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Four-dimensional printing refers to a process through which a 3D printed object transforms from one structure into another through the influence of an external energy input. Self-folding structures have been extensively studied to advance 3D printing technology into 4D using stimuli-responsive polymers. Designing and applying self-folding structures requires an understanding of the material properties so that the structural designs can be tailored to the targeted applications. Poly(N-iso-propylacrylamide) (PNIPAM) was used as the thermo-responsive material in this study to 3D print hydrogel samples that can bend or fold with temperature changes. A double-layer printed structure, with PNIPAM as the self-folding layer and polyethylene glycol (PEG) as the supporting layer, provided the mechanical robustness and overall flexibility to accommodate geometric changes. The mechanical properties of the multi-material 3D printing were tested to confirm the contribution of the PEG support to the double-layer system. The desired folding of the structures, as a response to temperature changes, was obtained by adding kirigami-inspired cuts to the design. An excellent shape-shifting capability was obtained by tuning the design. The experimental observations were supported by COMSOL Multiphysics® software simulations, predicting the control over the folding of the double-layer systems. [ABSTRACT FROM AUTHOR]

Three ureido-pyrimidone derivatives (N-L H ) were used to generate in combination with four dinuclear arene ruthenium clips, ( p -cymene) 2 Ru 2 (OO∩OO)Cl 2 (OO∩OO = oxalato, 2,5-dioxido-1,4-benzoquinonato, 2,5-dichloro-1,4-benzoquinonato, 5,8-dioxido-1,4-naphtoquinonato), twelve cationic arene ruthenium metalla-cycles of the general formula [( p -cymene) 2 Ru 2 (OO∩OO)(N-L H ) 2 ] 2 (CF 3 SO 3 ) 4 . The ureido-pyrimidone moieties are able to form strong hydrogen-bonds by self-pairing, thus giving rise to dimeric structures in solution. In addition, to better understand the behavior of the tetranuclear metalla-cycles in solution, the neutral dinuclear arene ruthenium ureido-pyrimidone complexes of the general formula {( p -cymene)RuCl 2 (N-L H )} 2 were also prepared and characterized. All metalla-assemblies were studied in solution by NMR spectroscopy, confirming the high stability of the metalla-cycles and the usefulness of hydrogen-bonds in constructing supramolecular assemblies. [ABSTRACT FROM AUTHOR]

The hydrogen-bonded arene ruthenium metalla-rectangle, [(p-cymene)2Ru2(OO⌒OO)(UPy)2]24+, obtained from 1-(4-oxo-6-undecyl-1,4-dihydropyrimidin-2-yl)-3-(pyridin-4-ylmethyl)urea (UPy) and the dinuclear arene ruthenium clip (p-cymene)2Ru2(OO⌒OO)Cl2 (OO⌒OO = 2,5-dioxido-1,4-benzoquinonato), is investigated by means of solution-phase NMR spectroscopy. Rotating frame nuclear Overhauser effect measurements are used to probe the H-bond network that drives the UPy self-assembly as well as the full rectangular supramolecular system. An effective distance that takes into account both intra- and intermolecular polarization-transfer pathways is utilised for data analysis. The experimental findings are corroborated by DFT calculations of NMR parameters and internuclear distances, thus confirming the formation of a very stable tetranuclear metalla-assembly. [ABSTRACT FROM AUTHOR]

The bis(pyrazole)zinc(II) benzoate complexes bis(3,5-diphenylpyrazole)zinc(II) benzoate (1), bis(3,5-diphenylpyrazole)zinc(II) 3,5-dinitrobenzoate (2), bis(3,5-diphenylpyrazole)zinc(II) 4-hydroxybenzoate (3), and bis(3,5-di-tert-butylpyrazole)zinc(II) 2-chlorobenzoate (4) were synthesized from the reaction of 3,5-diphenylpyrazole (L1) or 3,5-di-tert-butylpyrazole (L2), zinc(II) acetate and the appropriate benzene carboxylic acid. The molecular structure of complex 2 confirmed that these zinc(II) benzoate complexes adopt a 4-coordinate tetrahedral geometry. All four complexes were screened as catalysts for the copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) and were found to be active for the formation of poly(cyclohexene carbonate) (PCHC) at CO2 pressures as low as 1.0 MPa under solvent-free conditions and without the use of a co-catalyst. At some reaction condition, most of the catalysts produced PCHC with high carbonate content of up to 98% and a good amount of cyclic cyclohexene carbonate (CCHC). The copolymers produced have low to moderate molecular weights (5200-12300 g/mol) and with polydispersity indices that vary from 1.19 to 2.50. Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectra (MALDI-TOF MS) of these copolymers showed they have benzoate and hydroxyl end groups. [ABSTRACT FROM AUTHOR]

Nanostructured materials have enabled new ways of controlling the light–matter interaction, opening new routes for exciting applications, in display technologies and colorimetric sensing, among others. In particular, metallic nanoparticles permit the production of color structures out of colorless materials. These plasmonic structural colors are sensitive to the environment and thus offer an interesting platform for sensing. Here, a self‐assembly of aluminum nanoparticles in close proximity of a mirror is spaced by an ultrathin poly(N‐isopropylacrylamide) (PNIPAM) layer. Hybridizing the plasmonic system with the active polymer layer, a thermoresponsive gap‐plasmon architecture is formed that transduces changes in the temperature and relative humidity of the environment into color changes. By harnessing the environmentally induced structural changes of PNIPAM, it was estimated from the finite difference time domain simulation that the resonance can be tuned 7 nm per every 1 nm change in thickness, resulting in color variation. Importantly, these fully reversible changes can be used for reusable powerless humidity and temperature colorimetric sensing. Crucially if condensation on the structure happens, the polymer layer is deformed beyond recovery and the colors are washed away. We leverage this effect to produce tamper‐proof dew labels that a straightforward smartphone app can read by taking a picture. [ABSTRACT FROM AUTHOR]

Abstract: 3,5-Dimethylpyrazole (L), reacts with [Cu(OAc)2] or [Zn(OAc)2]; and either C6H5COOH, 4-OH–C6H5COOH, 3,5-NO2–C6H5COOH or 2-Cl–C6H5COOH to afford the corresponding metal complexes: [Cu(C6H5COO)2(L)2] (1), [Cu(2-Cl–C6H4COO)2(L)2] (2), [Cu(3,5-NO2–C6H3COO)2(L)2] (3), [Cu(4-OH–C6H4COO)2(L)2] (4), [Zn(C6H5COO)2(L)2] (5), [Zn(2-Cl–C6H4COO)2(L)2] (6), [Zn(3,5-NO2–C6H3COO)2(L)2] (7), [Zn(4-OH–C6H4COO)2(L)2] (8). The diamagnetic zinc complexes were characterized by IR, NMR spectroscopy and elemental analysis; while the paramagnetic copper complexes were only characterized by IR spectroscopy, elemental analysis and 1 and 2 were further characterized by single crystal X-ray diffraction studies. All eight complexes are very good initiators for the ring opening polymerization (ROP) of ε-caprolactone and d,l-lactide at elevated temperatures, under solvent-free conditions and in toluene respectively; producing polycaprolactone (PCL) and poly(d,l-lactide) (PLA) of moderate molecular weights (ca 4757Da for PCL and 2484Da for PLA) and narrow polydispersity indices (1.36 for PCL and 1.42 for PLA). The 13C{1H} NMR spectra indicate the stereochemistry of PLA is heterotactic. [Copyright &y& Elsevier]

Active metamaterials, humidity measurements, nanosensors, PNIPAM, self-assembled, structural color Keywords: active metamaterials; humidity measurements; nanosensors; PNIPAM; self-assembled; structural color EN active metamaterials humidity measurements nanosensors PNIPAM self-assembled structural color 1 1 1 08/24/23 20230815 NES 230815 In article number 2300300, Debachis Chanda and co-workers show that integration of an ultrathin layer of poly(N-isopropylacrylamide) (PNIPAM) onto a self-assembled aluminum nanostructure results in the production of a tunable thermoresponsive gap-plasmon that can transduce environmental changes in temperature and humidity into color variation via the deformation of the polymer. This new composite material can function as a fully-reusable, battery-less sensor, as well as a tamper-proof dew label that can be conveniently read through a simple smartphone application. [Extracted from the article]

A high-yield, solvent-free approach to the synthesis of 1,3,5-trisubstituted pyrazoles is reported. Four compounds, (3,5-di-tert-butyl-1H-pyrazole, (2-(3,5-dimethyl-1H-pyrazol-1-yl)ethanol, 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethanol, 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethanol were readily prepared by solvent-free condensation of the appropriate diketone and the respective hydrazine. The crystal structures of the three pyrazolyl-ethanols are typical of N-substituted pyrazoles. All three pyrazolyl compounds show interesting inter-molecular hydrogen bonding. For the 3,5-dimethyl compound the molecules form discrete hydrogen bonded dimers within a unit cell, while for the others the hydrogen bonding is in a head-to-tail arrangement resulting in the formation of chains. [ABSTRACT FROM AUTHOR]

The title compounds (III) and (IV) are readily obtained by solvent-free condensation of the appropriate diketone and hydrazine derivatives. [ABSTRACT FROM AUTHOR]