE) in ReO$_3$. This analysis shows that the local structure of ReO$_3$ is dominated by an in-phase octahedral tilting mode and that the octahedral units are far less flexible to scissoring type deformations than the octahedra in the related compound ScF$_3$. These results support the idea that structural flexibility is an important factor in NTE materials, allowing the phonon modes that drive a volume contraction of the lattice to occupy a greater volume in reciprocal space. The lack of flexibility in ReO$_3$ restricts the NTE-driving phonons to a smaller region of reciprocal space, limiting the magnitude and temperature range of NTE. In addition, we investigate the thermal expansion properties of the material at high temperature and do not find the reported second NTE region. Finally, we show that the local fluctuations, even at elevated temperatures, respect the symmetry and order parameter direction of the observed $P4/mbm$ high pressure phase of ReO$_3$. The result indicates that the motions associated with rigid unit modes are highly anisotropic in these systems.

Ultrastable porous organic/inorganic polymers based on polyhedral oligomeric silsesquioxane (POSS) hybrids exhibiting high performance for thermal property and energy storage

In our work, we have been synthesized two-hybrid porous organic-inorganic microporous polymers (POIPs) through a simple and friendly Heck coupling reaction at a moderate temperature of cubic octavinylsilsesquioxane (OVS) with brominated fluorene (F–Br 2 ) and anthraquinone (A-Br 2 ); respectively, to afford POSS-F-POIP and POSS-A-POIP. FTIR, solid-state 13 C, and 29 Si NMR spectroscopy analyses were carried out to confirm the chemical structures of these POIP materials and the presence of POSS units within their framework. TGA measurements revealed that POSS-A-POIP possesses high thermal stability ( T d10 : 600 °C, and char yield: 83 wt%) due to the presence of rigid anthraquinone and POSS units. Furthermore, POSS-A-POIP features pseudocapacitor with high symmetry and high specific capacitance of 152.5 F g −1 at 0.5 A g −1 when compared with the POSS-F-POIP (36.2 F g −1 at 0.5 A g −1 ). The excellent energy storage performance of POSS-A-POIP could be attributed to the Faradaic reaction of anthraquinone and the π-conjugated system. • Two POSS-F-POIP and POSS-A-POIP were prepared through Heck coupling reaction. • The POSS-A-POIP possesses high thermal stability (T d10 : 600 °C, and char yield: 83 wt%). • The POSS-A-POIP features pseudocapacitor with high symmetry and high specific capacitance of 152.5 F g −1 at 0.5 A g −1 .

Auxetic Behavior and Other Negative Thermomechanical Properties from Rotating Rigid Units

Auxetics display the anomalous property of expanding laterally when uniaxially stretched, that is, a negative Poisson's ratio, a property that arises from 1) the presence of specific geometric features within the nano/macrostructure of the material and 2) amenable deformations in response to the applied stimulus. Herein, how ancient symmetrical esthetic artifacts have been transformed to functional auxetics through mechanisms that have ripened the field of “mechanical metamaterials” and “architected materials” in the last decades is explored. In particular, the important role and various implementations, both in 2D and 3D, of “rotating rigid units,” which range from “rotating squares” to much more complex renditions at various scales of structure, are looked at. The role of rotating rigid units to generate negative thermal expansion and negative compressibility is also delved into.

Extraordinary negative thermal expansion of monolayer biphenylene

Recently, the two-dimensional biphenylene with sp2-hybridized carbon atoms has been successfully fabricated by experiment [Science,372, 852 (2021)]. In this paper, the thermal expansion properties of monolayer biphenylene (MBP) are investigated by using the density functional theory combined with Grüneisen's theory. It is found that MBP exhibits anisotropic and negative in-plane thermal expansion and the negative thermal expansion is up to 1000 K. Although MBP and graphene have similar sp2 hybridized planar structure, the MBP exhibits significantly larger thermal contraction than graphene over a wide temperature range (0–1000K). At 300 K, the linear thermal expansion coefficient of MBP along the a-direction (1.10 × 10−5 K−1) is about three times that of graphene (3.7 × 10−6 K−1). The extraordinary negative thermal expansion not only originates from the ripple effect as in graphene only, but also the rigid unit modes are responsible for the thermal expansion behavior.

Odd-even effects in liquid crystals

ABSTRACT In this paper, odd-even effects in liquid crystals are briefly summarised. Based on the position and type of the repeating units, odd-even effects can be caused by methylene (CH2)k units either when terminating the LC molecules or separating monomers in dimers or polymers, or by the parity of the number of rigid mesogenic units separated by odd numbered methylene spacers. These odd-even effects are manifested themselves in the transition temperatures (mainly of the clearing point) and transition entropies, but they can also lead to alteration of phases, such as antiferroelectric or ferroelectric, or the appearance of tilted or orthogonal mesophases. These alternating phase and entropy properties then also lead to alternating secondary properties, such as in birefringence and elastic properties. In each category, we also discuss the theoretical considerations that can explain the observed odd-even effects.

The ISOTILT software for discovering cooperative rigid-unit rotations in networks of interconnected rigid units.

A user-friendly web-based software tool called 'ISOTILT' is introduced for detecting cooperative rigid-unit modes (RUMs) in networks of interconnected rigid units (e.g. molecules, clusters or polyhedral units). This tool implements a recently described algorithm in which symmetry-mode patterns of pivot-atom rotation and displacement vectors are used to construct a linear system of equations whose null space consists entirely of RUMs. The symmetry modes are first separated into independent symmetry-mode blocks and the set of equations for each block is solved separately by singular value decomposition. ISOTILT is the newest member of the ISOTROPY Software Suite. Here, it is shown how to prepare structural and symmetry-mode information for use in ISOTILT, how to use each of ISOTILT's input fields and options, and how to use and interpret ISOTILT output.

Theoretical and computational improvements to the algebraic method for discovering cooperative rigid-unit modes

A linear-algebraic algorithm for identifying rigid-unit modes in networks of interconnected rigid units has recently been demonstrated. This article presents a series of enhancements to the original algorithm, which greatly improve its conceptual simplicity, numerical robustness, computational efficiency and interpretability. The improvements include the efficient isolation of constraints, the observation of variable-block separability, the use of singular value decomposition and a quantitative measure of solution inexactness.

Crystal flex bases and the RUM spectrum

A theory of infinite spanning sets and bases is developed for the first-order flex space of an infinite bar-joint framework, together with space group symmetric versions for a crystallographic bar-joint framework ${{\mathcal {C}}}$. The existence of a crystal flex basis for ${{\mathcal {C}}}$ is shown to be closely related to the spectral analysis of the rigid unit mode (RUM) spectrum of ${{\mathcal {C}}}$ and an associated geometric flex spectrum. Additionally, infinite spanning sets and bases are computed for a range of fundamental crystallographic bar-joint frameworks, including the honeycomb (graphene) framework, the octahedron (perovskite) framework and the 2D and 3D kagome frameworks.