Bio-Based Polyether from Limonene Oxide Catalytic ROP as Green Polymeric Plasticizer for PLA

In this work, the polymerization of Limonene Oxide (LO) has been achieved using an Earth abundant metal-based catalyst developed in our group, that is very active in ring opening polymerization (ROP) processes. The bio-based polylimonene ether (PLO) obtained had low molecular weight and good thermal properties, thus being a potential green polymeric additive for other bio-based polymers such as PLA. Hence, we have explored its ability to influence PLA properties. The addition of only 10 wt %, led to the modification and improvement of PLA properties in terms of flexibility, thermal stability, and hydrophobicity. The results obtained are promising and open up the potential industrial application of polylimonene oxide (PLO) for the melt-processing of blends based on PLA/PLO. These new materials are totally based on renewable sources and may be interesting for many applications where biodegradability and reduced water adsorption is required, such as food packaging or agricultural mulch films

Insight into the melt processed Polylimonene oxide/Polylactic acid blends

In this work, the polymerization of limonene oxide (LO) has been optimized at room temperature with two different aluminium-based catalysts [AlMeX{2,6-(CHPh$_2$)$_2$-4-tBu-C$_6$H$_2$O}] (X = Me (1), Cl (2)). A fully bio-based ether, polylimonene oxide (PLO), has been synthesized with low molecular weight and good thermal stability, being a potential sustainable polymeric additive for other bio-based and biodegradable polymers such as polylactic acid (PLA). Hence, we have explored its ability to influence the thermal, mechanical and morphological properties of PLA by preparing their blends by melt processing. The addition of a low amount of PLO led to a nearly 10 $^\circ$C decrease in the PLA glass transition temperature. Moreover, a decrease in the PLA melting temperature and the degree of crystallinity was observed. Interestingly, a remarkable increase in the flexibility of PLA-based films was noticed. All the results point to the existence of strong interactions between the components, suggesting their partial miscibility.Comment: Polymer Chemistry (2023

Observaciones del planetoide (51) Nemusa durante los años 1951-1954

Reaction of AlMe₃ with S­(SiMe₃)­(C₆H₃-2-CH₂NRR′-5-^<i>t</i>Bu) (RR′ = C₅H₁₀ (<b>1a</b>), C₄H₈ (<b>1b</b>), Me₂ (<b>1c</b>)), at ambient temperature, affords the amino adducts [AlMe₃{S­(SiMe₃)­(C₆H₃-2-CH₂NRR′-5-^<i>t</i>Bu)}-<i>κN</i>] (RR′ = C₅H₁₀ (<b>2a</b>), C₄H₈ (<b>2b</b>), Me₂ (<b>2c</b>)), which undergo TMS elimination upon heating to give the monomeric aminoarenethiolate aluminum complexes [AlMe₂{S­(C₆H₃-2-CH₂NRR′-5-^<i>t</i>Bu)-κ²<i>S,N</i>}] (RR′ = C₅H₁₀ (<b>3a</b>), C₄H₈ (<b>3b</b>), Me₂ (<b>3c</b>)). Following the same procedure, treatment of AlCl₂Me and AlCl₃ with <b>1</b> yields analogous aminoarenethiolate aluminum complexes with different degrees of methylation, the chloro methyl and dichloro complexes [AlClMe­{S­(C₆H₃-2-CH₂NRR′-5-^<i>t</i>Bu)-κ²<i>S,N</i>}] (RR′ = C₅H₁₀ (<b>4a</b>), C₄H₈ (<b>4b</b>), Me₂ (<b>4c</b>)) and [AlCl₂{S­(C₆H₃-2-CH₂NRR′-5-^<i>t</i>Bu)}-κ²<i>S,N</i>] (RR′ = C₅H₁₀ (<b>5a</b>), C₄H₈ (<b>5b</b>) Me₂ (<b>5c</b>)), respectively. These complexes have been characterized by multinuclear NMR spectroscopy and elemental analysis. Moreover, the molecular structures of <b>3a</b>,<b>b</b> have been determined by X-ray diffraction methods. Aluminum complexes <b>3</b> have been investigated for the ring-opening polymerization (ROP) of l-lactide, achieving high conversions in relatively short periods of time. The PLAs obtained feature an aminoarenethiolate end functionality, as inferred from MALDI-TOF mass analysis

Ring-Opening Polymerization of L-Lactide Catalyzed by Potassium-Based Complexes: Mechanistic Studies

Two non-toxic potassium compounds, 1 and 2, with a commercial oximate ligand have been prepared and fully spectroscopically characterized. Their activity as catalysts for the ring-opening polymerization (ROP) process of LLA has been studied, showing that they are extremely active and able to polymerize the monomer in a few minutes. For derivative 2, the presence of a crown ether in the potassium coordination sphere affects the nuclearity of the compound and consequently its solubility, with both aspects having an influence in the polymerization process. Detailed studies of the polymerization mechanism have been performed, and an unusual anionic mechanism was observed in absence of a co-initiator. Indeed, the monomer deprotonation generates a lactide enolate, which initiates the polymerization propagation. On the contrary, when a 1:1 ratio of cat:BnOH is used, a mixture of mechanisms is observed, the anionic mechanism and the activated monomer one, while from a cat:BnOH ratio of 1:2 and over, only the activated monomer mechanism is observed

Catalytic Formation of Cyclic Carbonates using Gallium Aminotrisphenolate Compounds and Comparison to their Aluminium Congeners: A Combined Experimental and Computational Study

Abstract: This work reports on the use of gallium aminotrisphenolate compounds as catalysts for the synthesis of cyclic carbonates from epoxides and CO2. The results show that they are highly active, and more so than the corresponding aluminium congeners. The catalyst system is applicable at low and elevated temperatures across a wide substrate scope including terminal, internal, multiple and fully deuterated epoxides. Applying low catalyst loadings has allowed for a TON of 344,000 to be obtained, highlighting their stability. A DFT investigation has confirmed that the gallium catalysts have lower energetic profiles compared to the aluminium congeners. Measurement of the Lewis acidity of both the gallium and aluminium aminotrisphenolate compounds using the Gutmann‐Beckett method provides the experimental proof that the gallium compounds are more Lewis acidic than their aluminium congeners. Finally, Ab‐Initio Molecular Dynamic (AIMD) simulations have investigated and quantified the dynamic behaviour of the catalytic systems, highlighting an important increase in fluxionality in some cases which helps to explain the increase in catalytic activity

The avoidance of G-CSF and the addition of prophylactic corticosteroids after autologous stem cell transplantation for multiple myeloma patients appeal for the at-home setting to reduce readmission for neutropenic fever

Background Autologous stem cell transplantation (ASCT) remains the standard of care for young multiple myeloma (MM) patients; indeed, at-home ASCT has been positioned as an appropriate therapeutic strategy. However, despite the use of prophylactic antibiotics, neutropenic fever (NF) and hospital readmissions continue to pose as the most important limitations in the outpatient setting. It is possible that the febrile episodes may have a non-infectious etiology, and engraftment syndrome could play a more significant role. The aim of this study was to analyze the impact of both G-CSF withdrawal and the addition of primary prophylaxis with corticosteroids after ASCT. Methods Between January 2002 and August 2018, 111 MM patients conditioned with melphalan were managed at-home beginning +1 day after ASCT. Three groups were established: Group A (n = 33) received standard G-CSF post-ASCT; group B (n = 32) avoided G-CSF post-ASCT; group C (n = 46) avoided G-CSF yet added corticosteroid prophylaxis post-ASCT. Results The incidence of NF among the groups was reduced (64%, 44%, and 24%; P2 (OR 6.1; P = 0.002) and G-CSF avoidance plus corticosteroids (OR 0.1; P60 years (OR 14.6; P = 0.04) and G-CSF avoidance plus corticosteroids (OR 0.07; P = 0.05). Conclusions G-CSF avoidance and corticosteroid prophylaxis post ASCT minimize the incidence of NF in MM patients undergoing at-home ASCT. This approach should be explored in a prospective randomized clinical trial

The first hominin of Europe

The earliest hominin occupation of Europe is one of the most debated topics in palaeoanthropology. However, the purportedly oldest of the Early Pleistocene sites in Eurasia lack precise age control and contain stone tools rather than human fossil remains(1-5). Here we report the discovery of a human mandible associated with an assemblage of Mode 1 lithic tools and faunal remains bearing traces of hominin processing, in stratigraphic level TE9 at the site of the Sima del Elefante, Atapuerca, Spain(6-8). Level TE9 has been dated to the Early Pleistocene ( approximately 1.2 - 1.1 Myr), based on a combination of palaeomagnetism, cosmogenic nuclides and biostratigraphy. The Sima del Elefante site thus emerges as the oldest, most accurately dated record of human occupation in Europe, to our knowledge. The study of the human mandible suggests that the first settlement of Western Europe could be related to an early demographic expansion out of Africa. The new evidence, with previous findings in other Atapuerca sites ( level TD6 from Gran Dolina(9-13)), also suggests that a speciation event occurred in this extreme area of the Eurasian continent during the Early Pleistocene, initiating the hominin lineage represented by the TE9 and TD6 hominins.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62855/1/nature06815.pd

Terpenes and Terpenoids: Building Blocks to Produce Biopolymers

Polymers are essential materials in our daily life. The synthesis of value-added polymers is mainly performed from fossil fuel-derived monomers. However, the adoption of the circular economy model based on the bioeconomy will reduce the dependence on fossil fuels. In this context, biorefineries have emerged to convert biomass into bioenergy and produce high value-added products, including molecules that can be further used as building blocks for the synthesis of biopolymers and bioplastics. The achievement of catalytic systems able to polymerize the natural monomer counterparts, such as terpenes or terpenoids, is still a challenge in the development of polymers with good mechanical, thermal, and chemical properties. This review describes the most common types of bioplastics and biopolymers and focuses specifically on the polymerization of terpenes and terpenoids, which represent a source of promising monomers to create bio-based polymers and copolymers

Conducting Polymer-Based Nanohybrids for Fuel Cell Application

Carbon materials such as carbon graphitic structures, carbon nanotubes, and graphene nanosheets are extensively used as supports for electrocatalysts in fuel cells. Alternatively, conducting polymers displayed ultrahigh electrical conductivity and high chemical stability havegenerated an intense research interest as catalysts support for polymer electrolyte membrane fuel cells (PEMFCs) as well as microbial fuel cells (MFCs). Moreover, metal or metal oxides catalysts can be immobilized on the pure polymer or the functionalized polymer surface to generate conducting polymer-based nanohybrids (CPNHs) with improved catalytic performance and stability. Metal oxides generally have large surface area and/or porous structures and showed unique synergistic effects with CPs. Therefore, a stable, environmentally friendly bio/electro-catalyst can be obtained with CPNHs along with better catalytic activity and enhanced electron-transfer rate. The mass activity of Pd/polypyrrole (PPy) CPNHs as an anode material for ethanol oxidation is 7.5 and 78 times higher than that of commercial Pd/C and bulk Pd/PPy. The Pd rich multimetallic alloys incorporated on PPy nanofibers exhibited an excellent electrocatalytic activity which is approximately 5.5 times higher than monometallic counter parts. Similarly, binary and ternary Pt-rich electrocatalysts demonstrated superior catalytic activity for the methanol oxidation, and the catalytic activity of Pt24Pd26Au50/PPy significantly improved up to 12.5 A per mg Pt, which is approximately15 times higher than commercial Pt/C (0.85 A per mg Pt). The recent progress on CPNH materials as anode/cathode and membranes for fuel cell has been systematically reviewed, with detailed understandings into the characteristics, modifications, and performances of the electrode materials

Conjugated polymer nanostructures displaying highly photoactivated antimicrobial and antibiofilm functionalities

This work reports the use of conjugated polymer nanostructures (CPNs) as photoactivated antimicrobial compounds against Gram-positive and Gram-negative microorganisms. Two representative CPNs of polythiophene (PEDOT) and polyaniline (PANI) were prepared as nanofibres with an average diameter of 40 nm and length in the micrometer range. Both CPNs exhibited strong antimicrobial activity under UVA irradiation with the same fluence rate as the UVA component of the solar spectrum. The effect was tested using the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Escherichia coli. The reduction of colony forming units (CFUs) reached >6 log for PEDOT concentrations as low as 33 ng mL(-1). For PEDOT nanofibers, a complete inhibition of S. aureus and E. coli growth was reached at 883 ng mL(-1) and 333 ng mL(-1) respectively. The photoactivation effect of PANI nanofibres on S. aureus and E. coli was also high, with a CFU reduction of about 7 log and 4 log respectively for an exposure concentration of 33 ng mL(-1). The antimicrobial activity was only high under light irradiation and was almost negligible for bulk PEDOT and PANI. The effect of polymeric nanofibers could be attributed to the photoinduced generation of reactive oxygen species, which may induce cell membrane damage, eventually leading to bacterial impairment and inhibition of their biofilm forming capacity. CPN PEDOT and PANI coatings were able to keep surfaces free of bacterial attachment and growth even after 20 h of previous contact with exponentially growing cultures in the dark. PEDOT and PANI CPNs demonstrated good cytocompatibility with human fibroblasts and the absence of hemolytic activity. The materials demonstrated advantages in terms of broad antibacterial spectrum, biofilm inhibition, and the absence of acute toxicity for biomedical applications