Thermal and mechanical activation of dynamically stable ionic interaction toward self-healing strengthening elastomers.

Biological tissues can grow stronger after damage and self-healing. However, artificial self-healing materials usually show decreased mechanical properties after repairing. Here, we develop a self-healing strengthening elastomer (SSE) by engineering kinetic stability in an ionomer. Such kinetic stability is enabled by designing large steric hindrance on the cationic groups, which prevents the structural change driven by thermodynamic instability under room temperature. However, once heat or external force is applied to disrupt the kinetic stability, the inherent thermodynamic instability induces the SSEs to form bigger and denser aggregates, thereby the material becomes stronger during the healing process. Consequently, the self-healing efficiency of fractured SSEs is as high as 143%. Unlike conventional ionomers whose mechanical properties change with time uncontrollably due to the thermodynamic instability, the SSEs show tunable self-healing strengthening behavior, thanks to the kinetic stability. This work provides a novel and universal strategy to fabricate biomimetic self-healing strengthening materials.

Influence of Oligopeptide Length and Distribution on Polyisoprene Properties.

The tuning of binding modes of polar groups is the key step to mimicking the structure and properties of natural rubber through the molecular design of synthetic polyisoprenes. Herein, the ordering and binding distances of oligopeptides could be altered systematically by changing their lengths and distribution along the polyisoprene chain, which impose huge impacts on the mechanical properties and chain dynamics of green rubber. In detail, a series of peptide-functionalized polyisoprenes with terminal blocks (B-2A-PIP, B-3A-PIP) or random sequences (R-2A-PIP, R-3A-PIP) are fabricated by using dipeptides (2A) or tripeptides (3A) as crosslinkers to explore the mechanism of terminal interaction on mechanism properties and chain dynamics. B-4A-PIP and R-4A-PIP served as control samples. It is found that the increased oligopeptide length and the block distribution improves the mechanical properties and confine the chain movement by elevate the contents of ordered and compact microstructures, which is indicated by XRD, broadband dielectric spectroscopy (BDS) and consistent with the result of molecular dynamics simulation. New relaxation signals belonging to oligopeptide aggregates are found which showed elevated dielectric strengths upon temperatures increase. Additionally, it also reveals that the binding modes of oligopeptide do not significantly influence the entanglements of polyisoprene.

Tough Underwater Super-tape Composed of Semi-interpenetrating Polymer Networks with a Water-Repelling Liquid Surface.

Despite recent advances in bioinspired underwater adhesives, achieving tough, fast, and stable adhesion in aqueous environments is still challenging. Here, an underwater super-tape with semi-interpenetrating polymer networks (SIPNs) and a water-repelling liquid surface is synthesized. In the SIPN, the linear chains easily diffuse to adapt to the adherends, and the cross-linked chains provide the super-tape with high dimensional stability. Meanwhile, both the linear and cross-linked chains bear many catechol groups, which can not only vigorously interact with the adherends but also form numerous hydrogen bonds serving as sacrificial bonds in the SIPN. Thus, the super-tape shows both high interfacial adhesion and cohesive energy. Moreover, the super-tape is covered with a water-repelling liquid surface by spraying it with traces of a hydrophobic solvent. It is demonstrated that the hydrophobic solvent absorbed on the surface of the super-tape can remove water between the tape and adherends, enabling their intimate contact to form a strong interaction. As such, the super-tape shows excellent instant adhesion property under water, and the adhesive strength and toughness increase with time and reach their maximum values at around 5 h. The maximum debonding energy of the super-tape reaches 3933 J m-2, which is much higher than those of existing double-sided tapes.

Electron-Donating Effect Enabled Simultaneous Improvement on the Mechanical and Self-Healing Properties of Bromobutyl Rubber Ionomers.

Due to the dynamic nature of networks and high mobility of molecular chains, self-healing elastomers are usually confronted with the trade-off between self-healing efficiency and mechanical properties. Herein, a self-healing ionomer with both high mechanical performance and high self-healing efficiency has been successfully developed by grafting bromobutyl rubber (BIIR) with pyridine-based derivatives. Interestingly, the substituents on the pyridine ring can be used to regulate the interaction forces of ionic clusters and molecular dynamics. The electron-donating effect of the substituents facilitates stable π-π stacking between pyridyl ions, inducing the formation of regular and large ion aggregates, thereby improving the mechanical strength of the ionomer. Meanwhile, the plasticizing effect of the substituents reduces the activation energy and relaxation temperature of the ionic aggregates, thus endowing the ionomer with a high self-healing efficiency. As a result, the ionomer shows tensile strength as high as 8.1 ± 0.3 MPa under room temperature and self-healing efficiency of 100 ± 3% at 60 °C. Therefore, this strategy can be easily extended to other halogen-containing polymers, leading to a novel class of self-healing ionomers that hold great promise in diverse applications.

A Degradable and Self-Healable Vitrimer Based on Non-isocyanate Polyurethane.

Developing degradable and self-healable elastomers composed of reusable resources is of great value but is rarely reported because of the undegradable molecular chains. Herein, we report a class of degradable and self-healable vitrimers based on non-isocyanate polyurethane elastomer. Such vitrimers are fabricated by copolymerizing bis(6-membered cyclic carbonate) and amino-terminated liquid nitrile rubber. The networks topologies can rearrange by transcarbonation exchange reactions between hydroxyl and carbonate groups at elevated temperatures; as such, vitrimers after reprocessing can recover 82.9-95.6% of initial tensile strength and 59-131% of initial storage modulus. Interestingly, the networks can be hydrolyzed and decarbonated in the strong acid solution to recover 75% of the pure di(trimethylolpropane) monomer. Additionally, the elastomer exhibits excellent self-healing efficiency (~88%) and fracture strain (~1,200%) by tuning the monomer feeding ratio. Therefore, this work provides a novel strategy to fabricate the sustainable elastomers with minimum environmental impact.

Room-temperature autonomous self-healing glassy polymers with hyperbranched structure.

Glassy polymers are extremely difficult to self-heal below their glass transition temperature (T g) due to the frozen molecules. Here, we fabricate a series of randomly hyperbranched polymers (RHP) with high density of multiple hydrogen bonds, which show T g up to 49 °C and storage modulus up to 2.7 GPa. We reveal that the hyperbranched structure not only allows the external branch units and terminals of the molecules to have a high degree of mobility in the glassy state, but also leads to the coexistence of "free" and associated complementary moieties of hydrogen bonds. The free complementary moieties can exchange with the associated hydrogen bonds, enabling network reconfiguration in the glassy polymer. As a result, the RHP shows amazing instantaneous self-healing with recovered tensile strength up to 5.5 MPa within 1 min, and the self-healing efficiency increases with contacting time at room temperature without the intervention of external stimuli.

Three-Dimensional Programmable, Reconfigurable, and Recyclable Biomass Soft Actuators Enabled by Designing an Inverse Opal-Mimetic Structure with Exchangeable Interfacial Crosslinks.

Despite the unceasing flourishing of intelligent actuators, it still remains a huge challenge to design mechanically robust soft actuators with the characteristics of three-dimensional (3D) programmability, reconfigurability, and recyclability. Here, we utilize fully bioderived natural polymers to fabricate biomass soft actuators (BioSA) integrating all above features through an ingenious microstructure design. BioSA consists of an interconnected inverse opal-mimetic skeleton of sodium alginate (NaAlg) and a continuous matrix of epoxidized natural rubber (ENR), with exchangeable ß-hydroxyl ester linkages at their interfaces. The hydrophilic nature and interconnected structure of the NaAlg skeleton endow BioSA with exceedingly acute humidity response and robust mechanical properties. Meanwhile, the dynamic nature of ß-hydroxyl ester linkages enables the design of complex 3D structured soft actuators with reconfigurability and recyclability. Since both ENR and NaAlg are derived from natural resources, and the water-based manufacturing process is extremely facile and environmentally friendly, this work provides a novel strategy to fabricate 3D programmable intelligent actuators with both robust mechanical properties and sustainability.

MYORG Mutation Heterozygosity Is Associated With Brain Calcification.

BACKGROUND: Biallelic mutations in the MYORG gene were first identified as the cause of recessively inherited primary familial brain calcification. Interestingly, some heterozygous carriers also exhibited brain calcifications. OBJECTIVES: To further investigate the role of single heterozygous MYORG mutations in the development of brain calcifications. METHODS: A nation-wide cohort of Chinese primary familial brain calcification probands was enrolled from March 2016 through September 2019. Mutational analysis of MYORG was performed in 435 primary familial brain calcification probands who were negative for mutations in the other four known primary familial brain calcification-causative genes (SLC20A2, PDGFRB, PDGFB, and XPR1). RESULTS: Biallelic MYORG mutations were identified in 14 primary familial brain calcification patients from 10 unrelated families. Interestingly, 12 heterozygous carriers from seven of these families also exhibited mild-to-moderate brain calcifications. Moreover, single heterozygous mutations were detected in an additional 9 probands and in 7 of their family members affected with brain calcifications. In our cohort, clinical and imaging penetrance of individuals with biallelic mutations were 100%, whereas among individuals with heterozygous mutations, penetrance of imaging phenotype was reduced to 73.7% (28 of 38) and clinical penetrance was much lower. Most (34 of 38) remained asymptomatic whereas 4 carriers had symptoms of uncertain clinical significance (nonspecific depression, epilepsy and late-onset parkinsonism). Compared with individuals with biallelic MYORG mutations, individuals with heterozygous mutations had brain calcifications with much lower calcification scores (P < 2e-16). CONCLUSIONS: Presence of brain calcifications in individuals with heterozygous MYORG mutations suggested a semidominant inheritance pattern with incomplete penetrance. This finding further expanded the genotype-phenotype correlations of MYORG-related primary familial brain calcification. © 2020 International Parkinson and Movement Disorder Society.

Vortioxetine treatment for generalised anxiety disorder: a meta-analysis of anxiety, quality of life and safety outcomes.

OBJECTIVES: The aim of this study was to investigate the efficacy, tolerability, safety, and impact on quality of life (QoL) and functional status of vortioxetine treatment for patients with generalised anxiety disorder (GAD) by performing a meta-analysis of randomised controlled trials (RCTs). DESIGN: Systematic review and meta-analysis. DATA SOURCES: Data mining was conducted in January 2019 across PubMed, EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials Cochrane Library, Web of science and ClinicalTrials.gov. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: All published RCTs, which assessed the effect of vortioxetine treatment for patients with GAD when compared with a placebo group, were included. DATA EXTRACTION AND SYNTHESIS: Relevant data were extracted and synthesised narratively. Results were expressed as standardised mean differences or ORs with 95% CIs. RESULTS: Our meta-analysis showed that multiple doses (2.5, 5 and 10 mg/day) of vortioxetine did not significantly improve the response rates, compared with placebo (OR 1.16, 95% CI 0.84 to 1.60, p=0.38; OR 1.41, 95% CI 0.82 to 2.41, p=0.21; and OR 1.05, 95% CI 0.76 to 1.46, p=0.75). Moreover, there was no statistically significant difference regarding the remission rates, discontinuation for any reason rates, discontinuation due to adverse events rates, Short-Form 36 Health Survey scores or Sheehan Disability Scale scores between administration of multiple doses (2.5, 5 and 10 mg/day) of vortioxetine and placebo. CONCLUSIONS: Although our results suggest that vortioxetine did not improve the GAD symptoms, QoL and functional status impairment of patients with GAD, it was safe and well tolerated. Clinicians should interpret and translate our data with caution, as the meta-analysis was based on a limited number of RCTs.

Ultra-Tough, Strong, and Defect-Tolerant Elastomers with Self-Healing and Intelligent-Responsive Abilities.

Mechanical strength, toughness, and defect tolerance are usually exclusive in most artificial materials. Herein, inspired by many biomaterials that overcome this tradeoff by integrating soft and hard ingredients through elaborate structural designs, we report a facile latex-assembly method to fabricate ultra-tough, strong, and defect-tolerant elastomers. The elastomers are featured by a microscopic inverse opal-mimetic rigid skeleton of dynamically cross-linked chitosan and a continuous soft matrix of vulcanized natural rubber. Such structural design enables the load-bearing capability, sacrificial property, and self-healing ability of the skeleton, the stress redistribution and extensibility of the matrix, and the stiffness variation between hard and soft ingredients, thereby imparting the elastomers with outstanding mechanical strength and defect tolerance, as well as extremely high toughness of 122 KJ m-2, which is even higher than that of the current state-of-the-art titanium alloys. Moreover, the elastomers show prominent humidity sensitivity due to the hydrophilic nature of the chitosan skeleton. Harnessing these advantages, we fabricate a walking robot triggered by humidity variation and shoes that are able to regulate temperature and humidity. The concept of designing a rigid sacrificial skeleton within a soft continuous matrix on the microscale is quite general, enabling the development of high-performance and intelligent materials for emerging applications.

Highly Stretchable and Self-Healing "Solid-Liquid" Elastomer with Strain-Rate Sensing Capability.

To mimic the velocity-sensitive ability of the human skin, we fabricate a class of "solid-liquid" elastomers (SLEs) by interpenetrating polyborosiloxane (PBS) with polydimethylsiloxane (PDMS). PBS forms a dynamic network through boron/oxygen dative bonds, while PDMS is covalently cross-linked to form a permanent network. The permanent network affords a scaffold for the dynamic network, endowing SLEs with high elasticity and structural stability, thereby overcoming the inherent drawbacks such as fluidity and irreversible deformation of conventional solid-liquid materials. Meanwhile, the dissociation and association of the dynamic network is time-dependent. Thus, the modulus of SLEs varies with strain rates, and if the SLEs contain carbon nanotubes, their electric conductivity is also responsive to strain rates. This property can be utilized to fabricate skin-like sensors with the ability to distinguish different contact velocities. Moreover, the dynamic network can dissipate energy and be repaired, leading to the high stretchability and self-healing performance of SLEs.

Towards a Supertough Thermoplastic Polyisoprene Elastomer Based on a Biomimic Strategy.

Natural rubber is one of most famous self-reinforced rubbers thanks to the phenomenon of strain-induced crystallization. It is usually used in a vulcanized form to enhance the mechanical strength but this results in recycling issues. Herein a thermoplastic analogue of vulcanized natural rubber is obtained as a structural mimic. Terminally functionalized polyisoprene rubber B-4A-PIP was prepared by using tetra-analine as physical crosslinking units. The strong binding of tetra-analine groups gave B-4A-PIP a high tensile strength (15 MPa) and breaking strain of 890 %, which is much higher than those of undecorated copolymer B-OH-PIP. B-4A-PIP has a similar onset strain of crystallization and crystallization index to vulcanized natural rubber. Randomly functionalized polyisoprene R-4A-PIP showed a much lower mechanical strength and SIC properties although R-4A-PIP and B-4A-PIP possessed similar molecular weights and amounts of tetra-analine groups.

Self-recovery magnetic hydrogel with high strength and toughness using nanofibrillated cellulose as a dispersing agent and filler.

Fe3O4 nanocomposite hydrogels, with intrinsic magnetism, can be potentially applied in extensive fields. However, the poor mechanical properties and complex fabrication processes of conventional magnetic hydrogels seriously limit their advanced applications. Herein, this work demonstrates an efficient and easily industrialized method to prepare self-recovery magnetic hydrogels with excellent mechanical performances. In this method, Fe3O4 nanoparticles were facilely dispersed in polyacrylamide (PAM) hydrogels with the assistance of nanofibrillated cellulose (NFC), resulting in good magnetism. The tensile strength and elongation at break of hydrogels increase from 150 to 780 KPa, 1400% to 2960%, respectively, due to the unique network structure and the strong hydrogen bonding interaction between NFC and PAM. Moreover, the obtained hydrogels possess the satisfactory self-recovery ability, thermal stability, and shear resistance. We believe this efficient and simple method can expand the application of high-performance composite hydrogels in biological, medical and environmental fields.

Stability, seepage and displacement characteristics of heterogeneous branched-preformed particle gels for enhanced oil recovery.

Inspired by the viscoelastic displacement theory and the advantages of preformed particle gels, we develop an innovative product called branched-preformed particle gel (B-PPG) for enhanced oil recovery. Due to its excellent viscoelastic properties, B-PPG can be used both in profile control and to improve sweep efficiency in heterogeneous reservoirs. Laboratory experiments indicate that B-PPG shows improved stability and long-term aging resistance under high temperature and salinity when compared with HPAM. The migration and displacement behaviors of B-PPG are studied by a series of sandpack core flow experiments. The results show that the B-PPG particles can migrate through the porous media, and the migration is a dynamic process of plugging and flooding. Besides, B-PPG can significantly create fluid diversion and increase the swept volume in low permeability zones. Moreover, micro visualization and oil displacement experiments are also carried out and prove that B-PPG can displace residual oil in small channels, leading to a high swept volume and enhanced displacement efficiency.

Synergistic effect of CB and GO/CNT hybrid fillers on the mechanical properties and fatigue behavior of NR composites.

In this paper, graphene oxide (GO) and carbon nanotube (CNT) hybrid fillers were used to replace partial carbon black (CB), and GO/CNT/CB/NR composites were prepared with excellent crack growth resistance, low heat build-up and superior mechanical properties. Mechanical testing revealed a significant synergistic reinforcement between GO/CNT and CB in NR composites. The improved dispersion of GO/CNT hybrid fillers and CB in the NR matrix was characterized by transmission electron microscopy (TEM). Through the fatigue test, the GO/CNT/CB/NR composites showed excellent fatigue crack growth resistance and low heat build-up compared to CB/NR composites. These properties provide the NR composites with better applications in industry.

Simultaneous reinforcement and toughness improvement of an epoxy-phenolic network with a hyperbranched polysiloxane modifier.

An epoxy-phenolic network is modified with hyperbranched polysiloxane (HBPSi). The addition of HBPSi-2, which has medium molecular weight, can significantly decrease the viscosity of the uncured epoxy-phenolic system and increase the crosslinking density and homogeneity of the cured crosslinking network. With 10% HBPSi-2, the mechanical properties of the samples are improved comprehensively: tensile modulus and maximum strength increase by 11.4% and 36.2%, respectively, while elongation at break and impact strength increase by 153.8% and 186.7%, respectively. The comprehensive improvements in the mechanical properties are attributed to combined effects of crosslinking density, network rigidity, cohesive density and the matrix-modifier compatibility. What is more, HBPSi-2 also significantly increases the char yield of the material and decreases the thermal weight loss rate, indicating an improved thermal stability. All these results may provide a new strategy for toughness and strength improvement of the epoxy-phenolic network.

Super-Resolution Fluorescence Imaging of Spatial Organization of Proteins and Lipids in Natural Rubber.

Natural rubber (NR) with proteins and lipids has superior mechanical properties to its synthetic counterpart, polyisoprene rubber. However, it is a challenge to unravel the morphology of proteins and lipids. Here we used two-color stochastic optical reconstruction microscopy (STORM) to directly visualize the spatial organization of proteins and lipids in NR. We found that the proteins and lipids form an interdispersed stabilizing layer on the surface of NR latex particles. After drying, the proteins and lipids form aggregates of up to 300 nm in diameter. The aggregates physically interact with the terminal groups of polyisoprene chains, leading to the formation of a network, which contributes to the high elasticity and mechanical property of NR. If we remove proteins in NR, the large phospholipid aggregates disintegrate into small ones. However, it does not decompose the network but rather reduces the effective cross-linking density, thus the deproteinized NR is still elastic-like with decreased mechanical property. Removing both proteins and lipids wholly decomposes the network, thus, results in a liquid-like behavior of the rubber. The STORM measurements in this paper enable more insight into the structure-property relationship of NR, which also shows a great potential of STORM in studying the fine structure of polymeric materials and nanocomposites.

Association between chloride-rich versus chloride-restrictive intravenous fluid administration and acute kidney injury in cardiovascular patients in ICU wards.

The aim of the study was to investigate the therapeutic effect of chloride-restrictive fluid to prevent acute kidney injury (AKI) in cardiovascular patients in intensive care unit (ICU) wards. Between January 2013 and September 2014, 456 patients admitted to ICU wards following diagnosis of cardiovascular disease were recruited and randomized to receive chloride-rich (232 patients) or chloride-restrictive (224 patients) fluid. The baseline characteristics and incidence of Kidney Disease Improving Global Outcomes (KDIGO)-defined AKI was then compared. No significant difference was identified in the baseline characteristics between the two groups. The incidence of moderate-to-severe KDIGO-defined AKI was significantly decreased in patients who received chloride-restrictive fluid. In conclusion, chloride-restrictive may be a novel effective intervention in preventing KDIGO-defined AKI in cardiovascular patients in ICU wards.

Observing Nucleation Transition in Stretched Natural Rubber through Self-Seeding.

Potential competition between fringed-micelle nucleation (N1) and folded-chain nucleation (N2) widely exists in strain-induced crystallization (SIC). However, during uniaxial deformation, no in situ observational evidence of nucleation transition from N2 to N1 in SIC of natural rubber (NR) has been reported yet. In this work, self-seeding provides an effective way for this observation. By the introduction of residual TIC (temperature-induced crystallization)-melting crystallites into pure NR system, in situ synchronic WAXD revealed the formation of low-oriented crystal in the initial deformation stage, which gradually evolves into highly oriented crystal at last. The low-oriented crystal is related to secondary folded-chain nucleation (N2) on the surface of residual TIC-melting crystallites (self-seeding), while newly formed highly oriented crystal is associated with N1. For the first time, the concept of "self-seeding" is innovatively applied to SIC process so that NR exhibits clear nucleation transition phenomenon. Further, theoretical computation of nucleation barrier in the special NR system well reflects that self-seeding has the role of both increasing critical strain of nucleation transition and decreasing onset strain of SIC, thus providing conditions for the observation.

Resveratrol inhibits dysfunction of dendritic cells from chronic obstructive pulmonary disease patients through promoting miR-34.

BACKGROUND: Resveratrol has demonstrated many beneficial effects against aging, including anti-inflammatory and antioxidant roles. The present study was designed to observe the effects of resveratrol on the dysfunction of dendritic cells (DCs) from COPD patients and its possible mechanism and use in the treatment for COPD. METHODS: Flow cytometry analysis was used to examine the expression of costimulatory markers CD80 and CD86 and ELISA was used to examine the secretion of IFN-α. Expression of miR-34 was examined by using real-time PCR. Expression vector of miR-34, LV3-miR-34 was also constructed and transfected into DCs to observe the effects on functions of DCs. RESULTS: The results showed that there was remarkable upregulation of CD80 and CD86 and secretion of cytokines IFN-α in DCs from COPD patients. Resveratrol displayed a dose-dependent cytotoxicity action over 10 µg/mL and pretreatment with resveratrol inhibited upregulation of CD80 and CD86 and secretion of cytokines IFN-α. Further study showed resveratrol upregulated the expression of miR-34, which inhibited the dysfunction of DCs. CONCLUSION: These proofs suggest that resveratrol inhibited dysfunction of DCs from COPD patients through promoting miR-34.