Nowadays, the chemical industry is looking for sustainable chemicals to synthesize nanocomposite bio-based polyurethane foams, PUs, with the aim to replace the conventional petrochemical precursors. Some possibilities to increase the environmental sustainability in the synthesis of nanocomposite PUs include the use of chemicals and additives derived from renewable sources (such as vegetable oils or biomass wastes), which comprise increasingly wider base raw materials. Generally, sustainable PUs exhibit chemico-physical, mechanical and functional properties, which are not comparable with those of PUs produced from petrochemical precursors. In order to enhance the performances, as well as the bio-based aspect, the addition in the polyurethane formulation of renewable or natural fillers can be considered. Among these, walnut shells and cellulose are very popular wood-based waste, and due to their chemical composition, carbohydrate, protein and/or fatty acid, can be used as reactive fillers in the synthesis of Pus. Diatomite, as a natural inorganic nanoporous filler, can also be evaluated to improve mechanical and thermal insulation properties of rigid PUs. In this respect, sustainable nanocomposite rigid PU foams are synthesized by using a cardanol-based Mannich polyol, MDI (Methylene diphenyl isocyanate) as an isocyanate source, catalysts and surfactant to regulate the polymerization and blowing reactions, H2O as a sustainable blowing agent and a suitable amount (5 wt%) of ultramilled walnut shell, cellulose and diatomite as filler. The effect of these fillers on the chemico-physical, morphological, mechanical and functional performances on PU foams has been analyzed.

This investigation presents a new approach to obtain free-standing thermally-triggered “two-way” shape-memory actuators by realizing multilayer structures constituted by glassy thermoset (GT) films anchored to a previously programmed liquid-crystalline network (LCN) film. The GT is obtained via dual-curing of off-stoichiometric “thiol-epoxy” mixtures, thus enabling the development of complex actuator configurations thanks to the easy processing in the intermediate stage, and a compact and resistant design due to the strong adhesion between the layers obtained upon the final curing stage of the GT. A model based on the classical multilayered beam theory to predict the maximum deflection of a “beam-like” design is proposed and its reliability is verified by experimental investigation of actuators with different configurations and LCN stretching levels. The results show the capability of these actuators to bend and unbend under various consecutive heating–cooling procedures in a controlled way. The maximum deflection can be modulated through the configuration and the LCN stretching level, showing an excellent fitting with the model predictions. The model is able to predict high actuation levels (angles of curvature ˜ 180°) and the bidirectional shape-memory behavior of the device as a function of the thickness, configuration of the layers, and the LCN stretching level. This approach enables the design of free-standing two-way actuators covering a range of bending actuation from 27 to 98% of the theoretical maximum deflection.Postprint (author's final draft

Interaction of nanoparticles (NPs) with cells is of fundamental importance in biology and biomedical sciences. NPs can be taken up by cells, thus interacting with their intracellular elements, modifying the life cycle pathways, and possibly inducing death. Therefore, there is a great interest in understanding and visualizing the process of cellular uptake itself or even secondary effects, for example, toxicity. Nowadays, no method is reported yet in which 3D imaging of NPs distribution can be achieved for suspended cells in flow-cytometry. Here we show that, by means of label-free tomographic flow-cytometry, it is possible to obtain full 3D quantitative spatial distribution of nanographene oxide (nGO) inside each single flowing cell. This can allow the setting of a class of biomarkers that characterize the 3D spatial intracellular deployment of nGO or other NPs clusters, thus opening the route for quantitative descriptions to discover new insights in the realm of NP–cell interactions.

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Humidity-driven and electrically responsive graphene/cloisite hybrid films are obtained by casting water dispersions of graphene oxide and cloisite Na + . Coupling hydrophilicity and a high water vapor barrier in a homogenous film enables to realize humidity-driven actuators which exploit the water gradient generated across the film section under asymmetric exposure to humidity. The hybrid films are self-standing, flexible, and exhibit fast humidity-triggered bidirectional bending up to 75°, which is tuned by varying the relative amount of the two components. Up to 60% of the bending angle can be preserved at the steady state, providing a large and reliable response to humidity. Moreover, thermal treatment results in the reduction of graphene oxide, endowing the films with humidity-dependent electrical conductivity, which increases from 1.5 × 10 −6 S at 20% relative humidity (RH) up to 2.7 × 10 −5 S at 90% RH. The films are used to realize a humiditysensitive electrical switching system in which the reversible actuation is due to water desorption induced by the Joule effect. Due to their ease of preparation and tunable properties, this new class of graphene-based materials is suitable for the realization of humidity-driven and electrically responsive actuators and sensors. development of new humidity-driven mechanically and electrically responsive actuators and sensors.

Graphene family materials (GFMs) have large perspectives for drug-delivery applications, but their internalization in live cells is under investigation in a wide variety of studies in order to assess the best conditions for efficient cellular uptake. Here we show that mild oxidation of graphene nanoplatelets produces nanographene oxide (nGO) particles, which are massively internalized into the cell cytoplasm. This remarkable uptake of nGO in NIH-3T3 cells has never been observed before. We performed vitality tests for demonstrating the biocompatibility of the material and analyzed the internalization mechanism under different oxidation degrees and concentrations. Moreover, we evaluated quantitatively, for the first time, the cell volume variation after nGO internalization in live cells through a label-free digital holographic imaging technique and in quasi-real-time modality, thus avoiding the time-consuming and detrimental procedures usually employed by electron-based microscopy. The results demonstrate that nGO formulations with a tailored balance between the exposed surface and content of functional groups are very promising in drug-delivery applications.

In this paper, epoxy-based shape-memory liquid crystalline lightly cross-linked networks (LCN) are synthesized and characterized with a view to the future development of two-way\ud autonomous shape-memory actuators by coupling the LCN with an external epoxy-matrix. Carboxylic acids of different aliphatic chain lengths are used as curing agents for a rigid-rod epoxy-based mesogen. Thermal and liquid-crystalline (LC) properties of the LCN are investigated through calorimetric and X-ray diffraction analysis on unstretched and stretched samples. Structural and thermomechanical properties are studied by means of tensile and dynamic-mechanical analyses and the shape-memory capabilities are analyzed in terms of\ud actuation strain and stress under partially- and fully constrained thermomechanical procedures. The results have shown the possibility to obtain LCN with isotropization temperatures above 100 °C, controlled degree of liquid crystallinity, and high actuation stress and strain by simply varying the aliphatic chain length of the curing agent. Moreover, by properly adjusting the\ud programming conditions (stress level), it is possible to optimize and stabilize the actuation performance. In addition, the effects of the liquid-crystalline domains on the network relaxation and their degree of orientation after programming at the different stress levels have been discussed. Overall, proper design of chain length and stress level allows strain actuation to be modulated from low, ∼60%, to high, ∼160% strain levels. The results evidence the possibility of finely tuning LCN with controlled and stable actuation protocols by balancing the aliphatic chain length and programming conditions

Thermally induced shape-memory polymers are materials based on\ud exploiting one or more phase transitions, such as glass, melting, or clearing transition,\ud to trigger a shape-memory effect. Among shape-memory polymers, liquid crystalline\ud elastomers are considered as very interesting candidates, thanks to the synergistic\ud effect of the ordered liquid crystalline phase and the polymeric network on their\ud programming and recovering behavior. Here, the synthesis of new shape-memory\ud smectic epoxy-based elastomers incorporating multiwalled carbon nanotubes is\ud reported. The realized materials show two types of shape-memory behavior that can\ud be selectively actuated by choosing the appropriate thermal recovery conditions. The\ud surface modification of the nanotubes enables a dramatic enhancement of the\ud actuation extent at low nanofiller content. Moreover, the stress threshold required to\ud trigger the reversible thermomechanical actuation is significantly decreased. The effect\ud of nanotubes on thermomechanical properties of the materials is elucidated and\ud correlated to the microstructure and phase behavior of the host system. Results demonstrate that the incorporation of\ud multiwalled carbon nanotubes amplifies the soft-elastic response of the liquid crystalline phase to external stimuli. Tunable\ud thermomechanical properties of these systems make them potentially suitable for a variety of applications ranging to robotics,\ud sensing and actuation, and artificial muscles