@article {46118, title = {Crystalline acylhydrazone photoswitches with multiple mechanical responses}, journal = {Crystal Growth \& Design}, volume = {19}, year = {2019}, month = {MAY}, pages = {3039-3044}, type = {Article}, abstract = {

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.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.8b01860}, author = {Gupta, Poonam and Panda, Tamas and Allu, Suryanarayana and Borah, Silpisikha and Baishya, Anamika and Gunnam, Anilkumar and Nangia, Ashwini and Naumov, Pance and Nath, Naba K.} } @article {48942, title = {Emerging trends in olefin polymerization: a perspective}, journal = {Journal of macromolecular science part A- pure and applied chemistry }, volume = {60}, year = {2023}, month = {NOV}, pages = {731-750}, type = {Article}, abstract = {

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.

}, keywords = {compatibilizer, Functional polyethylene, Insertion (co)polymerization, renewable monomers, uHMWPE}, issn = {1060-1325}, doi = {10.1080/10601325.2023.2269971}, author = {Birajdar, Rajkumar S. and Bodkhe, Dnyaneshwar and Gupta, Poonam and Shaikh, Maulali H. and Ramekar, Rohan and Chikkali, Samir H.} } @article {49563, title = {Thermal properties of polyethylene-grafted sheetlike silsesquioxanes}, journal = {ACS Applied Polymer Materials}, volume = {7}, year = {2025}, month = {MAR}, pages = {4290-4300}, type = {Article}, abstract = {

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.

}, keywords = {clay, Crystallization, Nanocomposite, Polyethylene, silsesquioxane}, issn = {2637-6105}, doi = {10.1021/acsapm.4c04181}, author = {Sharma, Vivek and Paulbudhe, Uday and Gupta, Poonam and Zalte, Akshat Shirish and Chikkali, Samir H. and Kumaraswamy, Guruswamy} }