Low Molecular Weight Oligomers Research Articles

Template Assisted Synthesis of Linear [5]Catenane by Post-Functionalization of Templated [2]Catenane and Using Click Reaction.

Polymers with all mechanically interlocked rings, such as linear [n]catenanes, have great potential as functional materials due to possible higher degrees of freedom that may contribute to their flexibility but remain elusive. All the synthetic methods used to prepare such a polymer yield mixtures of products.In the absence of higher molecular weight linear [n]catenanes, emphasis on synthesizing low molecular weight oligomers is being pursued. Here, we have described the synthesis of a linear [5]catenane by post-functionalizing a Co(III) templated [2]catenane having a pyridine-diamide unit free for further metal ion coordination. Two molecules were synthesized with suitable threading groups: one, two terminal azide groups, and two, with two terminal alkyne groups to form two [3]pseudorotaxane utilizing Co(III) coordination. These units were then joined, forming a macrocycle, using click reaction, giving the desired metallated linear [5]catenane in 40% yield. Removal of metal ions leads to linear [5]catenane. In addition, the formation of linear [3] and [2]catenane are also observed. All synthesized structures have been isolated by column chromatographic technique and characterized by1H-NMR,13C-NMR, and mass spectroscopy.

Stereoselective Ring Expansion Metathesis Polymerization with Cationic Molybdenum Alkylidyne N-Heterocyclic Carbene Complexes.

Molybdenum alkylidyne N-heterocyclic carbene (NHC) complexes of the type [Mo(C-p-C6H4Y)(OC(R)(CF3)2)2 (L)(NHC)][B(ArF)4] (Y = OMe, NO2; R = CH3, CF3; L = none, pivalonitrile, tetrahydrofuran; NHC = 1,3-dimesitylimidazol-2-ylidene (IMes), 1,3-dimesityl-3,4-dihydroimidazol-2-ylidene (IMesH2), 1,3-dimesityl-3,4-dichloroimidazol-2-ylidene (IMesCl2), 1,3-diisopropylimidazol-2-ylidene (IiPr); B(ArF)4- = tetrakis(3,5-bis(trifluoromethyl)phen-1-yl)borate) were used in the ring expansion metathesis polymerization (REMP) of cyclic olefins. With cis-cyclooctene (cCOE) cyclic, low molecular weight oligomers were obtained at low monomer concentrations and the cyclic nature of the polymer was confirmed by MALDI-TOF measurements. High-molecular weight cyclic poly(cCOE) became available at high monomer concentrations. Also, post-REMP allowed for converting low-molecular-weight cyclic poly(cCOE) into high-molecular-weight cyclic poly(cCOE). Tailored catalysts together with suitable additives offered access to the stereoselective REMP of functional norbornenes providing functional cis-isotactic (cis-it), cis-syndiotactic (cis-st) and trans-it poly(norbornene)s with up to 99% stereoselectivity. Mechanistic details supported by density functional theory (DFT) calculations are outlined.

Fire retardants giving special properties to fibers and textile materials based on them

The fire-retardant properties of modified polyacrylonitrile fibers with phosphorus-containing polymers, as well as nitrogen and brominecontaining flame retardants, have been studied. It has been shown that, in contrast to low molecular weight fire retardants, polymer and oligomer fire retardants give fibers higher fire-retardant properties. The results of determining the flammability of samples showed that the treatment of polyacrylonitrile fibers with oligomeric flame retardants based on the developed flame retardants improves the fire-retardant properties of fibers and materials based on them. As a result of comprehensive research, it was established that for the manufacture of fire-resistant material it is advisable to use the optimal ratio of “polyacrylonitrile fiber - fire retardant”. Carrying out fire-retardant treatment of polyacrylonitrile material with compositions of 3-chloro-1,2-hydroxypropane with 2,4,6-triamino-1,3,5-triazine makes it possible to obtain fabrics with a reduced fire hazard and with the required strength parameters. Also, in the work, based on kinetic and spectroscopic studies and taking into account literature data, a mechanism of oligomeric fire retardant is proposed, which gives fibers and textile materials special fire resistance properties.

Size effects in 3D‐printed polymer‐derived, zirconium diboride‐reinforced ceramic composites

AbstractPreceramic polymers are of interest for use in many manufacturing techniques such as injection molding, ceramic fiber infiltration, and additive manufacturing. However, off‐gassing of low molecular weight oligomers occurs when these polymers cure, potentially leading to porosity in the cured part. To study how porosity and strength are affected by the size of the printed part, and the presence of a high surface area nano‐scale filler, polycarbosilane (PCS) microrods of varying diameter were fabricated via direct ink writing (DIW), an additive manufacturing technique, with two ink formulations containing either zirconium diboride (ZrB2) alone, or ZrB2 and fumed alumina (FA). Sets of microrods were printed in a range of sizes by using print nozzles of 450, 634, 979, 1 346, or 1 702 μm in diameter, which were thermally cured, pyrolyzed to form ceramic composite microrods, and tested in 3‐pt flexure. Porosity increased with increasing diameter, while failure strength decreased. For a given nozzle size, the microrods containing FA displayed lower porosity and higher strength (up to ∼500 MPa) compared to the microrods containing only ZrB2. Weibull strength analysis was performed on each group of microrods and shows that the addition of FA increased Weibull modulus from 4.63 ± 1.56 to 9.35 ± 0.601. In conjunction with optical microscopy, this analysis indicates two distinct flaw populations in the printed materials, porosity which arises during the curing step and cracking which arises during pyrolysis of the larger specimens.

Potential of Lauryl Gallate as Stability and Recyclability Improver of Poly (Butylene succinate-co-adipate)

In the present study, Lauryl Gallate (LG), a natural antioxidant, was used to improve polymer thermal stability and recyclability of a biodegradable polyester as poly(butylene succinate-co-adipate) (PBSA). Neat PBSA and PBSA/LG (0.5 wt% LG) blends were processed by melt extrusion and subjected to multiple consecutive extrusion cycles at 170 °C to prevent the occurrence of thermo-oxidative radical degradation processes of the polymer. Thermal, rheological, morphological, FTIR, and GPC analyses showed the beneficial effect of LG in delaying PBSA thermo-oxidative degradation, reducing polymer fragmentation at low-mid molecular weights compared to the reprocessed virgin PBSA. The use of LG limits the drop of both complex viscosity η* and zero-shear stress viscosity η0 as well as the reduction of crystallinity degree and the enhancement of melt flow rate (MFR). This molecular degradation produces low molecular weight polymer fractions and oligomers that solely affect molten PBSA fluidity. In the presence of 0.5 wt% of LG, the processability of PBSA doubles from six (neat PBSA) up to twelve extrusions until presenting the first signs of degradation of the molten polymer while preserving the mechanical characteristics at the solid state. These mechanical properties remain equivalent to the neat PBSA (Young’s modulus 0.33 GPa, yield strength 19.2 MPa, stress at break 24.4 MPa, and elongation at break 350%). Consequently, LG can be successfully employed as a natural PBSA stabilizer to extend the polymer lifecycle and contribute to the circular economy practice within the processing and manufacturing industry, particularly in the field of PBSA agricultural applications and injection moulded disposable products.

Steric and electronic effects in cationic pyridine carboxamidate nickel mediated ethylene polymerization and copolymerization with methyl 10-undecenoate

Improvement of catalysts performance by structural modification is a well recognised and more reliable way in catalysis. Amide derived catalysts were already used in olefin polymerization but possessed many limitation regarding to their poor thermal stability and mostly generating low molecular weight oligomers. Steric and electronic factors have played a characteristic role to control the catalyst stability, activity, molecular weight and branch densities of the polymers. So in continuity of our interest to improve the performance of olefin polymerization catalysts, we contributed here by synthesized cationic nickel catalysts (Ni1–Ni3) by simple amidation of picolinoyl chloride with sterically bulky and electronically varied anilines. Effect of steric and electronic factors also has been explored. Compared with previously reported sterically open pyridine carboxamidate nickel catalysts, these bulky nickel catalysts have two orders of magnitude higher activity of up to 3.73× 106 g (mol Ni)−1 h−1 towards ethylene polymerization and thermal stability up to 80 °C, producing higher molecular weight semi-crystalline polyethylene with tunable branching densities (17–67 branches/1000C) and melting points (65–121 °C). Moreover, these cationic nickel catalysts also promote the copolymerization of ethylene and methyl 10-undecenoate (MU) to afford polar functionalized polyethylenes with maximum incorporation of MU up to 1.53 mol%.

Visible Light Induced Degradation of Poly(methyl methacrylate-co-methyl α-chloro acrylate) Copolymer at Ambient Temperature.

Poly(methyl methacrylate) (PMMA) is a well-known and widely used commodity plastic. High production amount of PMMA causes excessive waste creation that highlights the necessity of recycling. Conventional recycling methods require elevated temperatures to induce degradation or depolymerization. In this work, visible light induced photodegradation system by using dimanganese decacarbonyl (Mn2 (CO)10 ) with high halogen affinity is reported. Halide functional photodegradable polymers are prepared by copolymerization of methyl methacrylate and methyl α-chloroacrylate by conventional reversible addition-fragmentation chain-transfer polymerization. Synthesized copolymers are efficiently degraded to low molecular weight oligomers under visible light irradiation in the presence of Mn2 (CO)10 . Characteristics of precursors, degraded polymers, and kinetics of depolymerization are investigated by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourrier transform infrared (FTIR), and proton nuclear magnetic resonance (1 H-NMR) spectroscopies. The reported approach is expected to trigger further development of more environmentally friendly recycling techniques in the near future as we are moving toward a greener and more sustainable world.

Peptide Models of the Cytoplasmic Tail of Influenza A/H1N1 Virus Hemagglutinin Expand Understanding its pH-Dependent Modes of Interaction with Matrix Protein M1.

Influenza A virus hemagglutinin (HA) is a major virus antigen. No cryo-electron microscopy or X-ray data can be obtained for the HA intraviral (cytoplasmic) domain (CT) post-translationally modified with long fatty acid residues bound to three highly conserved cysteines. We recently proposed a model of HA CT of Influenza A/H1N1 virus possessing an antiparallel beta structure based on the experimental secondary structure analysis of four 14-15 amino acid long synthetic peptides, corresponding to the HA CT sequence, with free or acetaminomethylated cysteines. To dispel doubts about possible non-specific "amyloid-like" aggregation of those synthetic peptides in phosphate buffer solution, we have determined the order of oligomers based on blue native gel electrophoresis, membrane filtration, fluorescence spectroscopy and molecular modeling approaches. We have found that unmodified peptides form only low molecular weight oligomers, while modified peptides form both oligomers of low order similar to those found for unmodified peptides and high order conglomerates, which however are not of beta-amyloid-like fold. This study confirms that the beta structure previously detected by circular dichroism spectroscopy analysis is more likely the result of intrinsic propensity of the HA CT amino acid sequence than the consequence of aggregation. The structures of low order oligomers of the synthetic peptides were used for in silico experiments on modeling of HA CT interactions with matrix protein M1 at physiological and acidic pH levels and revealed two different areas of binding. Finally, tripeptides capable of blocking interactions between HA CT and M1 were proposed.

Epsilon-Caprolactam- and Nylon Oligomer-Degrading Bacterium Brevibacterium epidermidis BS3: Characterization and Potential Use in Bioremediation.

epsilon-Caprolactam (Caprolactam, CAP), a monomer of the synthetic non-degradable polymer nylon-6, is the major wastewater component in the production of caprolactam and nylon-6. Biological treatment of CAP, using microbes could be a potent alternative to the current waste utilization techniques. This work focuses on the characterization and potential use of caprolactam-degrading bacterial strain BS3 isolated from soils polluted by CAP production wastes. The strain was identified as Brevibacterium epidermidis based on the studies of its morphological, physiological, and biochemical properties and 16S rRNA gene sequence analysis. This study is the first to report the ability of Brevibacterium to utilize CAP. Strain BS3 is an alcalo- and halotolerant organism, that grows within a broad range of CAP concentrations, from 0.5 up to 22.0 g/L, optimally at 1.0-2.0 g/L. A caprolactam biodegradation experiment using gas chromatography showed BS3 to degrade 1.0 g/L CAP over 160 h. In contrast to earlier characterized narrow-specific CAP-degrading bacteria, strain BS3 is also capable of utilizing linear nylon oligomers (oligomers of 6-aminohexanoic acid), CAP polymerization by-products, as sole sources of carbon and energy. The broad range of utilized toxic pollutants, the tolerance for high CAP concentrations, as well as the physiological properties of B. epidermidis BS3, determine the prospects of its use for the biological cleanup of CAP and nylon-6 production wastes that contain CAP, 6-aminohexanoic acid, and low molecular weight oligomer fractions.

Multistep sequence-controlled supramolecular polymerization by the combination of multiple self-assembly motifs

The precise sequence control of polymer chain is an important research topic of polymer chemistry. Although some methods such as iterative synthesis and supramolecular polymerization have been developed to fabricate sequence-controllable polymer, it is still a great challenge to consecutively prepare multiple supramolecular polymers with different sequence structures. In this work, through the reasonable utilization of assembly motifs, we integrated multiple host-guest recognitions and metal coordination interactions to prepare different sequence-controlled supramolecular polymers by a multistep assembly strategy. This research provides inspiration for the design and preparation of supramolecular polymers with different sequence structures.

Differentiation of subnucleus-sized oligomers and nucleation-competent assemblies of the A[formula omitted] peptide

A significant feature of Alzheimer’s disease is the formation of amyloid deposits in the brain consisting mainly of misfolded derivatives of proteolytic cleavage products of the amyloid precursor protein amyloid-β (Aβ) peptide. While high-resolution structures already exist for both the monomer and the amyloid fibril of the Aβ peptide, the mechanism of amyloid formation itself still defies precise characterization. In this study, low and high molecular weight oligomers (LMWOs and HMWOs) were identified by sedimentation velocity analysis, and for the first time, the temporal evolution of oligomer size distributions was correlated with the kinetics of amyloid formation as determined by thioflavin T-binding studies. LMWOs of subnucleus size contain fewer than seven monomer units and exist alongside a heterogeneous group of HMWOs with 20–160 monomer units that represent potential centers of nucleus formation due to high local monomer concentrations. These HMWOs already have slightly increased β-strand content and appear structurally similar regardless of size, as shown by examination with a range of fluorescent dyes. Once fibril nuclei are formed, the monomer concentration begins to decrease, followed by a decrease in oligomer concentration, starting with LMWOs, which are the least stable species. The observed behavior classifies the two LMWOs as off pathway. In contrast, we consider HMWOs to be on-pathway, prefibrillar intermediates, representing structures in which nucleated conformational conversion is facilitated by high local concentrations. Aβ40 and Aβ42 M35ox take much longer to form nuclei and enter the growth phase than Aβ42 under identical reaction conditions, presumably because both the size and the concentration of HMWOs formed are much smaller.

Concentration Effect, Structural Properties, and Driving Force on Aβ28 Dimerization with and without Zn2+ Cooperation: Learning from Replica Exchange Sampling.

Zn2+ is a very important factor in promoting the formation of amyloid beta (Aβ) aggregates and amyloid plaques. The Zn2+ -bound Aβ species generate amorphous or low molecular-weight oligomers. However, it is a lack of studies to approach the starting structural features (dimerization) in Aβ nucleation processes with and without Zn2+ , which is the key point in understanding Zn2+ -induced nucleation mechanisms. To better understand the effect of concentration, structural properties, and the driving force, 14 independent replica exchange molecular dynamics simulations were performed in Aβ28 dimerization with and without Zn2+ (zAβ28 ) cooperation. Our scanning results show that the aggregation propensity is easier in Aβ28 -Aβ28 and Aβ28 -zAβ28 systems than zAβ28 -zAβ28 system. In binding property, the Aβ28 -Aβ28 model (-61.5 kcal mol-1 ) is stronger than zAβ28 -zAβ28 (-26.6 kcal mol-1 ) and Aβ28 -zAβ28 (-7.24 kcal mol-1 ) models. Further analysis confirmed that H13 and H14 residues play specific roles in the three systems. The key point is the orientation of N atom of the imidazole ring in histidine residues. Furthermore, we discovered different driving forces for each system. Our current study contributes to the understanding of how the Aβ28 dimer interacts with Zn2+ , which could lead to new insights into Zn2+ -induced nucleation mechanisms.

The co-effect of copper and lipid vesicles on Aβ aggregation

Both metal ions and lipid membranes have a wide distribution in amyloid plaques and play significant roles in AD pathogenesis. Although influences of different metal ions or lipid vesicles on the aggregation of Aβ peptides have been extensively studied, their combined effects are less understood. In this study, we reported a unique effect of copper ion on Aβ aggregation in the presence of lipid vesicles, different from other divalent metal ions. Cu2+ in a super stoichiometric amount leads to the rapid formation of β-sheet rich structure, containing abundant low molecular weight (LMW) oligomers. We demonstrated that oligomerization of Aβ40 induced by Cu2+ binding was an essential prerequisite for the rapid conformation transition. Overall, the finding provided a new view on the complex triple system of Aβ, copper ion and lipid vesicles, which might help understanding of Aβ pathologies.

Development of β-sheet structure in Aβ aggregation intermediates diminishes exposed hydrophobic surface area and enhances proinflammatory activity

Three decades of research, both in vitro and in vivo, have demonstrated the conformational heterogeneity that is displayed by the amyloid β peptide (Aβ) in Alzheimer's disease (AD). Understanding the distinct properties between Aβ conformations and how conformation may impact cellular activity remain open questions, yet still continue to provide new insights into protein misfolding and aggregation. In particular, there is interest in the group of soluble oligomeric prefibrillar Aβ species comprising lower molecular weight oligomers up to larger protofibrils. In the current study, a number of strategies were utilized to separate Aβ protofibrils and oligomers and show that the smaller Aβ oligomers have a much different conformation than Aβ protofibrils. The differences were consistent for both Aβ40 and Aβ42. Protofibrils bound thioflavin T to a greater extent than oligomers, and were highly enriched in β-sheet secondary structure. Aβ oligomers possessed a more open structure with significant solvent exposure of hydrophobic domains as determined by tryptophan fluorescence and bis-ANS binding, respectively. The protofibril-selective antibody AbSL readily discerned conformational differences between protofibrils and oligomers. The more developed structure for Aβ protofibrils ultimately proved critical for provoking the release of tumor necrosis factor α from microglial cells. The findings demonstrated a dependency on β-sheet structure for soluble Aβ aggregates to cause a microglial inflammatory response. The Aβ aggregation process yields many conformationally-varied species with different levels of β-structure and exposed hydrophobicity. The conformation elements likely determine biological activity and pathogenicity.

Beyond PEO: New Safe Solid Polymer Electrolytes for Decreasing the Operational Temperature of All Solid-State Lithium Ion Batteries

In a world with a growing demand in energy and a great dependence on limited fossil fuels, electrochemical energy storage arises as the key alternative to meet the needs of current society. In particular, lithium batteries stand out among all the available energy-storage technologies. For the last two decades, lithium-ion batteries (LIBs) have become the dominative components in portable electronic devices.As one of the most critical components, the choice of the electrolyte plays a pivotal role for preparing safe and high performance LIBs. Most of the commercial lithium batteries are built up with liquid electrolytes, which entails potential security risks such as volatilization, flammability and explosion. For this reason, numerous research efforts are focused on the obtaining of solvent-free solid electrolytes. Solid polymer electrolytes (SPEs) are considered as one of the most viable solutions to replace their liquid counterparts. SPEs have many advantages over conventional liquid electrolytes such as high energy density, low reactivity with the electrodes, and the mitigation of the Li dendrite growth. Additionally, in contrast to inorganic solid electrolytes, SPEs can attenuate the interfacial resistance and improve the electrode-electrolyte compatibility compared to ceramic electrolytes.Among all the existing polymer hosts for SPEs, poly(ethylene oxide) (PEO) is the most commonly used one due to its strong solvation ability that facilitates the dissociation of various lithium salts. However, PEO lacks some essential requirements when considering it as an ideal host material for SPE; namely the low Li-ion conductivity at ambient temperature due to its crystalline nature. Thus, the low Li-ion conductivity of SPEs at ambient temperature remains as the major hindrance towards the practical deployment of lithium polymer batteries.1, 2 In addition, the anion concentration gradient that takes place in conventional dual-ion conductors is one of the factors responsible for low Li-ion transference number (T Li + < 0.5) and consequently are more susceptible to polarization phenomena that eventually limit the power density and cycle life of lithium batteries. The main strategy to go through this polarization problem is the development of single lithium-ion conducting solid polymer electrolytes (SLIC-SPEs), where the anion is immobilized by different means.3 In order to overcome this drawback, tremendous efforts have been dedicated to the design and synthesis of new polymeric matrices that allow obtaining SPEs with improved ionic conductivity at room temperature, where modification such as cross-linking or copolymerization, or the use of low molecular weight oligomers are the main used strategies. Inspired by previously stated challenges, in the present work we will present the performance of novel flexible and highly conductive SPEs with the purpose of decreasing the working temperature. Moreover, taking advantage of the good conductivity of the synthesized polymer host, the role of different additives on the performance of newly synthesized SLIC-SPEs is provided.

Effective viscosification of supercritical carbon dioxide by oligomers of 1-decene

SummaryViscosification of carbon dioxide by polymers can make large scale CO2 sequestration safe and efficient. We present solubility of branched hydrocarbon oligomers in CO2 and viscosification measurements at relevant subsurface conditions. Polymers of 1-decene (P1D) with about 20 repeating units are found to be effective in CO2 viscosification, increasing it by 6.5-fold at 1.8 wt% concentration at 308 K and 31 MPa. We reason that methyl groups and branching promote solubility and viscosification. Low molecular weight oligomers can have lower solubility in CO2 than higher molecular weight ones and the trend in solubility is non-monotonic at constant pressure and temperature. Analysis of solubility trend of P1D oligomers in CO2 advances our understanding of molecular structure and functionality and opens the path to engineering of oligomers effective in viscosification and widespread use of CO2.

Living Aqueous Microemulsion Polymerization of Ethylene with Robust Ni(II) Phosphinophenolato Catalysts.

Due to chain transfer events being competitive with chain growth, ethylene polymerization by P,O-chelated Ni(II) complexes usually affords low molecular weight polymers or oligomers. We now show that appropriately bulky substituted phosphinophenolato Ni(II) can polymerize in a living fashion, virtually devoid of chain transfer. Aqueous polymerizations with microemulsions of [κ2-P,O-2-(2-(2',6'-(MeO)2C6H3)C6H4)(Ph)P-6-(3',5'-(CF3)2C6H3)C6H3O-NiMe(pyridine)] (3) at 30 °C yield polyethylenes with narrow molecular weight distributions (Mw/Mn 1.02 to 1.34) and ultrahigh molecular weights (up to 2 × 106) in the form of aqueous nanoparticle dispersions. Catalyst stability and activity are maintained up to 70 °C in water.

First report of Schiff-base nickel nanoparticle-catalyzed oligomerization and polymerization of norbornene

Ten novel Schiff-base functionalized nickel nano-systems were synthesized to investigate the capping ability of the ligands as well as the stability of the resulting nanoparticles. All four ligands employed were found to be capable and comparable stabilizers to produce monodispersed nanoparticles. These nanoparticles were further evaluated as catalysts in the polymerization of norbornene, using MAO or MMAO as a co-catalyst. All ten nanomaterials were active polymerization catalysts, resulting in the first ever reported nanoparticle-assisted polymerization processes. It was shown that the nano-catalyst can facilitate either oligomerization or polymerization depending on the co-catalyst employed. Other than vinyl polynorbornene, hydroxy functionalized oligomer stabilized nanocomposite products were also obtained. The oligomers could be cleaved from the nanoparticle surface, depending on its intended application. The vinyl polymers obtained gave high molecular weights and low polydispersity indices, whereas the hydroxy oligomers gave low molecular weight oligomers that were monodispersed. It was shown that the metal to ligand concentration, i.e. the extent of the nanoparticle surface stabilization, has little influence on the catalytic activity but rather influenced the polymer selectivity. A higher ligand to metal ratio resulted in higher molecular weight polymers with lower polydispersity indices compared to the lower metal to ligand ratio analogues. The effect of the type of ligand employed, is also investigated.

A comparative investigation of toxicity of three polymer nanoparticles on acorn barnacle (Amphibalanus amphitrite)

Pollution from plastic waste is increasingly prevalent in the environment and beginning to generate significant adverse impact on the health of living organisms. In this study, we investigate the toxicity of polymer nanoparticles exposed to Acorn Barnacle (Amphibalanus amphitrite) nauplii, as an animal model. Highly stable aqueous dispersion of luminescent nanoparticles from three common polymers: polymethylmethacrylate (PMMA), polystyrene (PS), and polyvinylchloride (PVC), were prepared via nanoprecipitation and fully characterised. Exposure studies of these polymer particles to freshly spawned barnacle nauplii were performed within a concentration range from 1 to 25 mg/L under laboratory-controlled conditions. The exposure to PMMA and PS nanoparticles did not show detrimental toxicity and did not cause sufficient mortality to compute a LC50 value. However, PVC nanoparticles were significantly toxic with a mortality rate of up to 99% at 25 mg/L, and the calculated LC50 value for PVC nanoparticles was 7.66 ± 0.03 mg/L, 95% CI. Interestingly, PVC nanoparticle aggregates were observed to adhere to the naupliar carapace and appendages at higher concentrations and could not be easily removed by washings. To explore the possibility of chemical toxicity of polymer nanoparticles, analysis of the polymer powders which was used to prepare the nanoparticles was conducted. The presence of low molecular weight oligomers such as dimers, trimers and tetramers were observed in all polymer samples. The chemical nature and concentration of such compounds are likely responsible for the observed toxicity to the barnacle nauplii. Overall, our study shows that care should be exercised in generalising the findings of exposure studies performed using one type of plastic particles, as the use of different plastic particles may elicit different responses inside a living organism.

Beyond PEO: New Polymer Electrolytes for Safe All Solid-State Lithium Metal Batteries

In a world with a growing demand in high energy storage systems and the challenge of finding new green energy sources to replace the excessively used fossil fuels, electrochemical energy storage arises as the key alternative to meet the needs of current society. In particular, lithium batteries stand out among all the available energy-storage technologies. For the last two decades, lithium-ion batteries (LIBs) have become the dominative components in portable electronic devices. However, the insufficient energy density of the state of art of LIBs has tipped the scale in favor of the search of all solid-state lithium metal (Lio) batteries (ASSLMBs) where a higher energy density can be achieved due to the high specific capacity provided by Lio electrode.As one of the most critical components, the choice of the electrolyte plays a pivotal role for preparing safe and high performance LMBs. Most of the commercial lithium batteries are built up with liquid electrolytes, which entails potential security risks such as volatilization, flammability and explosion. For this reason, numerous research efforts are focused on the obtaining of solvent-free solid electrolytes. Solid polymer electrolytes (SPEs) are considered as one of the most viable solutions to replace their liquid counterparts. In addition to the excellent flexibility, ease of processing and low cost, SPEs can mitigate the Li dendrite growth that takes place in conventional liquid electrolytes, attenuate the interfacial resistance, and improve the electrode-electrolyte compatibility compared to their inorganic counterparts.Among all the existing polymer hosts for SPEs, poly(ethylene oxide) (PEO) is the most commonly used one due to its strong solvation ability that facilitates the dissociation of various lithium salts. However, PEO lacks some essential requirements when considering it as an ideal host material for SPE; namely the low Li-ion conductivity at ambient temperature due to its crystalline nature. Thus, the low Li-ion conductivity of SPEs at ambient temperature remains as the major hindrance towards the practical deployment of lithium polymer batteries.1, 2 In order to overcome this drawback, tremendous efforts have been dedicated to the design and synthesis of new polymeric matrices that allow obtaining SPEs with improved ionic conductivity at room temperature, where modification such as cross-linking or copolymerization, or the use of low molecular weight oligomers are the main used strategies. In addition, the anion concentration gradient that takes place in conventional dual-ion conductors is one of the factors responsible for low Li-ion transference number (T Li + < 0.5) and consequently are more susceptible to polarization phenomena that eventually limit the power density and cycle life of lithium batteries. The main strategy to go through this polarization problem is the development of single lithium-ion conducting solid polymer electrolytes (SLIC-SPEs), where the anion is immobilized by different means.3 Inspired by previously stated challenges, in the present work we will present the performance of novel flexible and highly conductive SPEs in order to decrease the working temperature. Moreover, the role of different additives on the performance of new SLIC-SPEs is provided.