At present, the coronavirus disease 2019 (COVID-19) pandemic is a global health crisis. Scientists all over the globe are urgently looking forward to an effective solution to prevent the spread of the epidemic and avoid more casualties at an early date. In this study, we establish an effective platform for the prevention of SARS-CoV-2 by combining the neutralization strategy and RNAi technology. To protect normal cells from infection, the customized cells are constructed to stably express viral antigenic receptor ACE2 on the cell membrane. These modified cells are used as bait for inducing the viral entry. The transcription and replication activities of viral genome are intercepted subsequently by the intracellular shRNAs, which are complementary to the viral gene fragments. A pseudotyped virus reconstructed from the HIV lentivirus is utilized as a virus model, by which we validate the feasibility and effectiveness of our strategy in vitro. Our work establishes an initial model and lays the foundation for future prevention and treatment of various RNA viruses.

Flexible hydrogels have shown promise as strain sensors in medical monitoring, human motion detection and intelligent robotics. For a hydrogel strain sensor, certain challenges need to be urgently addressed for practical applications, such as the damage caused by external effects, leading to equipment failure, and the inability to perceive ambient temperature, resulting in single functionality. Herein, a stretchable, self-healing and dual temperature-strain sensitive hydrogel, with a physically-crosslinked network, is designed by constructing multiple dynamic reversible bonds. Graphene oxide (GO) and iron ions (Fe³⁺) act as dynamic bridges in the cross-linked network and are mediated by the covalent and hydrogen bonding, rendering excellent stretchability to the hydrogel. The reversible features of coordination interactions and hydrogen interactions endow excellent recoverability and self-healing properties. Moreover, the incorporated N-isopropyl acrylamide (NIPAM) provides excellent temperature responsiveness to the hydrogel, facilitating the detection of external temperature changes. Meanwhile, the hydrogels exhibited strain-sensitivity, with a wide working range of 1%−300%, fast response and electrical stability, which can be used as flexible sensors to monitor body motions, e.g., speaking and the bending of finger, wrist, elbow and knee. Overall, the hydrogel possesses dual sensory capabilities, combining external temperature and strain, for potential applications in wearable multifunctional sensing devices.

Antimicrobial peptides (AMPs) have been considered as an alternative to small molecule antibiotics since they are difficult to develop antimicrobial resistance. Hyperbranched polylysine (HPL), an AMP mimics, has gained attention due to its broad-spectrum antibacterial activities, but it also suffers from high toxicity. Here we report a facile strategy to engineer the toxicity of HPL by copolymerizing lysine (K) with a hydrophobic amino acid, e.g., alanine (A), tryptophan (W) or phenylalanine (F), to afford hyperbranched random copolymers. These copolymers have comparable antibacterial activities to HPL while their cytotoxicities and in vivo toxicities are lowered when the type and content of hydrophobic amino acid and the size of copolymers are optimized. The G. mellonella infection model demonstrates that the copolymers are effective against theS. aureus infection in vivo. The copolymers kill the bacteria through the disruption of cell membranes and the bacteria do not develop resistance to the copolymers.

Late transition metals have long served as workhorses for vinyl polymerization of norbornene derivatives. Nevertheless, for such catalytic systems, insoluble polynorbornene (PNB) products are often produced which hampers their further detailed characterizations, such as molecular weights, polydispersities, stereoregularities, etc. In this work, we surprisingly found that for a traditional Ni(acac)₂/MAO system that was previously reported to give insoluble PNBs, incorporation of highly bulk salicylaldiminate ligands could significantly improve the solubility of the PNBs in common organic solvents, which allowed for subsequent thorough detailed analysis of the polymer products. Moreover, it was also observed that high-temperature polymerization was beneficial for further improving the PNB’s solubilities due to the decreased molecular weights and stereoregularities. Different ligand skeletons and ligand equivalents were also investigated to give a comprehensive view of their influences on the polymers’ solubilities, and based on these results, a plausible mechanism that caused such a big difference was tentatively proposed.

Porous coatings with the features of muti-interfaces and high specific surface area have emerged as an excellent material platform for the manipulation of porous structures. Layer-by-layer (LbL) assembly technique has been widely used in preparing porous polyelectrolyte coatings. However, the efficient construction of stable film from the LbL technique is still a question. Herein, we reported a new solution to construct a stabilized polyelectrolyte coating with porous structures. Inspired by the mechanical reinforcement of double-network hydrogel, we constructed the poly(ethylenimine) (PEI)/poly(acrylic acid) (PAA) coating by in situ photopolymerization of acrylic acid in the PEI network instead of assembling PEI and PAA. Compared with the LbL films, the in situ polymerized coating kept higher stability after 30 iterations of friction. Porous structures could also be constructed after acid treatment, which was utilized to load lubricant to enhance the lubricating property of the coating. This work provides a new method for the construction of dynamic and stable polyelectrolyte coatings, expediting more development of practical applications.

The toughened poly(L-lactic acid)/poly(butylene succinate-butylene terephthalate) (PLLA/PBST) blend with enhanced melt strength and excellent low temperature toughness and strength was prepared by melt compounding through in situ compatibilization reaction in presence of multifunctional epoxy compound (ADR). The PLLA/PBST blend was an immiscible system, and the compatibility of the PLLA/PBST blend was improved after adding ADR. FTIR and GPC curves confirmed the formation of the PLLA-g-PBST copolymer, which improved the interfacial bonding of the blend and therefore the PLLA/PBST/ADR blend showed excellent melt strength and mechanical properties. For the PLLA/PBST/ADR blend with 70/30 PLLA/PBST content, the complex viscosity increased significantly with increasing ADR content. Moreover, the tensile strength, elongation at break and impact strength all increased obviously with increasing the ADR content. The elongation at break of the blend reached the maximum value of 392.7%, which was 93.2 times that of neat PLLA. And the impact strength of the blend reached the maximum value of 74.7 kJ/m², which was 21.3 times that of neat PLLA. Interestingly, the PLLA/PBST/ADR blend exhibited excellent low-temperature toughness and strength. At –20 °C, the elongation at break of the PLLA/PBST/ADR blend was as high as 93.2%, and the impact strength reached 18.8 kJ/m ². Meanwhile, the tensile strength of the blend at low temperature was also high (64.7 MPa), which was beneficial to the application of PLA in the low temperature field. In addition, the PLLA/PBST/ADR blend maintaind good biodegradability, which was of great significance to the wide application of PLLA.

Here we report a novel polymeric nanogel with stable loading cargo and near-infrared (NIR) controlled release properties. The nanogels are crosslinked by quaternization reactions of biocompatible poly(β-amino esters) and diselenide-bonded crosslinker (DSeDCl) in microemulsions. The hydrophobic cavities of the nanogels have the property of stably encapsulating the hydrophobic guest molecules, resulted from the crosslinked network structure. Due to the redox responsiveness of the diselenide bonds on the DSeDCl crosslinker, the nanogels can respond to oxidant H₂O₂ causing the disintegration of the crosslinked network structure, thus the encapsulated guest cargo molecules will be released. It is noted that, upon loading the photosensitizer IR780, the nanogels can generate reactive oxygen species (ROS) under NIR irradiation to release the cargo. The advantages of encapsulated cargo stability enhanced by chemical cross-linking and remote stimulation response performance via NIR offer great potential of nanogels for applications of cargo controlled release.

The crystallization behavior of polyamide 6,6 (PA66) under complex flow field is of great importance for its final mechanical properties. Poly(vinyl pyrrolidone) (PVP) was applied as crystallization modifying agency to improve processability of PA66. The regulation nature on hydrogen bonds (H-bonds) interaction of PVP was studied upon cooling process. As revealed by in situ FTIR, the sample with 5 wt% PVP displays decreased enthalpy change (ΔH) for both the generation of H-bonds and the transition of H-bonds from “disordered” to “ordered” state, which illustrates the molecular mechanism for the regulation of crystallzation behavior. Moveover, 2D-WAXD is applied to reveal the evolution of microstructure for sample under external injection field. Hermans orientation factor (f_H) decreases obviously with the addition of PVP, because the relaxation of chain segments is promoted as well the crystallization is retarded. The above crystallization and microstructure changes during the processing provokes the improvement of processability without the apparent sacrifice of mechanical properties.

Artificial soft actuators, featured with non-equilibrium internal circumstance and fast, programmable shape transformations, have attracted strong research interest recently due to their flexibility, highly controllable, and designability. However, wireless soft actuators, achieving the locomotion on different large slopes with multiple energy conversion, have been rarely reported. Herein, we create a asymmetric bilayer strategy to construct autonomous soft crawler via “breathing” moisture to motivate the mechanical deformation. The soft crawlers present conspicuous performances including periodic tumbler locomotion predicted via improved Timoshenko’s equation, multiple reversible shape-morphing (circle, helix, despiralization, etc.) determined by their fiber orientation, controlled drive mode (front drive and rear drive) and rapid climb speed (4.76 cm/min) at wide slope angles. Through architecture design, they can be series-wound or shunt-wound to construct multi-joint complex actuators. Besides climbing, a intelligent soft ring-pull with admirable cycle performance for preventing overheating or something untouchable, has been proposed. The soft crawlers also realize multiple energy conversion to be actuated by light irradiation. We envision that this soft crawler system has an enormous potential in intelligent machine, microscopic diagnosis and treatment, biosensing, energy harvesting and conversion.

In the present work, a series of poly(ethylene glycol) grafted polybutene-1 copolymers (PB-g-PEG) were designed and successfully synthesized with reaction intermediate method, of which the branch densities and length could be tuned independently. The branch density varied from 0.39 mol% to 1.23 mol% and the branch length was tuned by employing PEG number-averaged molecular weight (M_n) from 350 Da to 750 Da and 1000 Da. The non-isothermal crystallization and phase transition behaviors of these butene-1 copolymers with varying branches were systematically explored by differential scanning calorimeter. The results first showed that compared with the linear polybutene-1 homopolymer, presence of steric 4-[4-(trimethylsilylalkynyl)-phenyl]-1-butene (TMS) groups suppressed crystallization and phase transition of copolymers. Interestingly, the introduction of long poly(ethylene glycol) (PEG) branches with M_n=350−1000 Da not only elevated the peak temperature of the non-isothermal crystallization but also enhanced the II-I phase transition, with respect to copolymers with TMS groups. Furthermore, the quantitative correlations between phase transition kinetics with the branch parameters (density and length) were explored. It was found that the phase transition presents a non-monotonic trend with increasing branch density and branch length. In this case, the optimal branch density and length obtained were 0.77 mol% and 750 Da, respectively. Employing the small angle X-ray scattering and transmission electron microscopy, a direct correlation between the phase transition kinetics and the long periodicity of separated phase was obtained, which may be due to the increased internal stress and facilitated stress transport.

Bridging the gap between the computation of mechanical properties and the chemical structure of elastomers is a long-standing challenge. To fill the gap, we create a raw dataset and build predictive models for Young’s modulus, tensile strength, and elongation at break of polyurethane elastomers (PUEs). We then construct a benchmark dataset with 50.4% samples remained from the raw dataset which suffers from the intrinsic diversity problem, through a newly proposed recursive data elimination protocol. The coefficients of determination (R²s) from predictions are improved from 0.73−0.78 to 0.85−0.91 based on the raw and the benchmark datasets. The fitting of stress-strain curves using the machine learning model shows a slightly better performance than that for one of the well-performed constitutive models (e.g., the Khiêm-Itskov model). It confirmed that the black-box machine learning models are feasible to bridge the gap between the mechanical properties of PUEs and multiple factors for their chemical structures, composition, processing, and measurement settings. While accurate prediction for these curves is still a challenge. We release the raw dataset and the most representative benchmark dataset so far to call for more attention to tackle the long-standing gap problem.

Stereocomplex crystallization in cyclic polymer blend and cyclic block copolymers was investigated by means of dynamic Monte Carlo simulations. Five polymer systems (linear polymer blend, linear diblock copolymer, cyclic polymer blend, cyclic diblock copolymer and tetrablock copolymer) were established. It was interestingly found that the cyclic polymer blend exhibited the weakest stereocomplexation ability, while the two cyclic block copolymers showed stronger stereocomplexation ability than the linear diblock copolymer. This abnormal improved stereocomplexation ability of the cyclic block copolymers can be attributed to the synergy between the ring chain topology and the block copolymer structure. Compared with the linear block copolymers, the ring chain topology confined segmental motions of cyclic polymer chains to smaller regions, and then the segments belonging to the different blocks in the cyclic block copolymers have more chance to contact with each other. In this way, the cyclic block copolymers had better miscibility between segments belonging to different types of blocks, leading to the stronger stereocomplexation ability.

The study presents the experimental results of measurements of the relaxation time of cryogels formed from various colloid-dispersed systems based on a poly(vinyl alcohol) aqueous solution. It is shown that the value of relaxation time, which characterizes the relationship between the viscosity and elasticity of real bodies, describes the rheological properties of materials more objectively than the traditional assessment of their physical and mechanical characteristics only by the elasticity modulus of the samples.

Langevin dynamics simulations are employed to explore the effects of chain stiffness and electrostatic interaction (EI) on the conformational behavior of a circular semiflexible polyelectrolyte (CSPE) in presence of trivalent counterions. We investigate the effect of bending energy b and the dimensionless Bjerrum length A on the conformational behavior of the CSPE with a fixed chain length. The competition among the EIs, chain stiffness and entropy of the system leads to rich conformations for the CSPE. As the b is less than or equal to 50, The shape of the CSPE changes from a oblate ring to a rod at small A, then to a toroid at intermediateA, and finally to a globule at very large A. However, the globular conformation is not observed for large b. In addition, we find that the number of torus ring increases with A increase, while decreases with b increase. This study should be helpful in gaining insight into the conformational behaviour of charged biopolymer.

Despite extensive researches on the motion of polymer chains on lipid membranes, the effect of membrane fluctuations on polymer chain dynamics remains poorly understood. Here we report single molecule tracking experiments that allow for comparable measurements of polymer chain diffusion dynamics on nanotubular and planar phospholipid membranes. We observe a super-diffusion behavior and no apparent chain-length-dependent mobility of polymer chains on nanotubular membranes, while a Brownian motion and apparent chain-length-dependent mobility of polymer chains on planar membranes. We suggest the super-diffusion nature of polymer chains may be due to the thermal-fluctuations of lipid nanotubes, which can be described from a statistical thermodynamic phenomenon coupling of polymer chain dynamics and surface thermal fluctuations. We suggest that the existence of surface environment fluctuations should influence the dynamics of the adsorbed polymer chains. This study provides previously uncharacterized insights into polymer diffusion dynamics on thermal-fluctuating flexible surfaces, which is essential to understanding the effect of environment fluctuations on polymer chain behaviors.

The mechanical response of polyethylene nano-fibers with the same chain length but different chain numbers are studied by using steered molecular dynamics simulations. The shrinking or stretching forces acted on the chain ends are investigated according to the chain-end distance and temperature under isothermal or continuous warming-cooling conditions, respectively. An inflection point is found in the Force-Distance response when temperature is below 500 K. This inflection point is related to the balance between entropy force and inter-monomer interaction and it reflects the strong effect of crystallization on the mechanical response of the nano-fibers. The force at inflection point is also affected by the buckling effect due to increased stiffness when crystallization occurs. The two stages found in the Force-Temperature response and the difference between the shrinking and stretching forces indicate the hysteresis of crystallization and melting. The forces at different shrinking and stretching rates reveal the entropy contribution upon the mechanical response, indicated by the Ramachandran plot of dihedrals. The chain-conformation entropy is majorly contributed by dihedrals and is quantified by the information entropy of dihedrals, which has a highly similarity to the mechanical Force-Temperature response. The enlarged forces in multiple chains over a single chain are attributed to the enhanced dihedral-conformation entropy. Our study provides a new insight to the dynamically mechanical response of polymer nano-fibers according to the effect of crystallization and entropy contribution.