01944nas a2200241 4500008004100000022001400041245007900055210006900134260000800203300001400211490000700225520118000232100001801412700001701430700002401447700002201471700002101493700002201514700002001536700001801556700001901574856010901593 2019 eng d a1528-748300aCrystalline acylhydrazone photoswitches with multiple mechanical responses0 aCrystalline acylhydrazone photoswitches with multiple mechanical cMAY a3039-30440 v193 a

The advancement of our understanding of stimuli responsive molecular crystals has led to the realization that they hold great yet unexplored potential as adaptive materials. Although molecular crystals that exhibit a single mechanical response to a single input stimulus are now abundant, crystals that are capable of response to multiple stimuli are rather scarce. Here we report two photoswitchable acylhydrazone derivatives, Ac-1 and Ac-2, which respond to light as well as to mechanical force. Upon application of localized mechanical stress, the anhydrous (Ac-1a) and monohydrate (Ac-1h) crystals of Ac-1 undergo plastic shearing deformation and bending, whereas monohydrate crystals of Ac-2 undergo elastic deformation. When they are exposed to UV light, crystals of Ac-1h and Ac-2 undergo photoinduced bending; on the other hand, crystals of Ac-1a and thicker crystals of Ac-2 exhibit photosalient effect (light-induced leaping). It is demonstrated that the synergistic action of multiple stimuli (UV light and force) elicits enhanced mechanical response, and this strategy could be employed in the future to increase the efficacy of single crystal actuators.

1 aGupta, Poonam1 aPanda, Tamas1 aAllu, Suryanarayana1 aBorah, Silpisikha1 aBaishya, Anamika1 aGunnam, Anilkumar1 aNangia, Ashwini1 aNaumov, Pance1 aNath, Naba, K. uhttps://library.ncl.res.in/content/crystalline-acylhydrazone-photoswitches-multiple-mechanical-responses02389nas a2200265 4500008004100000022001400041245006000055210005900115260000800174300001200182490000700194520158300201653001901784653002801803653003301831653002301864653001101887100002701898700002401925700001801949700002401967700001901991700002402010856008902034 2023 eng d a1060-132500aEmerging trends in olefin polymerization: a perspective0 aEmerging trends in olefin polymerization a perspective cNOV a731-7500 v603 a

The seemingly matured field of olefin polymerization still poses several challenges and holds enormous potential to meet contemporary material requirements. In this feature article, we examine the progress of olefin polymerization in the last two decades. Among the several emerging trends, we identify four most impactful discoveries, namely, (i) disentangled ultra-high molecular weight polyethylene (dUHMWPE), (ii) disubstituted functional olefin copolymerization, (iii) incorporation of bioderived comonomers in polyolefins, and (iv) application of above (ii, iii) functional polyolefins as compatibilizers. The dUHMWPE has attracted significant attention and heterogeneous Ziegler-type catalysts, homogenous metallocene, and post-metallocene catalysts have been reported to produce disentangled ultrahigh molecular weight polyethylene. Insertion copolymerization of difunctional disubstituted olefins has been reported only recently and ortho-phosphinobenzene sulfonate palladium catalyst outperforms the other catalysts. Interestingly, insertion copolymerization of bioderived olefins has witnessed a surge in the number of reports. Sugar and plant oil-derived olefins have been copolymerized with ethylene to obtain relatively hydrophilic polyethylene. The functional polyethylene is finding a new application as compatibilizer or displays better adhesion to surfaces. Thus, the feature article offers a succinct account of emerging trends in polyolefins, identifies the most impactful contributions, and debates the application potential of these new materials.

10acompatibilizer10aFunctional polyethylene10aInsertion (co)polymerization10arenewable monomers10auHMWPE1 aBirajdar, Rajkumar, S.1 aBodkhe, Dnyaneshwar1 aGupta, Poonam1 aShaikh, Maulali, H.1 aRamekar, Rohan1 aChikkali, Samir, H. uhttps://library.ncl.res.in/content/emerging-trends-olefin-polymerization-perspective02140nas a2200181 4500008004100000022001400041245009300055210006900148260000900217300001000226490000700236520150100243100002701744700001801771700002401789700002401813856012101837 2024 eng d a0020-166900aSynthesis of imine-phenoxy ligated palladium complexes for norbornene homopolymerization0 aSynthesis of iminephenoxy ligated palladium complexes for norbor cDEC  a25-360 v643 a

Metal complexes with tunable ligands play a crucial role in olefin polymerization and impart control over molecular weight, crystallinity, and stereoregularity. We report the single-step synthesis of imine-phenoxy ligands in excellent yields (81-93%). The identity of electronically tuned imine-phenoxy ligands was unambiguously ascertained by using a combination of spectroscopic and analytical methods. These ligands were treated with [Pd(COD)MeCl] in the presence of 2,6-lutidine, resulting in the formation of discrete mononuclear palladium complexes Pd1-Pd4 in excellent yields. 1-2D NMR spectroscopy, mass spectrometry analysis, and single-crystal X-ray diffraction confirmed the identity of the palladium complexes. X-ray analysis revealed a distorted square planar geometry around the palladium center. Proton NMR analysis suggested that the Pd1 catalyst was deshielded, indicating electronically deficient palladium metal compared to the other complexes. Moreover, the Pd1 catalyst showed the highest buried volume percentage (%Vbur = 44.9). When exposed to norbornene, Pd1-Pd4 were found to be active and produced poly(norbornene) (PNB). High-temperature SEC analysis revealed that the electronically deficient and sterically hindered Pd1 catalyst produced the highest molecular weight polymer (PNB 37.4 kDa). Boron and aluminum-based cocatalysts were screened, and MMAO was found to outperform others with high catalytic activity (up to 63.2 x 105 g of PNB (mol Pd)-1 h-1).

1 aBirajdar, Rajkumar, S.1 aGupta, Poonam1 aGonnade, Rajesh, G.1 aChikkali, Samir, H. uhttps://library.ncl.res.in/content/synthesis-imine-phenoxy-ligated-palladium-complexes-norbornene-homopolymerization02521nas a2200265 4500008004100000022001400041245007300055210006900128260000800197300001400205490000600219520170800225653000901933653002001942653001801962653001701980653001901997100001802016700002002034700001802054700002702072700002402099700002702123856010502150 2025 eng d a2637-610500aThermal properties of polyethylene-grafted sheetlike silsesquioxanes0 aThermal properties of polyethylenegrafted sheetlike silsesquioxa cMAR a4290-43000 v73 a

Polyethylene-grafted layered silsesquioxanes, termed polyethylene-clays (PEC), are nanocomposites comprising polyethylene chains tethered to inorganic sheets with a phyllosilicate-like structure. Here, we report that these nanocomposites show two-stage crystallization on cooling, qualitatively different from previous reports on polyethylene nanocomposites. We employ differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) to study the melting and crystallization of PEC. End tethering of the polyethylene chains to a nanosheet strongly influences the manner in which PEC crystallizes from the melt on cooling. PEC exhibits two-step crystallization, characterized by a sharp high-temperature exotherm, followed by a broader exotherm at lower temperatures, in contrast to a single sharp exotherm for neat polyethylene. SAXS indicates that lamellar stacks form at high temperatures and that the low-temperature exotherm corresponds to the formation of additional lamellae and their insertion within these stacks. PEC exhibits lower peak melting temperature, lower crystallinity, and a wider melting range relative to polyethylene. We show that the progress of crystallization of PEC is determined by its ultraslow relaxation dynamics. In contrast, PEC in xylene solution exhibits a significantly shorter relaxation time than the melt PEC. Such systems exhibited a single exotherm on cooling and SAXS structure factor peaks with peak positions in a ratio of 1:2. We hypothesize that the high melt viscosity inhibits the crystallization-induced decrease in the specific volume of PEC, resulting in tensile internal stresses that determine the observed thermal behavior.

10aclay10aCrystallization10aNanocomposite10aPolyethylene10asilsesquioxane1 aSharma, Vivek1 aPaulbudhe, Uday1 aGupta, Poonam1 aZalte, Akshat, Shirish1 aChikkali, Samir, H.1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/thermal-properties-polyethylene-grafted-sheetlike-silsesquioxanes