Entangled Polymer Chains Research Articles

End‐Extended Conjugation Strategy to Reduce the Efficiency‐Stability‐Mechanical Robustness Gap in Binary All‐Polymer Solar Cells

AbstractConcurrently achieving high efficiency, mechanical robustness and thermal stability is critical for the commercialization of all‐polymer solar cells (APSCs). However, APSCs usually demonstrate complicated morphology, primarily attributed to the polymer chain entanglement which has a detrimental effect on their fill factors (FF) and morphology stability. To address these concerns, an end‐group extended polymer acceptor, PY‐NFT, was synthesized and studied. The morphology analysis showed a tightly ordered molecular packing mode and a favorable phase separation was formed. The PM6 : PY‐NFT‐based device achieved an exceptional PCE of 19.12 % (certified as 18.45 %), outperforming the control PM6 : PY‐FT devices (17.14 %). This significant improvement highlights the record‐high PCE for binary APSCs. The thermal aging study revealed that the PM6 : PY‐NFT blend exhibited excellent morphological stability, thereby achieving superior device stability, retaining 90 % of initial efficiency after enduring thermal stress (65 °C) for 1500 hours. More importantly, the PM6 : PY‐NFT blend film exhibited outstanding mechanical ductility with a crack onset strain of 24.1 %. Overall, rational chemical structure innovation, especially the conjugation extension strategy to trigger appropriate phase separation and stable morphology, is the key to achieving high efficiency, improved thermal stability and robust mechanical stability of APSCs.

Tailoring the Mechanical Properties and Foaming Behaviors of PLA/P4HB Blends by Using P4HB‐g‐GMA as Compatibilizer

ABSTRACTSynthetic poly(4‐hydroxybutyrate) (P4HB), a flexible and biodegradable polymer, shows great promise in improving the toughness of poly(lactic acid) (PLA), but the inherent immiscibility of PLA and P4HB compromises the toughening efficiency. To address this issue, P4HB grafted glycidyl methacrylate (P4HB‐g‐GMA) is synthesized for the purpose of enhancing the compatibility within the PLA/P4HB blend. The epoxy groups on P4HB‐g‐GMA can form strong chemical bonds with PLA chains and remain compatible with P4HB. Rheological data confirm that adding P4HB‐g‐GMA enhances polymer chain entanglement. Therefore, the phase interface of the blend becomes more diffuse, leading to improved mechanical performance. Specifically, a 3D‐printed PLA/P4HB/P4HB‐g‐GMA blend containing 8% P4HB‐g‐GMA (PLA/P4HB/G8) achieves an elongation at break of 161.5%, approximately 22.7 times higher than that of a PLA/P4HB blend without the modifier. Moreover, the PLA/P4HB/G8 blends show a higher volume expansion ratio (VER) and better cell morphology due to the increased melt strength from P4HB‐g‐GMA. This study demonstrates a simple and efficient method to improve the compatibility between PLA and P4HB, resulting in superior mechanical performance of PLA/P4HB blends and broadening their potential applications in foaming.

Asymmetrified Benzothiadiazole‐Based Solid Additives Enable All‐Polymer Solar Cells with Efficiency Over 19 %

AbstractDisordered polymer chain entanglements within all‐polymer blends limit the formation of optimal donor‐acceptor phase separation. Therefore, developing effective methods to regulate morphology evolution is crucial for achieving optimal morphological features in all‐polymer organic solar cells (APSCs). In this study, two isomers, 4,5‐difluorobenzo‐c‐1,2,5‐thiadiazole (SF‐1) and 5,6‐difluorobenzo‐c‐1,2,5‐thiadiazole (SF‐2), were designed as solid additives based on the widely‐used electron‐deficient benzothiadiazole unit in nonfullerene acceptors. The incorporation of SF‐1 or SF‐2 into PM6 : PY‐DT blend induces stronger molecular packing via molecular interaction, leading to the formation of continuous interpenetrated networks with suitable phase‐separation and vertical distribution. Furthermore, after treatment with SF‐1 and SF‐2, the exciton diffusion lengths for PY‐DT films are extended to over 40 nm, favoring exciton diffusion and charge transport. The asymmetrical SF‐2, characterized by an enhanced dipole moment, increases the power conversion efficiency (PCE) of PM6 : PY‐DT‐based device to 18.83 % due to stronger electrostatic interactions. Moreover, a ternary device strategy boosts the PCE of SF‐2‐treated APSC to over 19 %. This work not only demonstrates one of the best performances of APSCs but also offers an effective approach to manipulate the morphology of all‐polymer blends using rational‐designed solid additives.

Asymmetrified Benzothiadiazole-Based Solid Additives Enable All-Polymer Solar Cells with Efficiency Over 19 .

Disordered polymer chain entanglements within all-polymer blends limit the formation of optimal donor-acceptor phase separation. Therefore, developing effective methods to regulate morphology evolution is crucial for achieving optimal morphological features in all-polymer organic solar cells (APSCs). In this study, two isomers, 4,5-difluorobenzo-c-1,2,5-thiadiazole (SF-1) and 5,6-difluorobenzo-c-1,2,5-thiadiazole (SF-2), were designed as solid additives based on the widely-used electron-deficient benzothiadiazole unit in nonfullerene acceptors. The incorporation of SF-1 or SF-2 into PM6 : PY-DT blend induces stronger molecular packing via molecular interaction, leading to the formation of continuous interpenetrated networks with suitable phase-separation and vertical distribution. Furthermore, after treatment with SF-1 and SF-2, the exciton diffusion lengths for PY-DT films are extended to over 40 nm, favoring exciton diffusion and charge transport. The asymmetrical SF-2, characterized by an enhanced dipole moment, increases the power conversion efficiency (PCE) of PM6 : PY-DT-based device to 18.83 % due to stronger electrostatic interactions. Moreover, a ternary device strategy boosts the PCE of SF-2-treated APSC to over 19 %. This work not only demonstrates one of the best performances of APSCs but also offers an effective approach to manipulate the morphology of all-polymer blends using rational-designed solid additives.

End-Extended Conjugation Strategy to Reduce the Efficiency-Stability-Mechanical Robustness Gap in Binary All-Polymer Solar Cells.

Concurrently achieving high efficiency, mechanical robustness and thermal stability is critical for the commercialization of all-polymer solar cells (APSCs). However, APSCs usually demonstrate complicated morphology, primarily attributed to the polymer chain entanglement which has a detrimental effect on their fill factors (FF) and morphology stability. To address these concerns, an end-group extended polymer acceptor, PY-NFT, was synthesized and studied. The morphology analysis showed a tightly ordered molecular packing mode and a favorable phase separation was formed. The PM6 : PY-NFT-based device achieved an exceptional PCE of 19.12 % (certified as 18.45 %), outperforming the control PM6 : PY-FT devices (17.14 %). This significant improvement highlights the record-high PCE for binary APSCs. The thermal aging study revealed that the PM6 : PY-NFT blend exhibited excellent morphological stability, thereby achieving superior device stability, retaining 90 % of initial efficiency after enduring thermal stress (65 °C) for 1500 hours. More importantly, the PM6 : PY-NFT blend film exhibited outstanding mechanical ductility with a crack onset strain of 24.1 %. Overall, rational chemical structure innovation, especially the conjugation extension strategy to trigger appropriate phase separation and stable morphology, is the key to achieving high efficiency, improved thermal stability and robust mechanical stability of APSCs.

Fabrication of PEI/CF composite parts with multi-angle reinforced mechanical properties by a micro-extrusion foaming FDM process

The combination of fused deposition modeling (FDM) and foaming technology enables the fabrication of complex hierarchical and lightweight parts. However, this approach is hindered by a reduction in the mechanical properties of final parts. To this end, with the aim of addressing the challenge of the fabrication of 3D-printed parts with enhanced mechanical and lightweight features, a micro-extrusion foaming FDM process using CO2 as a blowing agent was hereby established, and the carbon fiber (CF) was selected as a reinforcing filler. Compared to pure polyetherimide (PEI) parts, the longitudinal tensile strength of the PEI/CF parts with 5.0 wt% CF added increased by 30.3 %, while the interfacial bonding strength of PEI/CF-5.0 foamed parts increased by 86.3 % compared to the unfoamed parts. Furthermore, the PEI/CF-5.0 foamed parts, weighing only about 1.7 g, could bear a load of a 60 kg human body in multiple directions. Additionally, focusing on the filler orientation and the enhanced interdiffusion and entanglement of polymer chains at interfaces, the reinforcement mechanisms of the foamed parts fabricated by micro-extrusion foaming FDM process were discussed. The micro-extrusion foaming FDM process demonstrated the capability to produce lightweight parts with enhanced mechanical properties, making it a promising technology for applications in the aerospace and military industries.

Effect of Phase Structure on the Viscoelasticity and Mechanical Properties of Isotactic Polypropylene Multicomponents Polymerized with Non-Conjugated α,ω-Diene.

Increasing of rubber content in isotactic polypropylene/ethylene-propylene rubber (iPP/EPR) alloys can extend the applications of this kind of polyolefin. The EPR content and phase structure of isotactic polypropylene multicomponents have great effect on the viscoelasticity and mechanical properties. iPP/EPR in-reactor alloys with a high EPR content were obtained through the in situ crosslinking of EPR chains with α,ω-diene. The morphological observation results indicate that the crosslinked iPP/EPR in-reactor alloys have a good spherical shape with clean and rough external surfaces. The high EPR content is finely dispersed in the crosslinked iPP/EPR alloys in areas ranging in size from tens of nanometers to several micrometers, which implies that a sufficient crosslinking degree of EPR chains can effectively prevent their aggregation and restrict macro-phase separation. The rheological results show a clear plateau in the terminal region, which reveals an entangled polymer chain network in the crosslinked iPP/EPR alloys. The well-dispersed EPR and the bi-continuous phase structure have a great effect on the mechanical properties of the isotactic polypropylene multicomponent which were assessed.

Fabrication of ultrafiltration membranes based on methacrylate copolymers containing quaternary ammonium and PEG units for dye removal

Abstract Phase inversion involves in a complex process due to numerous factors affecting the membrane formation. Among them, polymer chain entanglement from polymeric membrane materials plays a critical role in regulating membrane structure and is still worth further exploration. Herein, a series of methacrylate copolymers with different contents of poly(ethylene glycol) methacrylate (PEGMA) were designed and synthesized, and ultrafiltration membranes cast from these copolymers were systematically investigated regarding structural evolution and filtration performance. Surface zeta potential of membranes gradually transformed from positive to negative with the increasing PEGMA content due to nonsolvent-induced surface migration of element oxygen, and meanwhile the transformation from finger-like pore structure to sponge-like pore structure in the support layer was observed, which could be attributed to chain entanglement of the PEGMA-rich copolymer. Filtration experiments indicated that sponge-like membranes possessed better separation effect of Victoria blue B compared with finger-like membranes, and the optimized mPP40-15 % showed a retention rate of 99.55 % and permeance of 110.26 L m−2 h−1 bar−1 and displayed good selective separation of dye/salt mixture. Besides, sponge-like membranes also exhibited easy regeneration, anti-fouling property and filtration stability. This work will provide guidance for modulating membrane structure and offer an alternative material for membrane separation in handling dye wastewater.

PREDICTIONS AND VERIFICATIONS OF UNIVERSAL COOPERATIVE RELAXATION AND DIFFUSION IN MATERIALS

ABSTRACT Since its inception in 1979, the coupling model has predictions on the dynamic properties of relaxation and diffusion that should be universal in materials with many-body interactions. The verifications of this bold prediction require studies of many different relaxation and diffusion processes in diverse kinds of material. These tasks, performed over the past four decades, have culminated in the overwhelming confirmation of the predictions as reported in my previous extensive review (Prog. Mater. Sci.139, 101130 [2023]). A large variety of relaxation and diffusion processes in widely different classes of materials are shown to have the predicted universal properties. In particular for polymers, the local segmental relaxation responsible for glass transition conforms to the universal properties. However, not known is whether diffusion of the entangled chains in high molecular weight polymers also follows the same properties. Published data of the diffusion of entangled polymer chains from experiments and simulations are reexamined and reevaluated to show indeed that they are in conformity with the universal properties. The same conclusion holds also for diffusion and rheology of entangled cyclic polymers. This paper is written as a tribute to C. Michael Roland for his scientific collaborations and camaraderie with me over many years.

Unmatched resilience and fatigue resistance in a novel cellulose-derived ionic gel with hierarchical superstructured synergy for advanced human-computer interaction

Unlike traditional hydrogels, solvent-free ionic gels eliminate leakage and solvent volatilization, making them suitable for applications in electronic skin, sensing, and other fields due to their excellent conductivity and flexibility. However, designing solvent-free ionic gels with exceptional fatigue resistance, high ionic conductivity, and toughness remains a significant challenge. We address this challenge by employing small molecule/polymer heating self-assembly to regulate the synergistic effects of various components on the hierarchical superstructure. A multi-stage network was formed through the free radical polymerization of 3-Ethyl-1-vinyl-1H-imidazol-3-ium bromide ([C2VIm]Br), lipoic acid (LA), acrylic acid (AA), and hydroxypropyl cellulose (HPC), stabilized by dense hydrogen bonding and polymer chain entanglement. The resulting HPC/LA/AA/iLs (HLAI) ionic gel exhibits exceptional properties: excellent flexibility (with an elongation at break of 4222 %), toughness (1.03 MJ/m3), high ionic conductivity (3.29 × 10−2 S/m), and outstanding fatigue resistance (with a resilience of 91.9 % after 1000 load-unloading cycles at 50 % strain). Additionally, it shows low sensitivity to crack propagation (50 % notched sample can be stretched to 9 times without breaking) and good environmental stability, demonstrating excellent sensing sensitivity and stability (GF=3.23). The conductive ionic gel features a sophisticated hierarchical superstructure that synergistically enhances its properties at the molecular level. The integration of dynamic disulfide bonds, achieved through the polymerization of Lipoic acid, imparts remarkable self-healing capabilities and superior fatigue resistance. Additionally, the incorporation of a rigid HPC structure with dense cross-linking points bolsters elasticity, fracture resistance, and resilience. The gel’s ionic conductivity and sensing sensitivity are significantly enhanced by the inclusion of ionic liquids with polymerizable double bonds, making it an ideal material for applications requiring both flexibility and conductivity. This work presents a novel strategy for designing high-performance multi-stage network solvent-free ionic gels, opening up exciting possibilities for biomimetic electronic skin applications.

Hydrogels with high sacrifice efficiency of sacrificial bonds and with high strength and toughness due to dense entanglements of polymer chains

Introducing sacrificial bonds is a common method for increasing the toughness of hydrogels. Many sacrificial bonds have been extensively investigated, but the sacrifice efficiency has never been studied. In this study, polyacrylamide hydrogels with highly entangled polymer chains containing carboxyl–zirconium (–COO−–Zr4+) sacrificial bonds are prepared to study the effect of polymer chain entanglement on the sacrificial bond efficiency. Unlike chemical crosslinking points, the dense physical entanglements do not affect the toughness (∼43 MJ/m3) of hydrogels but significantly improve the tensile strength (by two times) and Young’s modulus (by six times). Physical entanglements enable the chains to slide and adjust the network structure under stress, which enables more polymer chains and sacrificial bonds to participate in the deformation process. Therefore, dense entanglements will greatly improve the sacrifice efficiency. However, a high density of chemical crosslinking points will limit the improvement in the sacrifice efficiency, which is attributed to the sliding limitations because of physical entanglement. The highly entangled polyacrylamide hydrogels toughened by –COO−–Zr4+ have an excellent load-bearing capacity. This study provides a novel strategy for designing hydrogels with ultra-high strength and toughness, which paves the way for the development of many hydrogels used in engineering materials.

Additive manufacturing of highly entangled polymer networks.

Incorporation of polymer chain entanglements within a single network can synergistically improve stiffness and toughness, yet attaining such dense entanglements through vat photopolymerization additive manufacturing [e.g., digital light processing (DLP)] remains elusive. We report a facile strategy that combines light and dark polymerization to allow constituent polymer chains to densely entangle as they form within printed structures. This generalizable approach reaches high monomer conversion at room temperature without the need for additional stimuli, such as light or heat after printing, and enables additive manufacturing of highly entangled hydrogels and elastomers that exhibit fourfold- to sevenfold-higher extension energies in comparison to that of traditional DLP. We used this method to print high-resolution and multimaterial structures with features such as spatially programmed adhesion to wet tissues.

Pure Zwitterionic Hydrogel with Mechanical Robustness and Dynamic Tunability Enabled by Synergistic Non‐Covalent Interactions

AbstractZwitterionic hydrogels with exceptional antifouling properties and biocompatibility have gained widespread attention in biomedical applications. However, achieving robust mechanical performance while maintaining high water content within a single‐network zwitterionic hydrogel remains challenging. Traditional covalent crosslinking strategies often lead to brittleness and irreversible damage. Herein, a novel acylsemicarbazide‐containing carboxybetaine methacrylate (ACBMA) monomer is designed and synthesized that enables the construction of a pure zwitterionic poly(ACBMA) (pACBMA) hydrogel without chemical crosslinkers. The pACBMA hydrogel exhibits high water content exceeding 95% and superior mechanical properties, including compressive fracture stress of 3.92 MPa, compressive strain up to 99% without breaking, and toughness of 212 ± 2.4 kJ m−3, outperforming chemically crosslinked poly(carboxybetaine methacrylate) (pCBMA) hydrogel. Additionally, the pACBMA hydrogel exhibits excellent injectability, moldability, and even recyclability through the preparation of microgels. Through the unique molecular design, the pACBMA hydrogel integrates multiple non‐covalent interactions, including hydrogen bonding, electrostatic interactions, polymer chain entanglement, and steric hindrance of the α‐methyl group. These interactions synergistically contribute to the combination of high hydration, mechanical robustness, and dynamic tunability. These results provide a new design strategy for constructing high‐performance zwitterionic hydrogels with promising potential for diverse biomedical applications.

Enabling low molecular weight electrospinning through binary solutions of polymer blends

The formation of nanofibrous membranes via electrospinning is typically restricted to high molecular weight polymers in an appropriate solvent, correlated with the necessary formation of polymer chain entanglements that are needed to achieve successful production of electrospun fibers. The present work extends the electrospinning of low molecular weight polymers by investigating the electrospinning of a binary solution system consisting of two different low molecular weight polymers, using as a model system polycaprolactone (PCL) and gelatin in different ratios. The viscosities of the polymer solutions were characterized as a proxy for polymer chain entanglement and the resulting fibers were morphologically characterized by SEM imaging and further assessed water contact angle and molecular composition to determine the impact and homogeneity of the binary mixtures. We found that unitary solutions of either PCL or gelatin failed to generate proper fibers despite indications of chain entanglement. In contrast, binary solutions of low molecular weight PCL and gelatin generated different fiber quality and size distributions, depending on the ratio used, with direct correlations between fiber properties and the PCL:Gelatin ratio. It was discovered that the ratio of PCL to gelation was most predictive for successful fiber generation, with effective electrospinning occurring only for a define intermediate range of high blend ratios while both low and high blended binary solutions resulted in poor fiber production. Our study confirmed that this behavior was independent from absolute polymer concentration, indicating a unique interaction between these binary species which exists only under specific ratio concentrations and indicates promising new avenues to process low molecular weight polymers solutions.

Potassium Phthalimide Doped with Delta‐Site Structures to Construct Ultra‐Long Cycle Life Aqueous Zn‐Polymer Batteries

AbstractAqueous Zn‐polymer batteries hold great promise for environmentally friendly energy storage systems. However, the poor cycling performance caused by irreversible structural deformation and polymer chain entanglement during the embedding and de‐embedding processes of Zn2+ and H+ ions is one of the key challenges facing their development. Here a new polyaniline cathode doped is developed with potassium phthalimide using a secondary doping approach. This polymeric electrode integrates the conjugated backbone for charge transport with an anionic phthalimide dopant for constructing a triangular‐site structure, as illustrated by the density functional theory calculations. This unique molecular structure is favorable for improving conductivity and structural stability by effectively modulating the localized electron cloud density. The Zn‐polymer battery holds an outstanding capacity retention of 76.1% after 25,000 cycles at a current density of 1 A g−1 with the coulombic efficiency maintained above 99.4%. This secondary doped polymer strategy offers a new host alternative for the ultra‐long cycle life of Zn‐polymer batteries. The molecular design strategy and the insight into the relationship between the structure and performance may provide some guidelines for developing polymer cathodes with high stability.

Effect of shear flow on the transverse thermal conductivity of polymer melts.

The effect of shear flows on the thermal conductivity of polymer melts is investigated using a reversed nonequilibrium molecular-dynamics (RNEMD) method. We extended the original RNEMD method to simultaneously produce spatial gradients of temperature and flow velocity in a single direction. This method enables accurate measurement of the thermal conductivity in the direction transverse to shear flow. The Weissenberg number defined with the shear rate and the relaxation time of the polymer conformation can uniformly differentiate the occurrence of shear rate dependence of the thermal conductivity across different chain lengths. The stress-thermal rule (STR) (i.e., the linear relationship between anisotropic parts of the stress tensor and the thermal conductivity tensor) holds for entangled polymer melts even under shear flows but not for unentangled polymer melts. Furthermore, once entanglements form in polymer chains, the stress-thermal coefficient in the STR remains independent of the polymer chain length. These observations align with the theoretical foundation of the STR, which focuses on energy transmission along the network structure of entangled polymer chains [B. van den Brule, Rheol. Acta 28, 257 (1989)0035-451110.1007/BF01329335]. However, under driven shear flows, the stress-thermal coefficient is notably smaller than that measured in the literature for a quasiquiescent state without external forces. Although the mechanism of the STR in shear flows has yet to be fully elucidated, our study confirmed the validity of the STR in shear flows. This allows us to use the STR as a constitutive equationfor computational thermofluid dynamics of polymer melts, thus having broad engineering applications.

Percolating coordinated ion transport cells in polymer electrolytes to realize room-temperature solid-state lithium metal batteries

Polymer electrolytes, notable for their good mechanical properties, superior processability, and high electrochemical stability, are promising for high-energy-density lithium metal batteries. However, the ionic conduction of polymer electrolytes is seriously constrained by either the entanglement of polymer chains or binding of anions, particularly at ambient temperatures, making their practical application impossible. Herein, we employ a high-salt-concentration strategy with poly(vinylene carbonate) to construct a percolating network by linking coordinated ion transport cells. The cells, consisting of lithium-ion at the core surrounded by coordinated poly(vinylene carbonate), N,N-dimethylformamide, or incompletely bonded bis(trifluoromethanesulfonyl)imide, ensure an efficient coordination and de-coordination process for ion transport. Thus, a high rate of Li+ transport is realized, achieving an ionic conductivity of 0.82 mS cm−1 at 30 °C. Consequently, the formulated solid-state lithium metal batteries with the poly(vinylene carbonate) electrolyte enable superior stability in cycling under a wide temperature range (0–60 °C), high working voltage (4.5 V), and high mass load (>10 mg cm−2). This simple strategy for creating an ion-percolating network by linking coordinated ion transport cells not only offers new insights into understanding the mechanism for ion transport in polymer electrolytes but also paves the way for the application of solid-state lithium metal batteries.

Do Entangled Polymer Chains Reptate?

AbstractNeutron spin echo spectroscopy of entangled polymer melts [M. Zamponi, et al. J. Phys. Chem. B 2008, 112, 16220], and of tracer diffusion of short polymer chains in highly entangled polymer melt [M. Zamponi et al. Phys. Rev. Lett. 2021, 126, 187801.] and [M. Kruteva et al. Macromolecules 2021, 54, 11384] found the center‐of‐mass mean‐square displacements at shorter times are subdiffusive, heterogeneous, non‐Gaussian, and cooperative. These properties contradict the assumption of reptation within the tube in the tube‐reptation (TR) model, but are in accord with the predictions from the many‐chain cooperative dynamics in the theory of Guenza. The inadequacy of the TR model revealed by the microscopic experiments and theory motivates the author to reexamine previously published data of diffusion of entangled polymer chains from experiments and simulations used to test the TR model. The results reported in this study lead to the conclusion that the key predictions of the TR model are at variance with experimental and simulation data. The cause lies in the reptation hypothesis contradicting the cooperative nature of entangled chain diffusion proven by its dynamics being isomorphic to cooperative diffusion in other materials. The Coupling Model has predictions consistent with the cooperative diffusion properties in interacting materials [Prog. Mater. Sci., 2023, 139, 101130.]. Applied to the entangled polymers, the predictions successfully explain the data, especially those contradicting the TR model. Thus, diffusion of entangled polymer chains is a cooperative many‐chain process in having the universal properties of many‐body cooperative diffusion established in many other interacting materials, and the reptation hypothesis is unwarranted.

Dual Semi-Interpenetrating Networks of Water-Soluble Macromolecules and Supramolecular Polymer-like Chains: The Role of Component Interactions

Dual networks formed by entangled polymer chains and wormlike surfactant micelles have attracted increasing interest in their application as thickeners in various fields since they combine the advantages of both polymer- and surfactant-based fluids. In particular, such polymer-surfactant mixtures are of great interest as novel hydraulic fracturing fluids with enhanced properties. In this study, we demonstrated the effect of the chemical composition of an uncharged polymer poly(vinyl alcohol) (PVA) and pH on the rheological properties and structure of its mixtures with a cationic surfactant erucyl bis(hydroxyethyl)methylammonium chloride already exploited in fracturing operations. Using a combination of several complementary techniques (rheometry, cryo-transmission electron microscopy, small-angle neutron scattering, and nuclear magnetic resonance spectroscopy), we showed that a small number of residual acetate groups (2–12.7 mol%) in PVA could significantly reduce the viscosity of the mixed system. This result was attributed to the incorporation of acetate groups in the corona of the micellar aggregates, decreasing the molecular packing parameter and thereby inducing the shortening of worm-like micelles. When these groups are removed by hydrolysis at a pH higher than 7, viscosity increases by five orders of magnitude due to the growth of worm-like micelles in length. The findings of this study create pathways for the development of dual semi-interpenetrating polymer-micellar networks, which are highly desired by the petroleum industry.

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.