Aminoxyl Radicals from N-Phenyl-1-(2-oxo-1-azacycloalkyl)-methanesulfonamides

Summary. The synthesis and reaction with two oxidation agents is described for N-phenyl-1-(2-oxo-1-azacycloalkyl)methanesulfonamides. Their oxidation was carried out using radicals and 3-chloroperbenzoic acid. In both cases, the EPR spectra of corresponding aminoxyl radicals were recorded. Their simulation confirmed that the –SO₂– group in the neighbourhood of the – – fragment does not prevent the interaction of the unpaired electron with the methylene protons and the nitrogen atom of the heterocyclic ring.     

Elastic piezoelectric aerogels from isotropic and directionally ice-templated cellulose nanocrystals: comparison of structure and energy harvesting

We report the preparation of highly compressible and elastic piezoelectric aerogels of carboxylated cellulose nanocrystals (CNCs). Aqueous CNC dispersions containing polyethyleneimine and crosslinker were frozen isotropically to yield isotropic aerogels, while oriented aerogels were prepared by directional freezing. These aerogels were highly flexible and porous (~?85% void fraction), exhibiting greater than 90% recovery at 50% compressive strain even after 100 compression–decompression cycles. Since such aerogels with low bulk modulus and high anisotropy would be an ideal platform for leveraging the piezoelectric properties of CNCs, we used them to prepare piezoelectric nanogenerator devices and determined their energy transduction behavior. Anisotropic aerogels led to an enhanced open-circuit voltage of 840 mV (at ~?8 N applied force), which is over 2.6 times higher than isotropic aerogels (320 mV). The energy density of anisotropic aerogels was around 52 nW/cm², representing outstanding piezoelectric performance for cellulose-based aerogels. Such aerogels with high compressibility, elastic recovery and exceptional piezoelectric performance could have potential applications in sensors, wearable electronics, etc.

     

Piezoelectric Energy Harvesting from a Ferroelectric Hybrid Salt [Ph3MeP]4[Ni(NCS)6] Embedded in a Polymer Matrix

Organic–inorganic hybrid ferroelectrics are an exciting class of molecular materials with promising applications in the area of energy and electronics. The synthesis, ferroelectric and piezoelectric energy harvesting behavior of a 3d metal ion‐containing A₄BX₆ type organic–inorganic hybrid salt [Ph₃MeP]₄[Ni(NCS)₆] ( 1 ) is now presented. P‐E hysteresis loop studies on 1 show a remnant ferroelectric polarization value of 18.71 μC cm^?2, at room temperature. Composite thermoplastic polyurethane (TPU) devices with 5, 10, 15 and 20 wt % compositions of 1 were prepared and employed for piezoelectric energy harvesting studies. A maximum output voltage of 19.29 V and a calculated power density value of 2.51 mW cm^?3 were observed for the 15 wt % 1 ‐TPU device. The capacitor charging experiments on the 15 wt % 1 ‐TPU composite device shows an excellent energy storage performance with the highest stored energies and measured charges of 198.8 μJ and 600 μC, respectively.     

A Flexible Composite Mechanical Energy Harvester from a Ferroelectric Organoamino Phosphonium Salt

A new binary organic salt diphenyl diisopropylamino phosphonium hexaflurophosphate (DPDP?PF₆) was shown to exhibit a good ferroelectric response and employed for mechanical energy harvesting application. The phosphonium salt crystallizes in the monoclinic noncentrosymmetric space group Cc and exhibits an H‐bonded 1D chain structure due to N?H???F interactions. Ferroelectric measurements on the single crystals of DPDP?PF₆ gave a well‐saturated rectangular hysteresis loop with a remnant (P_r) polarization value of 6 μC cm^?2. Further, composite devices based on polydimethylsiloxane (PDMS) films for various weight percentages (3, 5, 7, 10 and 20 wt %) of DPDP?PF₆ were prepared and examined for power generation by using an impact test setup. A maximum output peak‐to‐peak voltage (V_PP) of 8.5 V and an output peak‐to‐peak current (I_PP) of 0.5 μA was obtained for the non‐poled composite film with 10 wt % of DPDP?PF₆. These results show the efficacy of organic ferroelectric substances as potential micropower generators.     

Aminoxyl Radicals from N-Phenyl-1-(2-oxo-1-azacycloalkyl)-methanesulfonamides

The synthesis and reaction with two oxidation agents is described for N-phenyl-1-(2-oxo-1-azacycloalkyl)methanesulfonamides. Their oxidation was carried out using RO_2^·R{\rm O}_{2^\bullet} radicals and 3-chloroperbenzoic acid. In both cases, the EPR spectra of corresponding aminoxyl radicals were recorded. Their simulation confirmed that the –SO₂– group in the neighbourhood of the – NO^·{{\rm NO}^\bullet} – fragment does not prevent the interaction of the unpaired electron with the methylene protons and the nitrogen atom of the heterocyclic ring.