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This communication introduces helical polyacetylene (P1) with an appended acceptor (A)–donor (D)–acceptor (A) conjugated chromophore as a promising ferroelectric candidate. The helical conformation of P1 leads to a highly stable chiral assembly of the appended ADA chromophores. This results in prominent ferroelectricity as evident from the superior hysteresis loop at room temperature, exhibiting a saturation polarization (PS) value ∼2 μC cm−2 and remanent polarization (Pr) value ∼1.8 μC cm−2 at a low coercive field (Ec) of 5.2 kV cm−1, rarely reported before for purely organic systems. [ABSTRACT FROM AUTHOR]

Organic ferroelectric (FE) materials, though known for more than a century, are yet to reach close to the benchmark of inorganic or hybrid materials in terms of the magnitude of polarization. Amongst the different classes of organic systems, donor (D)–acceptor (A) charge‐transfer (CT) complexes are recognized as promising for ferroelectricity owing to their neutral‐to‐ionic phase transition at low temperature. This review presents an overview of different supramolecular D‐A systems that have been explored for FE phase transitions. The discussion begins with a general introduction of ferroelectricity and its different associated parameters. Then it moves on to show early examples of CT cocrystals that have shown FE properties at sub‐ambient temperature. Subsequently, recent developments in the field of room temperature (RT) ferroelectricity, exhibited by H‐bond‐stabilized lock‐arm supramolecular‐ordering (LASO) in D‐A co‐crystals or other FE CT‐crystals devoid of neutral‐ionic phase transition are discussed. Then the discussion moves on to emerging reports on other D‐A soft materials such as gel and foldable polymers; finally it shows very recent developments in ferroelectricity in supramolecular assemblies of single‐component dipolar or ambipolar π‐systems, exhibiting intra‐molecular charge transfer. The effects of structural nuances such as H‐bonding, balanced charge transfer and chirality on the observed ferroelectricity is described with the available examples. Finally, piezoelectricity in recently reported ambipolar ADA‐type systems are discussed to highlight the future potential of these soft materials in micropower energy harvesting. [ABSTRACT FROM AUTHOR]

Aggregation of amphiphilic polymers in block-selective solvents produces different nanostructures, which have been studied extensively for wide-ranging applications. Nevertheless, such immiscibility-driven aggregation does not endow them with the desired structural precision, predictability or surface functional group exposure, which significantly impact their functional applications. More recently, biomimetic folded structures of synthetic macromolecules (mostly oligomers) have come to the fore, but such studies have been limited to probe the secondary structures. In this article, we have collated hierarchical structures of foldamers, especially highlighting our recent contribution to the field of chain-folding regulated assembly of segmented polyurethanes (PUs) and their functional applications. A series of such PUs have been discussed, which contain a segmented hydrocarbon backbone and alternately placed pendant solvophilic groups. In either water or highly non-polar solvents (TCE, MCH), depending on the nature of the pendant group, they exhibit folded structures stabilized by intra-chain H-bonding. Hierarchical assembly of such folded chains by inter-chain H-bonding and/or π-stacking leads to the formation of well-defined nanostructures with functional applications ranging from organic optoelectronics to biomaterials. For example, a segmented PU with appended naphthalene-diimide (NDI) chromophores showed a pleated structure in MCH, which helped in organization of the NDI chromophores within π-stacking distance. Such folded polymer chains eventually produced nanotubular structures with excellent electron mobility. They also showed efficient intercalation of the pyrene (Py) donor by NDI–Py charge-transfer interaction and in this case the mixed nanotubular structure exhibited prominent room-temperature ferroelectricity. On the other hand, having cationic functionalities as the pendant groups such chain-folding regulated assembly produced unilamellar polymersomes with excellent antibacterial activity with very low minimum inhibitory concentrations (<10 μg mL−1). Replacing the pendant amine functionality with sulphate groups made these polyurethanes highly potent antiviral materials. In the absence of the alternating connectivity of the solvophobic and solvophilic segments or rigid hydrocarbon backbone, such folding propensity is destroyed, leading to structural collapse. While significant efforts have been made in correlating primary structures of wide-ranging polymers with their functional applications, this article demonstrates the direct correlation between the secondary structures of polymers and their functional properties. [ABSTRACT FROM AUTHOR]

Determination of the critical micelle concentration (CMC) of several surfactants that contain an NLO chromophore, either at the hydrocarbon tail, or at the hydrophilic headgroup, or even as a counterion, was done by hyper-Rayleigh scattering (HRS). The CMC is detected by an unprecedented drop in the HRS signal, which is believed to be due to the formation of smaller pre-micellar aggregates whose effective beta value is higher than that of the micellar aggregates.

1H NMR titration of 9-N-butyladenine (1) with a series of 11 representative carboxylic acids was conducted in CDCl3 by following the chemical shifts of delta(sub H-2) and delta(sub H-8) of 1 to obtain the association constants for the Watson-crick and the Hoogsteen modes of binding. Compound 1 was found to bind carboxylic acids through the Watson-Crick (WC) site or the Hoogsteen (HG) site. The binding of the carboxylic acids from WC site shifts the delta(sub H-2) signal upfield, while the binding from the HG site shifts the delta(sub H-8) signal downfield.

Organic thermoelectric materials (OTEs) are in huge demand for their flexibility and robustness in applications of internet‐of‐things, wearables, and health monitoring devices. While choices of p‐type OTEs are widespread, there is still lack of stable (in air) n‐type systems to pair. Naphthalene‐diimides (NDIs), due to the presence of the planar‐structured electron‐deficient aromatic ring offer promising electron‐deficient building blocks to construct air‐stable n‐type semiconducting devices. Herein, an amphiphile derivative (cNDI‐1) is reported for two‐dimensional supramolecular assembly, and consequently TE measurements are carried out in a fully calibrated and standardised custom‐built Seebeck (S) set‐up. Promising S values (ca. −237 μV/K in THF and ca. −195 μV/K in water) are measured with a TE power factor of ∼0.05×10−5 μW/mK2 in THF and ∼0.6×10−5 μW/mK2 in water at room temperature. The study opens up the possibility of exploring broad range of molecular design library for newer n‐type OTEs. [ABSTRACT FROM AUTHOR]