Oligo(phenyleneethynylene)s: Shape-Tunable Building Blocks for Supramolecular Self-Assembly

Oligo(phenyleneethynylene)s (OPEs) have attracted widespread attention due to their remarkable (opto)electronic and photophysical properties, which have enabled numerous applications. The versatile functionalization possibilities of OPEs make them unique candidates to form various shape-persistent geometries, including linear, triangular, rectangular, hexagonal and macrocyclic. However, as a result of this structural variety, it is oftentimes challenging to correlate molecular design with self-assembly properties. In this minireview, we have classified OPEs based on their molecular shapes and correlated them with their self-assembly behavior in solution. Particularly, we provide important insights into the aggregation propensity of the different molecular shapes and how to tune the association strength using various non-covalent interactions. Our classification will enable a better understanding of the structure-property correlation in OPEs, which is key to develop supramolecular functional materials.

Boron- and Oxygen-Doped π-Extended Helical Nanographene with Circularly Polarised Thermally Activated Delayed Fluorescence

Helical nanographenes have garnered substantial attention owing to their finely adjustable optical and semiconducting properties. The strategic integration of both helicity and heteroatoms into the nanographene structure, facilitated by a boron-oxygen-based multiple resonance (MR) thermally activated delayed fluorescence (TADF), elevates its photophysical and chiroptical features. This signifies the introduction of an elegant category of helical nanographene that combines optical (TADF) and chiroptical (CPL) features. In this direction, we report the synthesis, optical, and chiroptical properties of boron, oxygen-doped Π-extended helical nanographene. The π-extension induces distortion in the DOBNA-incorporated nanographene, endowing a pair of helicenes, (P)-B2NG, and (M)-B2NG exhibiting circularly polarized luminescence with glum of -2.3×10-3 and +2.5×10-3, respectively. B2NG exhibited MR-TADF with a lifetime below 5 μs, and a reasonably high fluorescence quantum yield (50 %). Our molecular design enriches the optical and chiroptical properties of nanographenes and opens up new opportunities in multidisciplinary fields.

Solvent-Free Organic Liquids: An Efficient Fluid Matrix for Unexplored Functional Hybrid Materials

ConspectusThe invention of solvent-free organic liquids (SOLs) was serendipitous. However, the curiosity-driven research in the later stage delivered new soft materials with exciting optical, and optoelectronic properties along with appealing physical characteristics suitable for the futuristic applications. A slight change in the molecular design resulted in a drastic change in the physical state of molecules demonstrating monomer-like features in the bulk. The basic idea of core isolation has been successful in delivering new SOLs with attractive functional properties. The unique fluid matrix associated with SOLs offers a tremendous opportunity for making hybrid materials by simple mixing. The chance to study the fundamentally important electron transfer, energy transfer, charge transfer interactions, triplet-state emissions, and even detailed NMR experiments in the solvent-free neat state is the major attraction of SOLs. Usually, solvents and their polarity control such molecular properties, and in the case of SOLs, it avoids the use of solvents to study such fundamentally important properties. Besides, SOLs protect the triplet emitters and excited state processes involving triplet states from quenchers and make the analysis possible under ambient conditions.Our effort in this direction was focused on tuning the ground and excited state properties by transforming conventional organic molecules to SOLs and further value addition by preparing the hybrid SOLs. We developed a series of hybrid SOLs, exploring room-temperature phosphorescence, thermally activated delayed fluorescence, charge or energy transfer between donor and acceptor SOLs, selective explosive sensing, etc. A slight variation in the chemical structure or optoelectronic properties of the individual components imparted exciting optical features for the hybrid SOLs. It includes nonemissive charge transfer, tunable emission exciplex, room temperature phosphorescence, and thermally activated delayed fluorescence SOLs. The liquid matrix of donor SOLs accommodated varying amounts of acceptor SOLs to tune the ground and excited state features. In all examples of donor-acceptor-based hybrid SOLs, even a low amount of acceptor, such as a donor-acceptor ratio of 1000:1, can cause pronounced optical properties. Hence, the evaluation of the optical properties of SOLs, especially, in the absence of solvents is so special that it avoids the interference of solvent molecules. Still, the major drawback of SOLs remains unsolved until we report polymerizable SOLs. Although a large variety of SOLs have been reported in the literature, the long-lasting problem of surface stickiness of SOLs was resolved by polymerizable SOLs. It enabled the development of flexible, foldable, and stretchable large-area luminescent films suitable for lighting and display devices. In this Account, we summarize our work on SOLs, hybrid SOLs, polymerizable SOLs, and the application of SOLs in selective sensing of explosives. Finally, an outlook on the feasibility of luminescent polymerizable SOLs in futuristic applications is provided.

Isomer Effect on Energy Storage of π-Extended S-Shaped Double[6]Heterohelicene

Recently, chiral and nonplanar cutouts of graphene have been the favorites due to their unique optical, electronic, and redox properties and high solubility compared with their planar counterparts. Despite the remarkable progress in helicenes, π-extended heterohelicenes have not been widely explored. As an anode in a lithium-ion battery, the racemic mixture of π-extended double heterohelical nanographene containing thienothiophene core exhibited a high lithium storage capability, attaining a specific capacity of 424 mAh g-1 at 0.1 A g-1 with excellent rate capability and superior long-term cycling performance over 6000 cycles with negligible fade. As a first report, the π-extended helicene isomer (PP and MM), with the more interlayer distance that helps faster diffusion of ions, has exhibited a high capacity of 300 mAh g-1 at 2 A g-1 with long-term cycling performance over 1500 cycles compared to the less performing MP and PM isomer and racemic mixture (150 mAh g-1 at 2 A g-1 ). As supported by single-crystal X-ray analysis, a unique molecular design of nanographenes with a fixed (helical) molecular geometry, avoiding restacking of the layers, renders better performance as an anode in lithium-ion batteries. Interestingly, the recycled nanographene anode material displayed comparable performance.

Polymerizable Solvent-free Organic Liquids: A New Approach for Large Area Flexible and Foldable Luminescent Films

The high demand for light-emitting and display devices made luminescent organic materials as attractive candidates. Solvent-free organic liquids are one of the promising emitters among them due to the salient features. However, the inherent limitations of forming sticky and noncurable surfaces must be addressed to become an alternate emitter for large-area device applications. Herein, we functionalized solvent-free organic liquids having monomeric emission in bulk with polymerizable groups to improve the processability. The polymerizable group on carbazole, naphthalene monoimide, and diketopyrrolopyrrole-based solvent-free liquid emitters enabled on-surface polymerization. These emitters alone and in combinations can be directly coated on a glass substrate without the help of solvents. Subsequent photo or thermal polymerization leads to stable, non-sticky, flexible, foldable, and free-standing large-area films with reasonably high quantum yield. Our demonstration of the tunable and white light-emitting films using polymerizable solvent-free liquids might be a potential candidate in flexible/foldable/stretchable electronics. The new concept of polymerizable liquid can be extended to other functional features suitable for futuristic applications.

Operando neutron diffraction reveals mechanisms for controlled strain evolution in 3D printing

Residual stresses affect the performance and reliability of most manufactured goods and are prevalent in casting, welding, and additive manufacturing (AM, 3D printing). Residual stresses are associated with plastic strain gradients accrued due to transient thermal stress. Complex thermal conditions in AM produce similarly complex residual stress patterns. However, measuring real-time effects of processing on stress evolution is not possible with conventional techniques. Here we use operando neutron diffraction to characterize transient phase transformations and lattice strain evolution during AM of a low-temperature transformation steel. Combining diffraction, infrared and simulation data reveals that elastic and plastic strain distributions are controlled by motion of the face-centered cubic and body-centered cubic phase boundary. Our results provide a new pathway to design residual stress states and property distributions within additively manufactured components. These findings will enable control of residual stress distributions for advantages such as improved fatigue life or resistance to stress-corrosion cracking.

Health inequities around gender, disability and internal migration: are local governments doing enough

SETTING

The Kerala health system in India has more than 25 years of decentralised implementation experience. Decentralization could assist in addressing health disparities such as gender, disability, and migration.

OBJECTIVE

To explore how inequity issues comprising gender, disability and internal migrations were being addressed at present by the decentralised Kerala health system.

DESIGN

Our approach was qualitative, using document review, key informant interviews and in-depth interviews with policy makers, health staff and other stakeholders.

RESULTS

Gender aspects were incorporated into planning and budgeting, with 10% funds earmarked for women. Projects were gender-specific to women, and within conventional social roles of livelihood, welfare or reproductive health. Recently, transgender focused projects were also initiated. Schemes for people with disabilities remained welfare-centric and driven by top-down policies. The local governments performed beneficiary identification and benefit disbursal. Migrant health aspects were focused on infectious diseases surveillance and later living conditions of migrant workers.

CONCLUSION

The importance that health systems place on socioeconomic determinants of health and fundamental human rights is reflected in the health interventions for marginalised communities. In Kerala, there is now a passive application of central rules and a reluctance to utilise local platforms. Changing this is a necessary condition for achieving equal development.

Oligothiophene-Ring-Strapped Perylene Bisimides: Functionalizable Coaxial Donor-Acceptor Macrocycles

Aesthetic designs from nature enable new knowledge to be gained and, at the same time, inspire scientific models. In this context, multicomponent macrocycles embody the advantage of precisely positioning the structural units to achieve efficient communication between them. However, the construction of a functionalizable macrocycle for ultrafast charge separation and stabilization has not been attempted. Herein, we report the synthesis, crystal structure, and transient absorption of a new functionalizable macrocycle consisting of an oligothiophene-ring-strapped perylene bisimide. Transient absorption results point to a sequential improvement in charge separation and stabilization from the macrocycle to the corresponding linear dimer and 2D polymer due to the unique design. Our macrocycle design with a supportive spatial arrangement of the donor and acceptor units will inspire the development of more complex synthetic systems with exciting electron-transfer and charge-separation features.

Donor-acceptor based solvent-free organic liquid hybrids with exciplex emission and room temperature phosphorescence

Solvent-free organic liquids are well-known for their excellent luminescence features. Hence, the recent developments in this area have marked them as potential emitters with high quantum yield and enhanced processability. The support of an available liquid matrix enables doping to deliver hybrid liquids with intriguing luminescence features. In this direction, we report solvent-free liquid donor-acceptor pairs with exciplex emission and room temperature phosphorescence at very low acceptor loading. The underlying weak intermolecular interactions have been revealed by 2D NMR techniques and theoretical calculations. The formation of large-area thin films by exciplex and phosphorescent liquid hybrids will encourage the development of scalable lighting and display materials.

An excimer to exciplex transition through realization of donor-acceptor interactions in luminescent solvent-free liquids

Luminescent solvent-free organic liquids are known for their enhanced quantum yield, color tunability, and availability of a matrix for other dopants to generate hybrid luminescent materials with improved features for newer applications. Herein, we report a donor-acceptor based luminescent "exciplex liquid" by utilizing the slightly different electron affinity of the acceptor molecules. A red-shifted broad exciplex emission exhibited by the donor-acceptor pair even at a lower concentration of the acceptor (0.001 equiv.) indicates high efficiency in the solvent-free state. A detailed NMR study revealed weak intermolecular interactions between the donor and acceptor in the solvent-free matrix that stabilizes the exciplex liquid. The failure of structurally similar solid counterparts to form an exciplex confirms the advantage of the available supportive liquid matrix. Besides, the luminescent exciplex liquid is found efficient in sensing application, which is unachievable by either the individual liquids or their solid counterparts. Here, a transition of a donor-acceptor pair from a solid to solvent-free liquid results in a new hybrid liquid that can be an alternative for solid sensor materials.

Microstructure and properties of additively manufactured Al-Ce-Mg alloys

Additive manufacturing of aluminum alloys is largely dominated by a near-eutectic Al-Si compositions, which are highly weldable, but have mechanical properties that are not competitive with conventional wrought Al alloys. In addition, there is a need for new Al alloys with improved high temperature properties and thermal stability for applications in the automotive and aerospace fields. In this work, we considered laser powder bed fusion additive manufacturing of two alloys in the Al–Ce–Mg system, designed as near-eutectic (Al–11Ce–7Mg) and hyper-eutectic (Al–15Ce–9Mg) compositions with respect to the binary L → Al + Al₁₁Ce eutectic reaction. The addition of magnesium is used to promote solid solution strengthening. A custom laser scan pattern was used to reduce the formation of keyhole porosity, which was caused by excessive vaporization due to the high vapor pressure of magnesium. The microstructure and tensile mechanical properties of the alloys were characterized in the as-fabricated condition and following hot isostatic pressing. The two alloys exhibit significant variations in solidification structure morphology. These variations in non-equilibrium solidification structure were rationalized using a combination of thermodynamic and thermal modeling. Both alloys showed higher yield strength than AM Al-10Si-Mg for temperatures up to 350 °C and better strength retention at elevated temperatures than additively manufactured Scalmaloy.

Efficient metal-free organic room temperature phosphors

An innovative transformation of organic luminescent materials in recent years has realised the exciting research area of ultralong room-temperature phosphorescence. Here the credit for the advancements goes to the rational design of new organic phosphors. The continuous effort in the area has yielded wide varieties of metal-free organic systems capable of extending the lifetime to several seconds under ambient conditions with high quantum yield and attractive afterglow properties. The various strategies adopted in the past decade to manipulate the fate of triplet excitons suggest a bright future for this class of materials. To analyze the underlying processes in detail, we have chosen high performing organic triplet emitters that utilized the best possible ways to achieve a lifetime above one second along with impressive quantum yield and afterglow properties. Such a case study describing different classes of metal-free organic phosphors and strategies adopted for the efficient management of triplet excitons will stimulate the development of better candidates for futuristic applications. This Perspective discusses the phosphorescence features of single- and multi-component crystalline assemblies, host-guest assemblies, polymers, and polymer-based systems under various classes of molecules. The various applications of the organic phosphors, along with future perspectives, are also highlighted.

Aggregation-induced phosphorescence of an anthraquinone based emitter

Room temperature phosphorescence (RTP) of metal-free organic molecules is a hot topic of current research interest. RTP can be enhanced through aggregation, crystallization, and the support of polymers and host-guest assemblies. The characteristics of highly phosphorescent aggregates formed from conventional chromophores make them ideal candidates for many potential applications. In this direction, we focused on the aggregation-induced phosphorescence of an anthraquinone derivative AqC6 in solution and in crystal state. The weakly emissive dilute solution exhibits a tunable emission with enhanced intensity and room temperature phosphorescence by increasing the concentration and solvent-antisolvent combination. The enhanced phosphorescence of crystals has been recreated in the solution by making use of aggregation. Interestingly, the support of PMMA enabled AqC6 to achieve enhanced processability, phosphorescence lifetime (174 ms) and quantum yield (5%).

Self-Assembled Helical Arrays for the Stabilization of the Triplet State

Room-temperature phosphorescence of metal and heavy atom-free organic molecules has emerged as an area of great potential in recent years. A rational design played a critical role in controlling the molecular ordering to impart efficient intersystem crossing and stabilize the triplet state to achieve room-temperature ultralong phosphorescence. However, in most cases, the strategies to strengthen phosphorescence efficiency have resulted in a reduced lifetime, and the available nearly degenerate singlet-triplet energy levels impart a natural competition between delayed fluorescence and phosphorescence, with the former one having the advantage. Herein, an organic helical assembly supports the exhibition of an ultralong phosphorescence lifetime. In contrary to other molecules, 3,6-phenylmethanone functionalized 9-hexylcarbazole exhibits a remarkable improvement in phosphorescence lifetime (>4.1 s) and quantum yield (11 %) owing to an efficient molecular packing in the crystal state. A right-handed helical molecular array act as a trap and exhibits triplet exciton migration to support the exceptionally longer phosphorescence lifetime.

Boron-Conjugated Pyrenes as Fluorescence-Based Molecular Probes and Security Markers

Boron-embedded aromatic hydrocarbons are a class of molecules known for their distinct electronic and/or optoelectronic properties and are thus suitable for many potential applications. Among those, boronic ester and acid containing molecules have been widely used for sensing and molecular recognition applications, respectively. We compared the sensing and molecular recognition properties of two boron-containing pyrene derivatives for fluoride and glucose sensing applications. The presence of four boronate ester groups enabled fluoride ion sensing at the μM level. The boronic acid derivative is very selective towards glucose compared to other saccharides. Furthermore, we used the mechano-responsive fluorescence changes and self-assembly of these derivatives, respectively, for fluorescence-based inkless and ink (water)-based writing in invisible security labeling applications.

Imidazole-Linked Crystalline Two-Dimensional Polymer with Ultrahigh Proton-Conductivity

Proton-exchange membrane fuel cells are promising energy devices for a sustainable future due to green features, high power density, and mild operating conditions. A facile proton-conducting membrane plays a pivotal role to boost the efficiency of fuel cells, and hence focused research in this area is highly desirable. Major issues associated with the successful example of Nafion resulted in the search for alternate proton conducting materials. Even though proton carrier loaded crystalline porous organic frameworks have been used for proton-conduction, the weak host-guest interactions limited their practical use. Herein, we developed a crystalline 2D-polymer composed of benzimidazole units as the integral part, prepared by the condensation of aryl acid and diamine in polyphosphoric acid medium. The imidazole linked-2D-polymer exhibits ultrahigh proton conductivity (3.2 × 10^-2 S cm^-1) (at 95% relative humidity and 95 °C) in the pristine state, which is highest among the undoped porous organic frameworks so far reported. The present strategy of a crystalline proton-conducting 2D-polymer will lead to the development of new high performing crystalline solid proton conductor.

Correction: Cascade energy transfer and tunable emission from nanosheet hybrids: locating acceptor molecules through chiral doping

Correction for 'Cascade energy transfer and tunable emission from nanosheet hybrids: locating acceptor molecules through chiral doping' by Goudappagouda et al., Chem. Commun., 2017, 53, 7072-7075.

Paintable Room-Temperature Phosphorescent Liquid Formulations of Alkylated Bromonaphthalimide

Organic phosphors have been widely explored with an understanding that crystalline molecular ordering is a requisite for enhanced intersystem crossing. In this context, we explored the room-temperature phosphorescence features of a solvent-free organic liquid phosphor in air. While alkyl chain substitution varied the physical states of the bromonaphthalimides, the phosphorescence remained unaltered for the solvent-free liquid in air. As the first report, a solvent-free liquid of a long swallow-tailed bromonaphthalimide exhibits room-temperature phosphorescence in air. Doping of the phosphor with carbonyl guests resulted in enhanced phosphorescence, and hence a large-area paintable phosphorescent liquid composite with improved lifetime and quantum yield was developed.

Charge transfer liquid: a stable donor–acceptor interaction in the solvent-free liquid state

A new charge transfer solvent-free liquid having high stability even with donor–acceptor ratio of 1000 : 1 is demonstrated.

A squaraine-linked metalloporphyrin two-dimensional polymer photocatalyst for hydrogen and oxygen evolution reactions

A squaraine–metalloporphyrin 2D-polymer based bifunctional catalyst for photocatalytic water splitting.

Correction: Conducting nanofibres of solvatofluorochromic cyclohexanetrione–dithiolylidene-based C3 symmetric molecule

Correction for ‘Conducting nanofibres of solvatofluorochromic cyclohexanetrione–dithiolylidene-based C₃ symmetric molecule’ by Kilingaru I. Shivakumar et al., Chem. Commun., 2018, 54, 212–215.

Conducting nanofibres of solvatofluorochromic cyclohexanetrione-dithiolylidene-based C3 symmetric molecule

We report a novel set of easily tailorable C₃ symmetric molecules with a π-extended core and adorned with different thioalkyl groups, exhibiting solvatofluorochromic and amphoteric redox behaviour. The nearly planar core exhibits intermolecular face-to-face π-stacking, SS and intramolecular SO interactions. Current-sensing atomic force microscopy studies revealed a high conductivity of ∼0.15 mS cm^-1 in the undoped J-aggregate nanofibres of the thiopropyl appended gelator.

Mixed-Stack Charge Transfer Crystals of Pillar[5]quinone and Tetrathiafulvalene Exhibiting Ferroelectric Features

Ferroelectric materials find extensive applications in the fabrication of compact memory devices and ultra-sensitive multifunctional detectors. Face-to-face alternate stacking of electron donors and acceptors effectuate long-range unidirectional ordering of charge-transfer (CT) dipoles, promising tunable ferroelectricity. Herein we report a new TTF-quinone system-an emerald green CT complex consisting pillar[5]quinone (P5Q) and tetrathiafulvalene (TTF). The CT crystals, as determined by single crystal synchrotron X-ray diffraction, adopt a 1:1 mixed-stack arrangement of donor and acceptor with alternating dimers of TTF and 1,4-dioxane encapsulated P5Q. The TTF-P5Q.dioxane crystal possesses a macroscopic polarization axis giving rise to ferroelectricity at room temperature. The CT complex manifests ferroelectric features such as optical polarization rotation, temperature-dependent phase transition and piezoelectric response in single crystals. Ferroelectric behavior observed in P5Q-based CT complex widens the scope for further work on this structurally intriguing and readily accessible cyclic pentaquinone.

Cascade energy transfer and tunable emission from nanosheet hybrids: locating acceptor molecules through chiral doping

A donor–acceptor–donor triad with excellent intramolecular energy transfer (99%) exhibits cascade energy transfer in the presence of second acceptors leading to tunable emission colours. Chiral acceptor doping enables chiral induction and to locate acceptors in the donor scaffold.

Counteranion Driven Homochiral Assembly of a Cationic C3-Symmetric Gelator through Ion-Pair Assisted Hydrogen Bond

The helical handedness in achiral self-assemblies is mostly complex due to spontaneous symmetry breaking or kinetically controlled random assembly formation. Here an attempt has been made to address this issue through chiral anion exchange. A new class of cationic achiral C3-symmetric gelator devoid of any conventional gelation assisting functional units is found to form both right- and left-handed helical structures. A chiral counteranion exchange-assisted approach is successfully introduced to control the chirality sign and thereby to obtain preferred homochiral assemblies. Formation of anion-assisted chiral assembly was confirmed by circular dichroism (CD) spectroscopy, microscopic images, and crystal structure. The X-ray crystal structure reveals the construction of helical assemblies with opposite handedness for (+)- and (-)-chiral anion reformed gelators. The appropriate counteranion driven ion-pair-assisted hydrogen-bonding interactions are found responsible for the helical bias control in this C3-symmetric gelator.

Hydrogel-Derived Soft Materials for Biomimetic and Energy-Related Functions

Supramolecular assembly of molecules leading to gelation of large amount of solvents is always a fascinating topic of research. In the very recent past, the exciting developments have marked hydrogels as intriguing materials with excellent features. Hydrogel scaffolds enable the accommodation of organic and/or inorganic guest materials to deliver diverse applications. Hydrogels have been exploited to generate soft materials with mechanical anisotropy, tunable rigidity, self-healing properties, as well as photocatalytic capabilities towards H2 production. Remarkably, the combination of a photocatalyst and a light-harvesting system in the gel matrix provides a unique means to photocatalytic H2 production. The biomimetic applications of hydrogels have also generated much attraction due to their potential demonstrations. The diverse applications underline the significance of such a soft gel medium to reach the final goal. Herein, important reports pertaining to the use of hydrogels as an effective way to generate advanced materials for biomimetic and energy-related issues are discussed.

Self-assembled vesicles of urea-tethered foldamers as hydrophobic drug carriers

Nonamphiphilic α,β-hybrid foldamers form hollow vesicular architectures which can take up and release the anticancer hydrophobic drug curcumin.

Seeded on-surface supramolecular growth for large area conductive donor–acceptor assembly

A seeded, on-surface, supramolecular growth leads to large area conductive donor–acceptor assembly via evaporation-assisted growth from active termini of solution-formed sheaf-like seeds.

Paradigms shift when solvent-less fluids come into play

A new phase of material that challenges the established paradigms.

Nonvolatile liquid anthracenes for facile full-colour luminescence tuning at single blue-light excitation

Nonvolatile room-temperature luminescent molecular liquids are a new generation of organic soft materials. They possess high stability, versatile optical properties, solvent-free fluid behaviour and can effectively accommodate dopant dye molecules. Here we introduce an approach to optimize anthracene-based liquid materials, focussing on enhanced stability, fluorescence quantum yield, colour tunability and processability, with a view to flexible electronic applications. Enveloping the anthracene core in low-viscosity branched aliphatic chains results in stable, nonvolatile, emissive liquid materials. Up to 96% efficient energy-transfer-assisted tunable emission is achieved by doping a minute amount of acceptor dye in the solvent-free state. Furthermore, we use a thermoresponsive dopant to impart thermally controllable luminescence colours. The introduced strategy leading to diverse luminescence colours at a single blue-light excitation can be an innovative replacement for currently used luminescent materials, providing useful continuous emissive layers in developing foldable devices.

Elastic constants of Ultrasonic Additive Manufactured Al 3003-H18

Ultrasonic Additive Manufacturing (UAM), also known as Ultrasonic Consolidation (UC), is a layered manufacturing process in which thin metal foils are ultrasonically bonded to a previously bonded foil substrate to create a net part. Optimization of process variables (amplitude, normal load and velocity) is done to minimize voids along the bonded interfaces. This work pertains to the evaluation of bonds in UAM builds through ultrasonic testing of a build's elastic constants. Results from ultrasonic testing on UAM parts indicate orthotropic material symmetry and a reduction of up to 48% in elastic constant values compared to a control sample. The reduction in elastic constant values is attributed to interfacial voids. In addition, the elastic constants in the plane of the Al foils have nearly the same value, while the constants normal to the foil direction have much different values. In contrast, measurements from builds made with Very High Power Ultrasonic Additive Manufacturing (VHP UAM) show a drastic improvement in elastic properties, approaching values similar to that of bulk aluminum.

Solvent-free luminescent organic liquids

Illuminating! Isolation of a π-core by covalently attached flexible hydrocarbon chains has been employed to synthesize blue-emitting oligo(p-phenylenevinylene) (OPV) liquids with tunable viscosity and optical properties. A solvent-free, stable, white-light emitting ink/paint, which can be applied onto various surfaces and even onto LEDs, was made by blending of liquid OPVs with emissive solid dopants.

Self-assembled gelators for organic electronics

Nature excels at engineering materials by using the principles of chemical synthesis and molecular self-assembly with the help of noncovalent forces. Learning from these phenomena, scientists have been able to create a variety of self-assembled artificial materials of different size, shapes, and properties for wide ranging applications. An area of great interest in this regard is solvent-assisted gel formation with functional organic molecules, thus leading to one-dimensional fibers. Such fibers have improved electronic properties and are potential soft materials for organic electronic devices, particularly in bulk heterojunction solar cells. Described herein is how molecular self-assembly, which was originally proposed as a simple laboratory curiosity, has helped the evolution of a variety of soft functional materials useful for advanced electronic devices such as organic field-effect transistors and organic solar cells. Highlights on some of the recent developments are discussed.