Explore the vast range of titles available.

Problems related to non-biodegradable waste coming from vulcanized rubber represent one of the pre-eminent challenges for modern society. End-of-life tyres are an important source of this typology of waste and the increasingly high accumulation in the environment has contributed over the years to enhance land and water pollution. Moreover, the release into the environment of non-degradable micro-plastics and other chemicals as an effect of tyre abrasion is not negligible. Many solutions are currently applied to reuse end-of-life tyres as a raw material resource, such as pyrolysis, thermo-mechanical or chemical de-vulcanisation, and finally crumbing trough different technologies. An interesting approach to reduce the environmental impact of vulcanised rubber wastes is represented by the use of degradable thermoplastic elastomers (TPEs) in tyre compounds. In this thematic review, after a reviewing fossil fuel-based TPEs, an overview of the promising use of degradable TPEs in compound formulation for the tyre industry is presented. Specifically, after describing the properties of degradable elastomers that are favourable for tyres application in comparison to used ones, the real scenario and future perspectives related to the use of degradable polymers for new tyre compounds will be realized.

Linear aliphatic polyesters are degradable thermoplastic polymers, which can be obtained by ring-opening polymerization (ROP) of cyclic esters through a coordination-insertion mechanism. Aluminum based organometallic complexes have a leading position as efficient catalysts for this polymerization process. Aluminumalkyl complexes bearing salicylaldiminato ligands, although less explored, have been shown to be efficient and versatile catalysts for the ROP of various cyclic esters. These species have the potential to function as active catalysts in the ROP because of their less coordinatively saturated nature with respect to analogous SALEN-type complexes. They have been used as efficient catalysts in the ROP of commercially available cyclic esters, such as ε-caprolactone, l-lactide, rac-lactide, and glycolide. Moreover, they resulted in efficient catalysts for the ROP of cyclic esters with large ring-size and for the ROP of functionalized lactide. Furthermore, they have been used in the co- and ter-polymerization of various cyclic esters affording well controlled polymerization and a plethora of microstructural architectures, ranging from random to block to multiblock.

Biodegradable block and random copolymers have attracted numerous research interests in different areas, due to their capability to provide a broad range of properties. In this paper, an efficient strategy has been reported for preparing biodegradable PCL-PLA copolymers with improved thermal, mechanical and rheological properties. Two block-copolymers are synthesized by sequential addition of the cyclic esters lactide (L-LA or D,L-LA) and ε-caprolactone (CL) in presence of a dimethyl(salicylaldiminato)aluminium compound. The random copolymer of L-LA and CL was synthetized by using the same catalyst. Chain structure, molar mass, thermal, rheological and mechanical properties are characterized by NMR, SEC, TGA, DSC, Rheometry and DMTA. Experimental results show that by changing the stereochemistry and monomer distribution of the copolymers it is possible to obtain a variety of properties. Promising shape-memory properties are also observed in the di-block copolymers characterized by the co-crystallization of CL and L-LA segments. These materials show great potential to substitute oil-based polymers for packaging, electronics, and medicine applications.

Chromium and aluminum complexes bearing salalen ligands were explored as catalysts for the ring-opening copolymerization (ROCOP) of succinic (SA), maleic (MA), and phthalic (PA) anhydrides with several epoxides: cyclohexene oxide (CHO), propylene oxide (PO), and limonene oxide (LO). Their behavior was compared with that of traditional salen chromium complexes. A completely alternating enchainment of monomers to provide pure polyesters was achieved with all the catalysts when used in combination with 4-(dimethylamino)pyridine (DMAP) as the cocatalyst. Poly(propylene maleate-block-polyglycolide), a diblock polyester with a precise composition, was obtained by switch catalysis, in which the same catalyst was able to combine the ROCOP of propylene oxide and maleic anhydride with the ring-opening polymerization (ROP) of glycolide (GA) through a one-pot procedure, starting from an initial mixture of the three different monomers.

Quercetin is a hydrophobic molecule with short blood circulation times and instability. The development of a nano-delivery system formulation of quercetin may increase its bioavailability, resulting in greater tumor suppressing effects. Triblock ABA type polycaprolactone-polyethylenglycol- polycaprolactone (PCL-PEG-PCL) copolymers have been synthetized using ring-opening polymerization of caprolactone from PEG diol. The copolymers were characterized by nuclear magnetic resonance (NMR), diffusion-ordered NMR spectroscopy (DOSY), and gel permeation chromatography (GPC). The triblock copolymers self-assembled in water forming micelles consisting of a core of biodegradable polycaprolactone (PCL) and a corona of polyethylenglycol (PEG). The core-shell PCL-PEG-PCL nanoparticles were able to incorporate quercetin into the core. They were characterized by dynamic light scattering (DLS) and NMR. The cellular uptake efficiency of human colorectal carcinoma cells was quantitatively determined by flow cytometry using nanoparticles loaded with Nile Red as hydrophobic model drug. The cytotoxic effect of quercetin-loaded nanoparticles was evaluated on HCT 116 cells, showing promising results.

The synthesis of novel block copolymers, namely poly(limonene-phthalate)-block-poly(pentadecalactone) and poly(limonene-phthalate)-block-poly(pentadecalactone) is here described. To achieve this synthesis, a bimetallic aluminum based complex (1) was used as catalyst in the combination of two distinct processes: the ring-opening polymerization (ROP) of macrolactones such as ω-pentadecalactone (PDL) and ω-6-hexadecenlactone (HDL) and the ring-opening copolymerization (ROCOP) of limonene oxide (LO) and phthalic anhydride (PA). The synthesis of di-block polyesters was performed in a one-pot procedure, where the semi-aromatic polyester block was firstly formed by ROCOP of LO and PA, followed by the polyethylene like portion produced by ROP of macrolactones (PDL or HDL). The obtained di-block semiaromatic polyesters were characterized by NMR and GPC. The structural organization was analyzed through XRD. Thermal properties were evaluated using differential thermal analysis (DSC) and thermogravimetric measurements (TGA) either in air or in nitrogen atmosphere.

Quercetin is a hydrophobic molecule with short blood circulation times and instability. The development of a nano-delivery system formulation of quercetin may increase its bioavailability, resulting in greater tumor suppressing effects. Triblock ABA type polycaprolactone-polyethylenglycol- polycaprolactone (PCL-PEG-PCL) copolymers have been synthetized using ring-opening polymerization of caprolactone from PEG diol. The copolymers were characterized by nuclear magnetic resonance (NMR), diffusion-ordered NMR spectroscopy (DOSY), and gel permeation chromatography (GPC). The triblock copolymers self-assembled in water forming micelles consisting of a core of biodegradable polycaprolactone (PCL) and a corona of polyethylenglycol (PEG). The core-shell PCL-PEG-PCL nanoparticles were able to incorporate quercetin into the core. They were characterized by dynamic light scattering (DLS) and NMR. The cellular uptake efficiency of human colorectal carcinoma cells was quantitatively determined by flow cytometry using nanoparticles loaded with Nile Red as hydrophobic model drug. The cytotoxic effect of quercetin-loaded nanoparticles was evaluated on HCT 116 cells, showing promising results.

Decontaminating coating systems (DCSs) represent a challenge against pathogenic bacteria that may colonize hospital surfaces, causing several important infections. In this respect, surface coatings comprising photosensitizers (PSs) are promising but still controversial for several limitations. PSs act through a mechanism of antimicrobial photodynamic inactivation (aPDI) due to formation of reactive oxygen species (ROS) after light irradiation. However, ROS are partially deactivated during their diffusion through a coating matrix; moreover, coatings should allow oxygen penetration that in contact with the activated PS would generate 1O2, an active specie against bacteria. In the attempt to circumvent such constraints, we report a spray DCS made of micelles loaded with a PS belonging to the BODIPY family (2,6-diiodo-1,3,5,7-tetramethyl-8-(2,6-dichlorophenyl)-4,4′-difluoroboradiazaindacene) that is released in a controlled manner and then activated outside the coating. For this aim, we synthesized several amphiphilic copolymers (mPEG–(PLA)n), which form micelles, and established the most stable supramolecular system in terms of critical micelle concentration (CMC) and ∆Gf values. We found that micelles obtained from mPEG–(PLLA)2 were the most thermodynamically stable and able to release BODIPY in a relatively short period of time (about 80% in 6 h). Interestingly, the BODIPY released showed excellent activity against Staphylococcus aureus even at micromolar concentrations.