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Adding nanoparticles to a host polymer can lead to performance improvements that can be twice as beneficial to the environment: first, sustainable nanocomposites based on bioplastics or recycled plastics could replace ubiquitous petroleum-based polymers; second, substantial plastic saving could be achieved by profiting from the superior specific properties of the nanocomposites. Nevertheless, the inherent environmental burden of nanoparticles can compromise the expected benefits. Here we address the controversial issue of the environmental sustainability of “green” polymer nanocomposites based on bioplastics and recycled plastics. A critical review of life-cycle assessment studies regarding nanocomposites and their individual constituents is presented. Nanoparticles have a remarkable environmental impact despite their typically low content. Except for organo-clays and graphene, the production of common nanofillers (nanocellulose, titanium dioxide, silver and, above all, carbon nanotubes) emits relevant amounts of greenhouse gases and requires high energy, nullifying the advantages of using green polymer matrices. Reaching high performance becomes hence crucial to make polymer nanocomposites truly sustainable through material saving. For this purpose, increasing the content of nanoparticles or functionalizing them to enhance their dispersion in the host polymer can unexpectedly entail environmental benefits.

The photo-oxidative degradation processes of bio-based PA11 nanocomposites containing montmorillonite (MMT) and the organo-modified Cloisite&reg, 30B were investigated to discriminate the influence of organo-modified components on the polymer durability. Indeed, despite the extensive studies reported, there are still ambiguous points to be clarified from the chemical point of view. To this aim, UV-aged materials were analyzed by Size Exclusion Chromatography (SEC), Inductively Coupled Plasma&ndash, Mass Spectrometry (ICP-MS) and Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). This enabled determining changes in both chemical structure and Molar Masses (MMs) induced by light, heat and oxygen exposure. The addition of organo-modified nanoclays strongly affected the PA11 light durability, triggering the macromolecular chains scission due to the typical &alpha, H, Norrish I and II mechanisms. However, the main contribution in boosting the photo-oxidative degradation is induced by iron impurities contained into the clays. Conversely, thermo-oxidation process performed at 215 &deg, C was unambiguously affected by the presence of the organo-modifiers, whose presence determined an enhancement of crosslinking reactions.

The design of novel cryogels containing N‐methyl‐D‐glucamine (NMG) group was herein reported. The macroporous materials were prepared via sustainable and feasible cryopolymerization by using as co-monomers (4‐vinyl-benzyl)‐N‐methyl‐D‐glucamine (VbNMG) and 2-hydroxyethyl methacrylate (HEMA) at different percentages. Particularly, cryogel containing 100% of VbNMG (VbNMG-100) showed excellent ability in fast water uptake, removing arsenic (V) and chromium (VI) metal ions from it. Reusability up to six cycles was also demonstrated. The as-prepared materials were characterized by spectroscopic, thermal, and morphological analyses. The effect of initial oxyanions concentration, kinetic profiles, interfering anions (phosphate and sulphate) were investigated and adsorption/desorption studies were carried out. Equilibrium sorption results well fitted the Langmuir isotherm for both ions tested, showing a startling aptitude in arsenic (76.3 mg/g) as well as chromium (130.9 mg/g) sorption properties if compared with similar polymers as well as other materials. Exploiting its spongy nature, only 5 mins were needed to absorb contaminated medium releasing purified water by a simple squeezing. Most importantly, the sponge can be easily regenerated and reused again up to three times without the depletion of its efficiency.