Polymer Migration Research Articles

A comprehensive risk assessment of microplastics in soil, water, and atmosphere: Implications for human health and environmental safety

Microplastics (MPs) are pervasive across ecosystems, likely posing significant environmental and health risks based on more and more evidence. In this study, we searched through the Web of Science Core Collection and obtained 1039 papers for visualization and analysis. In order to discuss the chemical composition, migration, transformation and potential risk of MPs, 135 sets of relevant data in soil, water, and atmosphere were collected in China as a typical region, which is a hotspot region for investigation of MPs. The results showed that the primary polymer categories of MPs in the environment to be polypropylene, polyethylene, and polystyrene. The soil contains a significant quantity of MPs, averaging at 12,107.42 items·kgdw−1, while water contains averaging at 97,271.18 items m−3. The total pollution load indexes for all three environments are at risk level I. Based on current risk assessment methods, the potential ecological risk of MPs is low. However, based on the polymer components, migration and transformation patterns, and especially the complexes with other pollutants, it indicates an increasing indirect risk. Interactions with some other pollutants are likely amplify the ecological and health risks associated with MPs. Aggregative results showed that the present risk assessment models could not assess the risks of MPs well. Thus, we suggested develop a risk assessment methodology for MPs based on relevant research progress. Some factors such as the size and form of MPs, sources and distribution, bioaccumulation, social acceptance and economic costs could be considered adding in the present risk assessment models. Finally, promotion of development and application of green chemically synthesized bioplastics such as using synthetic biology to help degrade plastics would be an alternative and sustainable option to relieve the adverse environmental and health concerns of MPs.

Migration and Separation of Polymers in Nonuniform Active Baths.

Polymerlike structures are ubiquitous in nature and synthetic materials. Their configurational and migration properties are often affected by crowded environments leading to nonthermal fluctuations. Here, we study an ideal Rouse chain in contact with a nonhomogeneous active bath, characterized by the presence of active self-propelled agents which exert time-correlated forces on the chain. By means of a coarse-graining procedure, we derive an effective evolution for the center of mass of the chain and show its tendency to migrate toward and preferentially localize in regions of high and low bath activity depending on the model parameters. In particular, we demonstrate that an active bath with nonuniform activity can be used to separate efficiently polymeric species with different lengths and/or connectivity.

Chemical stability of anion exchange membranes for alkaline fuel cells and water electrolysers: Experiment, multi-dimensional modeling and hybrid simulations

The unstable nature of anion exchange membranes (AEMs) has hindered the progress of alkaline fuel cells and water electrolyzers. Density functional theory (DFT) can explore the correlation between the structure and properties of model compounds. However, theoretical explorations of AEMs remain immensely insufficient owing to the complexity of modeling the realistic solution system which caused by multi-dimensional parameters such as polymer chain entanglement, steric hindrance, and migration of ions. In this study, molecular dynamic simulation was utilized to obtain the multi-dimensional parameters of polyelectrolytes, which were considered when calculating the degradation energy barrier by DFT, thus leading to more accurate results and optimizing the conventional DFT calculations. Combined with the computational works, pyridinium functionalized polyolefin and polyether sulfone were synthesized to verify the feasibility of the simulation scheme. This optimized scheme fills the gap in the DFT calculations scale and is easy to extend to other types of AEMs, which help design the chemically stable AEMs and promote the development of alkaline fuel cells and water electrolysers.

Adsorption characteristics and mechanisms of water-soluble polymers (PVP and PEG) on kaolin and montmorillonite minerals

The excessive use and accumulation of water-soluble polymers (WSPs, known as “liquid plastics”) in the environment can pose potential risks to both ecosystems and human health, but the environmental fate of WSPs remains unclear. Here, the adsorption behavior of WSPs with different molecular weight on kaolinite (Kaol) and montmorillonite (Mt) were examined. The results showed that the adsorption of PEG and PVP on minerals were controlled by hydrogen bond and van der Waals force. The Fourier transform infrared (FTIR) spectra and two-dimensional correlation spectroscopy (2D-COS) analysis revealed that there were interactions between the Al-O and Si-O groups of the minerals and the polar O- or N-containing functional groups as well as the alkyl groups of PEG and PVP. The adsorption characteristics of WSPs were closely related to their molecular weight and the pore size of minerals. Due to the relatively large mesopore size of Kaol, both PEG and PVP were absorbed into inner spaces, for which the adsorption capacity increased with molecular weight of the polymers. For Mt, all types of PEG could enter its micropores, while PVP with larger molecular weights appeared to be confined externally, leading to a decrease in the adsorption capacity of PVP with increasing molecular weight. The findings of this study provide a theoretical basis for scientific evaluation of environmental processes of WSPs.

Molecular Engineering of Perylene Diimide Polymers with a Robust Built-in Electric Field for Enhanced Solar-Driven Water Splitting.

The built-in electric field of the polymer semiconductors could be regulated by the dipole moment of its building blocks, thereby promoting the separation of photogenerated carriers and achieving efficient solar-driven water splitting. Herein, three perylene diimide (PDI) polymers, namely oPDI, mPDI and pPDI, are synthesized with different phenylenediamine linkers. Notably, the energy level structure, light-harvesting efficiency, and photogenerated carrier separation and migration of polymers are regulated by the orientation of PDI unit. Among them, oPDI enables a large dipole moment and robust built-in electric field, resulting in enhanced solar-driven water splitting performance. Under simulated sunlight irradiation, oPDI exhibits the highest photocurrent of 115.1 μA cm-2 for photoelectrochemical oxygen evolution, which is 11.5 times that of mPDI, 26.8 times that of pPDI and 104.6 times that of its counterparts PDI monomer at the same conditions. This work provides a strategy for designing polymers by regulating the orientation of structural units to construct efficient solar energy conversion systems.

Molecular Engineering of Perylene Diimide Polymers with a Robust Built‐in Electric Field for Enhanced Solar‐Driven Water Splitting

AbstractThe built‐in electric field of the polymer semiconductors could be regulated by the dipole moment of its building blocks, thereby promoting the separation of photogenerated carriers and achieving efficient solar‐driven water splitting. Herein, three perylene diimide (PDI) polymers, namely oPDI, mPDI and pPDI, are synthesized with different phenylenediamine linkers. Notably, the energy level structure, light‐harvesting efficiency, and photogenerated carrier separation and migration of polymers are regulated by the orientation of PDI unit. Among them, oPDI enables a large dipole moment and robust built‐in electric field, resulting in enhanced solar‐driven water splitting performance. Under simulated sunlight irradiation, oPDI exhibits the highest photocurrent of 115.1 μA cm−2 for photoelectrochemical oxygen evolution, which is 11.5 times that of mPDI, 26.8 times that of pPDI and 104.6 times that of its counterparts PDI monomer at the same conditions. This work provides a strategy for designing polymers by regulating the orientation of structural units to construct efficient solar energy conversion systems.

Active motion of tangentially driven polymers in periodic array of obstacles

One key question about transport of active polymers within crowded environments is how spatial order of obstacles influences their conformation and dynamics when compared to disordered media. To this end, we computationally investigate the active transport of tangentially driven polymers with varying degrees of flexibility and activity in two-dimensional square lattices of obstacles. Tight periodic confinement induces notable conformational changes and distinct modes of transport for flexible and stiff active filaments. It leads to caging of low activity flexible polymers inside the inter-obstacle pores while promoting more elongated conformations and enhanced diffusion for stiff polymers at low to moderate activity levels. The migration of flexible active polymers occurs via hopping events, where they unfold to move from one cage to another, similar to their transport in disordered media. However, in ordered media, polymers are more compact and their long-time dynamics is significantly slower. In contrast, stiff chains travel mainly in straight paths within periodic inter-obstacle channels while occasionally changing their direction of motion. This mode of transport is unique to periodic environment and leads to more extended conformation and substantially enhanced long-time dynamics of stiff filaments with low to moderate activity levels compared to disordered media. At high active forces, polymers overcome confinement effects and move through inter-obstacle pores just as swiftly as in open spaces, regardless of the spatial arrangement of obstacles. We explain the center of mass dynamics of semiflexible polymers in terms of active force and obstacle packing fraction by developing an approximate analytical theory.

Mechanistic Insights into a Novel Controllable Phase-Transition Polymer for Enhanced Oil Recovery in Mature Waterflooding Reservoirs.

Expanding swept volume technology via continuous-phase polymer solution and dispersed-phase particle gel is an important technique to increase oil production and control water production in mature waterflooding reservoirs. However, problems such as the low viscosity retention rate, deep migration, and weak mobility control of conventional polymers, and the contradiction between migration distance of particle gel and plugging strength, restrict the long-term effectiveness of oil displacement agents and the in-depth sweep efficiency expanding capability in reservoirs. Combined with the technical advantages of polymer and particle gel, a novel controllable phase-transition polymer was developed and systematically studied to gain mechanistic insights into enhanced oil recovery for mature waterflooding reservoirs. To reveal the phase-transition mechanism, the molecular structure, morphology, and rheological properties of the controllable phase-transition polymer were characterized before and after phase transition. The propagation behavior of the controllable phase-transition polymer in porous media was studied by conducting long core flow experiments. Two-dimensional micro visualization and parallel core flooding experiments were performed to investigate the EOR mechanism from porous media to pore level. Results show that the controllable phase-transition polymer could change phase from dispersed-phase particle gel to continuous-phase solution with the prolongation of ageing time. The controllable phase-transition polymer exhibited phase-transition behavior and good propagation capability in porous media. The results of micro visualization flooding experiments showed that the incremental oil recovery of the controllable phase-transition polymer was highest when a particle gel and polymer solution coexisted, followed by a pure continuous-phase polymer solution and pure dispersed-phase particle gel suspension. The recovery rate of the novel controllable phase-transition polymer was 27.2% after waterflooding, which was 8.9% higher than that of conventional polymer, providing a promising candidate for oilfield application.

Cooking food in microwavable plastic containers: in situ formation of a new chemical substance and increased migration of polypropylene polymers.

Microwavable plastic food containers can be a source of toxic substances. Plastic materials such as polypropylene polymers are typically employed as safe materials in food packaging, but recent research demonstrates the migration of plastic substances or their by-products to food simulants, to foodstuff, and, more recently, to the human body through food consumption. However, a thorough evaluation of foodstuff in food contact materials under cooking conditions has not yet been undertaken. Here we show for the first time that plastic migrants present in food contact materials can react with natural food components resulting in a compound that combines a UV-photoinitiator (2-hydroxy-2-methyl-1-phenylpropan-1-one) with maltose from potato starch; this has been identified after cooking potatoes in microwavable plastic food containers. Additionally, polypropylene glycol substances have been found to transfer into food through microwave cooking. Identifying these substances formed in situ requires state-of-the-art high-resolution mass spectrometry instrumentation and metabolomics-based strategies.

Preparation and Characterization of a Janus Membrane with an “Integrated” Structure and Adjustable Hydrophilic Layer Thickness

Oil-water emulsions are types of wastewater that are difficult to treat. A polyvinylidene fluoride hydrophobic matrix membrane was modified using a hydrophilic polymer, poly(vinylpyrrolidone-vinyltriethoxysilane), to form a representative Janus membrane with asymmetric wettability. The performance parameters of the modified membrane, such as the morphological structure, the chemical composition, the wettability, the hydrophilic layer thickness, and the porosity, were characterized. The results showed that the hydrolysis, migration, and thermal crosslinking of the hydrophilic polymer in the hydrophobic matrix membrane contributed to an effective hydrophilic layer on the surface. Thus, a Janus membrane with unchanged membrane porosity, a hydrophilic layer with controllable thickness, and hydrophilic/hydrophobic layer "structural integration" was successfully prepared. The Janus membrane was used for the switchable separation of oil-water emulsions. The separation flux of the oil-in-water emulsions on the hydrophilic surface was 22.88 L·m-2·h-1 with a separation efficiency of up to 93.35%. The hydrophobic surface exhibited a separation flux of 17.45 L·m-2·h-1 with a separation efficiency of 91.47% for the water-in-oil emulsions. Compared to the lower flux and separation efficiency of purely hydrophobic and hydrophilic membranes, the Janus membrane exhibited better separation and purification effects for both oil-water emulsions.

A constant current triboelectric nanogenerator achieved by hysteretic and ordered charge migration in dielectric polymers

Utilizing the hysteretic and ordered charge migration behavior of dielectric polymers, a new concept of constant current triboelectric nanogenerators is proposed.

Enhancement of single upconversion nanoparticle imaging by topologically segregated core-shell structure with inward energy migration

Manipulating topological arrangement is a powerful tool for tuning energy migration in natural photosynthetic proteins and artificial polymers. Here, we report an inorganic optical nanosystem composed of NaErF4 and NaYbF4, in which topological arrangement enhanced upconversion luminescence. Three architectures are designed for considerations pertaining to energy migration and energy transfer within nanoparticles: outside-in, inside-out, and local energy transfer. The outside-in architecture produces the maximum upconversion luminescence, around 6-times brighter than that of the inside-out at the single-particle level. Monte Carlo simulation suggests a topology-dependent energy migration favoring the upconversion luminescence of outside-in structure. The optimized outside-in structure shows more than an order of magnitude enhancement of upconversion brightness compared to the conventional core-shell structure at the single-particle level and is used for long-term single-particle tracking in living cells. Our findings enable rational nanoprobe engineering for single-molecule imaging and also reveal counter-intuitive relationships between upconversion nanoparticle structure and optical properties.

Migration of active rings in porous media.

Inspired by how the shape deformations in active organisms help them to migrate through disordered porous environments, we simulate active ring polymers in two-dimensional random porous media. Flexible and inextensible active ring polymers navigate smoothly through the disordered media. In contrast, semiflexible rings undergo transient trapping inside the pore space; the degree of trapping is inversely correlated with the increase in activity. We discover that flexible rings swell while inextensible and semiflexible rings monotonically shrink upon increasing the activity. Together, our findings identify the optimal migration of active ring polymers through porous media.

Mesoscopic simulations of inertial drag enhancement and polymer migration in viscoelastic solutions flowing around a confined array of cylinders

We study the flow around a periodic array of cylinders using a mesoscopic viscoelastic fluid that mimics polymeric solutions. We model our fluid employing a novel mesoscopic method based on Smoothed Dissipative Particle Dynamics and FENE springs. We characterize the static and dynamic properties of our model solutions and compare the results with theoretical predictions based on the Zimm model. After rheological characterization of the modeled solutions, we simulate the flow around a confined array of cylinders. The balance between inertia and elasticity in our simulations is studied using a wide range of Reynolds (Re) and Weissenberg (Wi) numbers. We find that increasing the flow rate reduces the drag coefficient on the cylinder up to a critical Re corresponding to a minimum. Thereafter, inertia becomes dominant and we encounter drag enhancement for all the solutions studied, including the Newtonian solvent. With the use of simple model for the viscous and inertial contributions to drag, we conclude that inertial effects are driving the increase in the drag experienced by the cylinder. In our simulations, we also observe migration of polymer chains away from the channel walls and in the wake of the cylinder. We conclude that stress gradients induced by the curvature of streamlines and convection of the depleted layers at the walls as the principal mechanisms driving the migration of chains. We find the extent of the migration correlates well with the viscoelastic Mach number (Ma = Re Wi ) suggesting that both elastic and inertial effects play a role in this phenomenon. • A mesoscopic model fluid with viscoelastic behavior is presented. • The drag on a confined array of periodically spaced cylinders is investigated. • Drag enhancement is explained with a simple model combining inertial and viscous drag. • Polymeric migration at the walls and the wake of the cylinders is investigated.

Phase Field Modeling on By-Product Migration in Crosslinking Polymers for HVDC Cable Insulation Applications

Cross-linking by-products has been considered as one of the crucial factors for dielectric properties of cross-linked polyethylene, which plays an important role in the insulation performance of high voltage direct current (HVDC) cables. It migrates across cable insulation incorporating space charge effect, temperature variation of conductivity, etc., which makes it a long-standing puzzle of manipulating the electric field distribution for HVDC cable insulation, especially with the increasing voltage level. Nevertheless, there still lacks a theoretical model describing the migration of the by-products, especially for cable insulation with sizeable dimensions. In this article, a phase field model is established to simulate the migration of acetophenone (i.e., one of the by-products) through calculating the free energy landscape considering the competition between the diffusion driven by concentration gradient and the uphill diffusion caused by by-product aggregation. The results show that the time-dependence migration during degassing leads to an uneven distribution of acetophenone across the cable insulation, which is in good coincidence with the measured results for a full-size cable. Accordingly, the distortion of the electric field in HVDC cable insulation due to the radial distribution variation of acetophenone has been estimated regarding the relationship between by-product content and conductivity, and a method of manipulating the distribution of acetophenone is proposed to optimize the distribution of the electric field in cable insulation. Our work provides a numerical approach for the simulation of by-product migration in crosslinked polymers for insulation applications.

Tuning adhesion performance of an acrylic pressure‐sensitive adhesive using polysilsesquioxane‐acrylic core‐shell nanoparticles

AbstractSurface migration of unmodified inorganic or polymer core‐inorganic shell nanoparticles has limited their application for improvement of pressure‐sensitive adhesives (PSAs) properties. The efficiency of utilization of modified inorganic nanoparticles with sticky polymer brushes was investigated to overcome this problem. For this purpose, polymethacryloxypropylsilsesquioxane‐acrylic core‐shell (CS) nanoparticles were synthesized and added to poly(methyl methacrylate‐co‐butyl acrylate) (MBC) acrylic PSA through latex blending. Using CS nanoparticles, a concomitant increase in the peel and shear strengths of the acrylic PSA was achieved, and also the limitation of surface migration of nanoparticles at high volume fractions was overcome. Moreover, CS nanoparticles acted as a compatibilizer for MBC chains, rich in methyl methacrylate (MMA) or butyl acrylate (BA). These MMA‐rich and BA‐rich chains were formed during the synthesis of MBC latex through batch emulsion copolymerization method, due to the difference in the reactivity ratio of BA and MMA radicals. The compatibility of CS nanoparticles with each of the components of MBC was systematically investigated in terms of grafting density, swelling ratio, and thermodynamic affinity and was correlated to the final properties.

Predictions of polymer migration in a dilute solution between rotating eccentric cylinders

Our recent continuum theory for stress-gradient-induced migration of polymers in confined solutions, including the depletion from the solid boundaries [Hajizadeh, E., and R. G. Larson, Soft Matter, 13, 5942–5949 (2017)], is applied to a two-dimensional rotational shearing flow in the gap between eccentric cylinders. Analytical results for the steady-state distribution of polymer dumbbells in the limit of dilute polymer solution c/c∗≪1 (c∗ is the chain overlap concentration) and in the absence of hydrodynamic interactions are obtained. The effects of eccentricity e and of three perturbation variables, namely, Weissenberg number Wi, gradient number Gd(which defines the level of polymer chain confinement), and Péclet number Pe on the polymer concentration pattern, are investigated. The stress-gradient-induced migration results in polymer migration toward the inner cylinder, while wall-depletion-induced migration results in near-zero polymer concentration close to flow boundaries, which couples to a stress-gradient-induced migration effect. In the presence of wall-depletion, we obtain first order concentration variation proportional to Wi. However, in the absence of wall-depletion, there is no first order contribution and, therefore, the lowest-order concentration variation is proportional to Wi2. An upper limit of Wi=1.6 exists, beyond which the numerical solution demands an excessive under-relaxation to converge. In addition, for a high degree of polymer chain confinement, i.e., for Gd greater than 0.5, the continuum theory fails to be accurate and mesoscopic simulations that track individual polymer molecules are needed.

Migration of liquid silicone, an emerging contraindication of neuraxial anesthesia

The illegal use of liquid silicone products or biopolymers in gluteal augmentation procedures is giving rise to multiple complications, with a significant negative health impact, both in the short and long-term. The migration of polymers to the sacral and lumbar region represents a major limitation to conducting neuraxial anesthesia procedures. This silicon migration is unpredictable through the superficial tissue as is widely described in the literature. Caudal, spinal and epidural anesthesia may cross the silicone in the fascia and contaminate the neural axis with substances that are highly capable of causing inflammation, edema and tissue necrosis. In order to improve the safety of neuraxial anesthetic procedures and avoid the potential risk of dissemination and contamination of the neural axis, this complication must be ruled out, or be considered an emerging contraindication for these anesthetic procedures.

Angle‐Independent Structurally Colored Materials with Superhydrophobicity and Self‐Healing Capability

AbstractBioinspired structurally colored materials with superwettability have aroused considerable interest, but it is still a formidable challenge to produce large‐scale superhydrophobic photonic materials with high mechanical durability. Herein, a superhydrophobic photonic composite with angle‐independent structural colors and self‐healing capability is reported, by embedding photonic glass on a healable supramolecular polymer with hydrophobic polydimethylsiloxane segments. Superhydrophobicity of the composite originates from the migration of the supramolecular polymer around the photonic glass pigments with micro–nano structure. This superhydrophobic characteristic has long‐term stability that can maintain for months. Based on the self‐cleaning property, nonwettability and vivid angle‐independent structural colors, the composite can be applied as large‐area antifouling and coloring coatings. Moreover, the reversible hydrogen bonds endow the composite with self‐healing ability and mechanical durability properties, which is crucial to practical applications as biomimetic decorative materials and wearable devices.

Understanding the Polymer Rearrangement of pH-Responsive Nanoparticles

The use of self-assembled nanoparticles for drug delivery has received significant attention in recent years. However, the dynamic nature of self-assembled polymeric systems means there is a need to develop greater understanding of the inherent stability of these systems. In particular, understanding if these materials remain as discrete nanoparticles, or if there is dynamic exchange of material between particles is critical. Herein, we labelled pH-responsive nanoparticles with fluorescent dyes and then investigated the change in fluorescence when the particles were mixed with unlabelled nanoparticles in order to investigate their potential for polymer rearrangement. Nanoparticles were formed by the nanoprecipitation of pH-responsive poly(ethylene glycol)-block-poly(2-(diethylamino)ethyl methacrylate) (PEG-b-PDEAEMA) as the shell and poly(2-(diethylamino)ethyl methacrylate)-random-poly(2-(diisopropylamino)ethyl methacrylate) (PDEAEMA-r-PDPAEMA) as the core. The core and shell were labelled by incorporating pentafluorophenyl methacrylate (PFPMA) in core or shell respectively and then coupling with either Sulfo-cyanine5 amine or Cyanine3 amine. Exchange of material between nanoparticles was probed by tracking changes in the self-quenching of fluorescently labelled polymers in the core of the nanoparticles. The fluorescence intensity of the labelled nanoparticles was stable when mixed with unlabelled nanoparticles at physiological pH (pH 7.4), suggesting there is limited migration of polymers between particles in this system. This study provides important insights into the use of non-crosslinked nanoparticles under biologically relevant conditions.