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Isotactic polypropylene (iPP) gives very extensive degradation when treated with peroxides above its melting temperature in mechanical mixers or extruders. This undesired reaction is very modestly affected by maleate molecules which on the contrary actively compete with side reactions of macroradicals in the case of ethylene polymers. In this work iPP was treated in a Brabender mixer at 180 °C with peroxide and different selected molecules capable of promptly reacting with the macroradical formed on iPP chain and converting it into a more stable free radical. Furan derivatives, successfully used for iPP cross-linking without any remarkable increase of MFR, were used as free radical removers and maleic anhydride as functionalizing monomer. The results indicate a detectable improvement with respect to the use of maleic monomers and peroxide only, allowing to us get a significant grafting of functional groups and only partial degradation. Moreover, furan derivatives bearing various reactive substituents were used as functionalizing molecules. The results are discussed in the frame of the general mechanism proposed for the free radical functionalization of polyolefin in the melt.

Polyolefins are today the most used thermoplastic materials thanks to the high technology and sustainability of the polymerization process, their excellent thermomechanical properties and their good environmental compatibility, including easy recycling. In the last few decades much effort has been devoted worldwide to extend the applications of polyolefins by conferring on them new properties through mixing and blending with different materials. In this latter context, nanocomposites have recently offered new exciting possibilities. This has been made possible on the basis of the improvement of polyolefin functionalization processes with the availability of several olefin homo- and copolymers bearing a small (generally less than 1 mol%) amount of backbone grafted polar groups. These are indeed adequate to endow favourable interface interactions with polar macromolecules and inorganic compounds, leading first to compatible blends and then to microcomposites. The successful use of nanostructured dispersed materials has opened, on a similar basis, the way to nanocomposites as described in this review. This review provides a broad and updated description of the synthetic routes to nanostructured biphase materials having the typical structural properties of polyolefins (continuous matrix) but showing enhanced thermomechanical properties, thermostability, lower flammability, lower gas permeability and electrical and optical properties, thanks to the presence of an extended interphase interaction with very different nanodispersed species.\ud \ud  2008 Society of Chemical Industr

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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.

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