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Retrieving the starting monomer from polymers synthesized by reversible deactivation radical polymerization has recently emerged as an efficient way to increase the recyclability of such materials and potentially enable their industrial implementation. To date, most methods have primarily focused on utilizing high temperatures (typically from 120 °C to 180 °C) to trigger an efficient depolymerization reaction. In this work, we show that, in the presence of Eosin Y under light irradiation, a much faster depolymerization of polymers made by reversible addition-fragmentation chain-transfer (RAFT) polymerization can be triggered even at a lower temperatures (i.e. 100 °C). For instance, green light, in conjunction with ppm amounts of Eosin Y, resulted in depolymerization acceleration of poly(methyl methacrylate) from 16% (thermal depolymerization at 100°C) to 37% within 1 hour, and a final 80% of depolymerization after 8 hours, as confirmed by both 1H-NMR and SEC analysis. The enhanced depolymerization rate was attributed to the activation of the macroCTA from Eosin Y, thus resulting in a faster macroradical generation. Notably, this method was found to be compatible with different wavelengths (e.g. blue, red and white irradiation), solvents, and RAFT agents, thus highlighting the potential of light to significantly improve current depolymerization approaches., Polymer Chemistry, 14 (3), ISSN:1759-9962, ISSN:1759-9954

The synthesis of hydrogels that are based on poly-hydroxyethyl methacrylate, p(HEMA), network semi-interpenetrated with linear polyvinylpyrrolidone (PVP) was optimized in order to allow both a fast preparation and a high cleaning effectiveness of artistic surfaces. For this purpose, the synthesis parameters of the gel with PVP having a high molecular weight (1300 kDa) that were reported in the literature, were modified in terms of temperature, time, and crosslinker amount. In addition, the gel composition was modified by using PVP with different molecular weights, by changing the initiator and by adding maleic anhydride. The modified gels were characterized in terms of equilibrium water content (EWC), water uptake, conversion grade, and thermal properties by differential scanning calorimetry (DSC). The cleaning effectiveness of the gels was studied through the removal of copper salts from laboratory-stained specimens. Cleaning materials were characterized by electron paramagnetic resonance (EPR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and inductively-coupled plasma-mass spectrometry (ICP-MS). Cleaning was assessed on marble specimens by color variation measurements. The gel synthesis is accelerated by using PVP 360 kDa. The addition of maleic anhydride in the p(HEMA)/PVP network allows the most effective removal of copper salt deposits from marble since it acts as a chelator towards copper ions.

Water-in-salt solutions, i.e. solutions in which the amount of salt by volume or weight is larger than that of the solvent, are attracting increasing attention in electrochemistry due to their distinct features that often include decomposition potentials much higher than those of lower concentration solutions. Despite the high solubility of potassium acetate (KAC) in water at room temperature (up to 25 moles of salt per kg of solvent), the low cost, and the large availability, the use of highly concentrated KAC solutions is still limited to a few examples in energy storage applications and a systematic study of their physical-chemical properties is lacking. To fill this gap, we have investigated the thermal, rheological, electrical, electrochemical, and spectroscopic features of KAC/water solutions in the compositional range between 1 and 25 mol kg-1. We show the presence of a transition between the "salt-in-solvent" and "solvent-in-salt" regimes in the range of 10-15 mol kg-1. Among the explored compositions, the highest concentrations (20 and 25 mol kg-1) exhibit good room temperature conductivity values (55.6 and 31 mS cm-1, respectively) and a large electrochemical potential window (above 2.5 V).

The development of mulch films from wastes of vegetables represents a sustainable alternative to the traditionally used polyethylene ones that follow the principles of circular economy. In this work, we obtained films based on two different industrial vegetable wastes, orange peels (OP) and spinach stems (SS), using hydrolysis at different times (6, 16, and 24 h) and temperatures (30, 50, and 70 °C). Hydrolysis carried out at 30 °C and 24 h has led to films with the best mechanical properties, while high temperatures (70 °C) combined with prolonged treatment times (16 and 24 h) led to materials with lower mechanical resistance and darker coloration. The films' characterization by X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and uniaxial tensile tests elucidated their chemical structure and physicochemical properties. Additionally, the materials' interaction with water was evaluated and significantly improved by adding a carnauba wax coating. Optical properties, micro and macronutrient content and biodegradation in the soil of selected bioplastics were also determined. Results showed that the proposed materials present fast in-soil biodegradation, good potentiality for weed prevention and improvement of plant growth via soil fertilization.

The effectiveness of Agar gels for copper stain removal from marble surfaces was systematically studied. Gels with different agar concentrations (1, 3, 5%) and different chelating agents used as additives (ethylenediaminetetraacetic acid, EDTA, and ammonium citrate tribasic, TAC) were tested on laboratory marble specimens for different contact times (30 and 60 min). For better characterization, hydrogels were lyophilised and cryogels were obtained. Systematic comparison of different formulations was feasible on cryogels and performed in terms of: (i) the morphological properties, by field-emission scanning electron microscopy (FE-SEM); (ii) the type of Cu(II)-complexes formed and their quantitative comparison by electron paramagnetic resonance (EPR) spectroscopy; (iii) the total amount of copper removed from marble surfaces, by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES). AgarArt 1% with TAC exhibited the highest effectiveness for copper stain removal after 60 min contact (431 μg/cm2). Such a good cleaning effectiveness can be ascribed to the co-presence of the following properties: efficient metal coordination, which is related to the additive presence, and favourable gel morphology, related both to the gel concentration and to the additive type. In fact, it was observed that both the low gel concentration and the presence of TAC are related to a narrow pore size distribution in gels, besides the possibility of copper coordination. The presence of EDTA results in a broader pore size distribution and in a lower gel strength, with respect to gels with TAC. Thus, a new procedure for studying gels was proposed, which allows to optimize the conditions for metal stain removal from built heritage.

Porous materials are ubiquitous systems with a large variety of applications from catalysis to polymer science, from soil to life science, from separation to building materials. Many relevant systems of biological or synthetic origin exhibit a hierarchy, defined as spatial organization over several length scales. Their characterization is often elusive, since many techniques can only be employed to probe a single length scale, like the nanometric or the micrometric levels. Moreover, some multiscale systems lack tridimensional order, further reducing the possibilities of investigation. 129Xe nuclear magnetic resonance (NMR) provides a unique and comprehensive description of multiscale porous materials by exploiting the adsorption and diffusion of xenon atoms. NMR parameters like chemical shift, relaxation times, and diffusion coefficient allow the probing of structures from a few angstroms to microns at the same time. Xenon can evaluate the size and shape of a variety of accessible volumes such as pores, layers, and tunnels, and the chemical nature of their surface. The dynamic nature of the probe provides a simultaneous exploration of different scales, informing on complex features such as the relative accessibility of different populations of pores. In this review, the basic principles of this technique will be presented along with some selected applications, focusing on its ability to characterize multiscale materials.

Diels-Alder chemistry has been used for the thermoreversible cross-linking of furan-functionalized ethylene/propylene (EPM) and ethylene/vinyl acetate (EVM) rubbers. Both furan-functionalized elastomers were successfully cross-linked with bismaleimide to yield products with a similar cross-link density. NMR relaxometry and SAXS measurements both show that the apolar EPM-g-furan precursor contains phase-separated polar clusters and that cross-linking with polar bismaleimide occurs in these clusters. The heterogeneously cross-linked network of EPM-g-furan contrasts with the homogeneous network in the polar EVM-g-furan. The heterogeneous character of the cross-links in EPM-g-furan results in a relatively high Youngs modulus, whereas the more uniform cross-linking in EVM-g-furan results in a higher tensile strength and elongation at break.

Lithium Metal Batteries (LMB) require solid or quasi-solid electrolytes able to block dendrites formation during cell cycling. Polymer-in-ceramic nanocomposites with the ceramic fraction exceeding the one normally used as the filler (>10 ÷ 15 wt%) are among the most interesting options on the table. Here, we report on a new hybrid material encompassing brush-like TiO2 nanocrystals functionalized with low molecular weight poly(ethylene oxide) (PEO). The nanocomposite electrolyte membranes are then obtained by blending the brush-like nanocrystals with high molecular weight PEO and LiTFSI. The intrinsic chemical compatibility among the PEO moieties allows a TiO2 content as high as ∼39 wt% (90:10 w/w functionalized nanocrystals/PEO-LiTFSI), while maintaining good processability and mechanical resistance. The 50:50 w/w nanocomposite electrolyte (18.8 wt% functionalized TiO2) displays ionic conductivity of 3 × 10−4 S cm−1 at 70 °C. Stripping/plating experiments show an excellent long-term behavior even at relatively high currents of 200 μA cm−2. Upon testing in a lab-scale Li/electrolyte/LiFePO4 cell, the material delivers 130 mAh g−1 and 120 mAh g−1 after 40 and 50 cycles at 0.05 and 0.1 mA, respectively, with Coulombic efficiency exceeding 99.5%, which demonstrates the very promising prospects of these newly developed nanocomposite solid electrolyte for future development of LMBs.

The possibility to use vegetable biomass, with minimal processing, as new green bioplastic for packaging is very appealing to mitigate environmental issues due to broad usage of conventional plastics. Here we developed vegetable bioplastic films from carrot pomace with good mechanical properties and glass transition temperature function of humidity, with a lowest value of −60 °C when highly hydrated. These properties were exploited to set-up scalable and green fabrication techniques for the production of macroscopic objects with elaborate shapes and detailed features at the micro scale. By means of a combination of techniques (FTIR, NMR, DSC and DMTA) we provide a comprehensive picture of the material structure and how the absorbed water changes the macromolecules’ structure, finally explaining the source of the glass transition of the material.

Subtle alterations in the mid-block of polystyrene-b-poly (ethylene-co-butylene)-b-polystyrene (SEBS) have a significant impact on the mechanical properties of the resulting microphase separated materials. In samples with high butylene content, the ethylene-co-butylene (EB) phase behaves as a rubber, as seen by differential scanning calorimetry (DSC), time domain (TD) and Magic Angle Spinning (MAS) NMR, X-ray scattering at small (SAXS), and wide (WAXS) angles. In samples where the butylene content is lower&mdash, but still sufficient to prevent crystallization in bulk EB&mdash, the DSC thermogram presents a broad endothermic transition upon heating from 221 to 300 K. TD NMR, supported by WAXS and dielectric spectroscopy measurements, probed the dynamic phenomena of EB during this transition. The results suggest the existence of a rotator phase for the EB block below room temperature, as a result of nanoconfinement.

Micro and mesoporous materials are often used in catalysis, purification, composite filler, and other applications. Almond shell is an important agricultural byproduct that can be transformed to microporous and mesoporous carbon. In this work, we produced biochar from almond shell using a thermal treatment procedure in an inert atmosphere and characterized the pores with nitrogen adsorption, environmental SEM, and 129Xe NMR. The latter technique differentiates adsorbed and nonadsorbed xenon and permits the correlation of different processing conditions with xenon adsorption and diffusivity. The relevance of removing the ash produced during the charring process has been included in the study. Moreover, the xenon exchange between meso- and micro-pores has been directly observed by 129Xe NMR, demonstrating that after ash removal by water the materials have high accessibility of the pores by external fluids, thus increasing the usefulness as filtration or adsorption material.

Luminescent solar concentrators serving as semitransparent photovoltaic windows could become an important element in net zero energy consumption buildings of the future. Colloidal quantum dots are promising materials for luminescent solar concentrators as they can be engineered to provide the large Stokes shift necessary for suppressing reabsorption losses in large-area devices. Existing Stokes-shift-engineered quantum dots allow for only partial coverage of the solar spectrum, which limits their light-harvesting ability and leads to colouring of the luminescent solar concentrators, complicating their use in architecture. Here, we use quantum dots of ternary I-III-VI 2 semiconductors to realize the first large-area quantum dot-luminescent solar concentrators free of toxic elements, with reduced reabsorption and extended coverage of the solar spectrum. By incorporating CuInSe x S 2-x quantum dots into photo-polymerized poly(lauryl methacrylate), we obtain freestanding, colourless slabs that introduce no distortion to perceived colours and are thus well suited for the realization of photovoltaic windows. Thanks to the suppressed reabsorption and high emission efficiencies of the quantum dots, we achieve an optical power efficiency of 3.2%. Ultrafast spectroscopy studies suggest that the Stokes-shifted emission involves a conduction-band electron and a hole residing in an intragap state associated with a native defect.

Luminescent solar concentrators are cost-effective complements to semiconductor photovoltaics that can boost the output of solar cells and allow for the integration of photovoltaic-active architectural elements into buildings (for example, photovoltaic windows). Colloidal quantum dots are attractive for use in luminescent solar concentrators, but their small Stokes shift results in reabsorption losses that hinder the realization of large-area devices. Here, we use Stokes-shift-engineeredCdSe/CdS quantum dots with giant shells (giant quantum dots) to realize luminescent solar concentrators without reabsorption losses for device dimensions up to tens of centimetres. Monte-Carlo simulations show a 100-fold increase in efficiency using giant quantum dots compared with core-only nanocrystals. We demonstrate the feasibility of this approach by using high-optical-quality quantum dot-polymethylmethacrylate nanocomposites fabricated using a modified industrial method that preserves the light-emitting properties of giant quantum dots upon incorporation into the polymer. Study of these luminescent solar concentrators yields optical efficiencies >10% and an effective concentration factor of 4.4. These results demonstrate the significant promise of Stokes-shift-engineered quantum dots for large-area luminescent solar concentrators. © 2014 Macmillan Publishers Limited. All rights reserved.

Optically active materials able to up-convert the frequency of the incident radiation can be used to enhance the performance of photovoltaic and photocatalityc cells, recovering sub-bandgap photons not directly absorbed by the devices. Actually, sensitized up-conversion (SUC) based on multi-component organic systems is the most promising approach for these photon energy managing processes, being efficient also at the solar irradiance. However, applications of SUC on real devices have not been yet accomplished because its conversion yield usually drops dramatically in the solid state where the low dye mobility inhibits the diffusion controlled mechanisms ruling SUC photophysics. To overcome this limit, we prepared a single-phase elastomer (poly-butylacrilate) doped with proper dyes (platinum (II) octaetyl-porphyrin and 9,10-diphenylanthracene) to fabricate an efficient photon up-converting material. Thanks to the residual molecular diffusion provided by the soft host, and to the quenching reduction of involved metastable electronic excited-states in a solid environment compared to a liquid one, we obtained a record SUC yield of 17% at the solid state. SUC efficiency has been studied as function of the excitation power and sample temperature, elucidating the photophysical processes at the base of the high observed yield and assessing the guidelines for the fabrication of technologically appealing low power up-converting materials. A dye-doped rubbery matrix of poly-butylacrilate is used to fabricate an efficient photon up-converting material by bulk polymerization. Thanks to the residual molecular diffusion within the host and to the reduction of the vibrational quenching of involved metastable electronic states, a record conversion yield of 17% in the solid state is obtained within a single phase elastomer. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We have investigated several building stone materials, including minerals and rocks, using continuous flow hyperpolarized xenon (CF-HP) NMR spectroscopy to probe the surface composition and porosity. Chemical shift and line width values are consistent with petrographic information. Rare upfield shifts were measured and attributed to the presence of transition metal cations on the surface. The evolution of freshly cleaved rocks exposed to the atmosphere was also characterized. The CF-HP 129Xe NMR technique is non-destructive and it could complement currently used techniques, like porosimetry and microscopy, providing additional information on the chemical nature of the rock surface and its evolution. ©2012 by the authors.

We studied the network structure of elastomers based on polyisoprene, polybutadiene, and their blends in the narrow range of formulations compatible with actual use in the automotive tyre industry. Cross-link density (CLD) was quantified comparatively by low-field 1H multiple quantum time domain nuclear magnetic resonance (MQ TD-NMR) and by equilibrium swelling technique. The robustness and agreement of the two methods was demonstrated in measuring minute alterations of unfilled vulcanizates beyond the optimum cure time. Comparison with samples where polysulfidic bonds were selectively cleaved also demonstrates that the length of the sulfur chain constituting the cross-link does not significantly affect residual dipolar coupling. Kraus, Lorenz, and Parks correction for filler restriction on swelling is validated by MQ TD-NMR, which also allows extracting information on cross-link distribution not provided by swelling measurement. Cross-link distributions in the blends were demonstrated to be significantly different from the weighted average of the pure samples, while average proton–proton residual dipolar coupling values correspond. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42700.

In the search of new drug delivery carriers for the brain, self-assembled nanoparticles (NP) were prepared from poly(N,N-dimethylacrylamide)-block-polystyrene polymer. NP displayed biocompatibility on cultured endothelial cells, macrophages and differentiated SH-SY5Y neuronal-like cells. The surface-functionalization of NP with a modified fragment of human Apolipoprotein E (mApoE) enhanced the uptake of NP by cultured human brain capillary endothelial cells, as assessed by confocal microscopy, and their permeability through a Transwell Blood Brain Barrier model made with the same cells, as assessed by fluorescence. Finally, mApoE-NP embedding doxorubicin displayed an enhanced release of drug at low pH, suggesting the potential use of these NP for the treatment of brain tumors. In the search of novel drug carriers for brain drug delivery, poly(N,N-dimethylacrylamide)-b-polystyrene nanoparticles (NP) have been functionalized with a modified fragment of Apolipoprotein E (mApoE). These NP show to be uptaken and to overcome a Blood-Brain Barrier (BBB) in vitro cellular model. The cytotoxicity of NP is also investigated on different cell lines, showing high biocompatibility.

Controlled morphogenesis and shape replication are challenges for several rapidly developing fields of materials science. Indeed, although complex forms have been generated by the condensation of inorganic matter in organized media, the shaping of plastic matter on the micrometre scale is still limited to simple forms that are typically obtained as inverse replicas of channel-like cavities and colloidal crystals. Here we report the fabrication of individual plastic micro-objects that follow an elaborate design and are faithful copies of nanoporous inorganic morphotypes. The direct replica method produces an unprecedented library of curved geometrical solids made of plastics, such as cones, bicones, hollow cylinders, rings, test tubes, clubs and vases. The shape retention of the original structures on the microscale and the creation of a new nanostructure produced objects with homogeneous nanopores of 7 nm and cylindrical microcavities as large as 1 microm. This strategy of shape transcription from one material to another opens new perspectives in microfabrication, separation, anchorage and storage of chemical and biological species. Until now it has not been possible to realize such transformations.

Porous materials were prepd. using the novel polymorph of tris(o-phenylenedioxy)cyclophosphazene (TPP). The empty channellike structure was obtained from the hexagonal TPP/benzene inclusion compd. by mild evacuation of the volatile guest. Continuous flow laser-polarized 129Xe NMR spectroscopy is applied for the 1st time to study gas diffusion in the open-channel structure

The detailed analysis of the time resolved luminescence of a specifically designed fluorescent molecular rotor enables the direct monitoring of the self-assembly of a poly(N,N-dimethylacrylamide)-block-polystyrene (PDMA-b-PS) copolymer into core-corona nanoparticles. Comparison with bulk PS indicates hard confinement of the micelle core, due to the solvation of the hydrophilic PDMA corona.

PEGylation of metal oxide nanoparticles is the common approach to improve their biocompatibility and in vivo circulation time. In this work, we present a combined experimental and theoretical study to determine the operating condition that guarantee very high grafting densities, which are desirable in any biomedical application. Moreover, we present an insightful conformational analysis spanning different coverage regimes and increasing polymer chain lengths. Based on 13C NMR measurements and molecular dynamics simulations, we show that classical and popular models of polymer conformation on surfaces fail in determining the mushroom-to-brush transition point and prove that it actually takes place only at rather high grafting density values.