Polyolefin-based materials are increasingly being used in many industrial applications for packaging, automotive and construction materials. The recent developments of research have been aimed at making these materials, often complex, being mixtures, block copolymers, micro-and nanocomposites with inorganic and organic fillers, more efficient and environmentally friendly (through recycling processes, and the use of bio-polyolefins). In this context, functionalized polyolefins, on the one hand, play a fundamental role in improving the morphology and thus the thermal and mechanical properties of heterophase systems, and, on the other hand, provide new materials difficult to obtain by conventional synthesis in connection with the type of inserted functionality. Therefore it appears to be of interest to report and discuss here the recent results concerning the radical grafting in the melt of different functionalities onto polyolefins as well as the capability reached of modulating ad hoc the degree of grafting and the final structure/architecture of functionalized polyolefins.
Black
phosphorus (bP) has been recently investigated for next generation
nanoelectronic multifunctional devices. However, the intrinsic instability
of exfoliated bP (the bP nanoflakes) toward both moisture and air
has so far overshadowed its practical implementation. In order to
contribute to fill this gap, we report here the preparation of new
hybrid polymer-based materials where bP nanoflakes (bPn) exhibit a
significantly improved stability. The new materials have been prepared
by different synthetic paths including: (i) the mixing of conventionally
liquid-phase exfoliated bP (in dimethyl sulfoxide, DMSO) with poly(methyl
methacrylate) (PMMA) solution; (ii) the direct exfoliation of bP in
a polymeric solution; (iii) the in situ radical polymerization after
exfoliating bP in the liquid monomer (methyl methacrylate, MMA). This
last methodology concerns the preparation of stable suspensions of
bPn–MMA by sonication-assisted liquid-phase exfoliation (LPE)
of bP in the presence of MMA followed by radical polymerization. The
hybrids characteristics have been compared in order to evaluate the
bP dispersion and the effectiveness of the bPn interfacial interactions
with polymer chains aimed at their long-term environmental stabilization.
The passivation of the bPn is particularly effective when the hybrid
material is prepared by in situ polymerization. By using this synthetic
methodology, the nanoflakes, even if with a gradient of dispersion
(size of aggregates), preserve their chemical structure from oxidation
(as proved by both Raman and 31P-solid state NMR studies)
and are particularly stable to air and UV light exposure. The feasibility
of this approach, capable of efficiently exfoliating bP while protecting
the bPn, has been then verified by using different vinyl monomers
(styrene and N-vinylpyrrolidone), thus obtaining
hybrids where the nanoflakes are embedded in polymer matrices with
a variety of intriguing thermal, mechanical, and solubility characteristics.
Phosphorene, the 2D material derived from black phosphorus, has recently attracted a lot of interest for its properties, suitable for applications in materials science. The physical features and the prominent chemical reactivity on its surface render this nanolayered substrate particularly promising for electrical and optoelectronic applications. In addition, being a new potential ligand for metals, it opens the way for a new role of the inorganic chemistry in the 2D world, with special reference to the field of catalysis. The aim of this review is to summarize the state of the art in this subject and to present our most recent results in the preparation, functionalization, and use of phosphorene and its decorated derivatives. We discuss several key points, which are currently under investigation: the synthesis, the characterization by theoretical calculations, the high pressure behavior of black phosphorus, as well as its decoration with nanoparticles and encapsulation in polymers. Finally, device fabrication and electrical transport measurements are overviewed on the basis of recent literature and the new results collected in our laboratories.
Functionalized poly(butylene succinate) (PBS) samples were prepared by a post-polymerization method
based on the coupling reaction between TEMPO derivatives bearing different functionalities and
PBS macroradicals generated by H-abstraction using a peroxide. 4-Benzoyloxy-2,2,6,6-
tetramethylpiperidine-1-oxyl (BzO-TEMPO) and 4-(1-naphthoate)-2,2,6,6-tetramethylpiperidine-1-oxyl
(NfO-TEMPO), a pro-fluorescent nitroxide, were successfully grafted on PBS, as revealed by MALDI TOF
MS and UV-Vis spectroscopy. The functionalization degrees were accurately determined by UV-Vis
analysis and confirmed by 1H-NMR spectroscopy. The grafting site was identified by combining
theoretical calculations with experimental evidence. This evidence was collected by both EPR analysis of
a functionalized sample subjected to controlled heating in the EPR cavity, and by 1H-NMR spectroscopy.
Our functionalization method, which was also tested for poly(lactic acid) (PLA), preserves the original
polymer structure. This avoids the crosslinking-branching side reaction, which generally affects the free
radical treatment of biodegradable aliphatic polyesters. In addition, using a pro-fluorescent nitroxide to
form functionalized samples is a significant step towards unambiguously demonstrating the radical
grafting on these types of polymer. It also proves that well-defined fluorescently labeled biodegradable
polyesters can be tailored
A deepening insight the radical functionalization of poly(lactic acid) is here reported with new chemical approaches to control the grafting level and the ultimate structure by stabilizing the macroradical intermediates.
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