Quantifying and Modeling the Crystallinity of Polymers Confined in Nanopores.

We propose a methodology to characterize the crystalline content of interfacial polymer layers in systems confined at the nanoscale level in a 2D geometry. Based on the crystallinity data of a set of polymers, we introduce a simple model to describe the gradient in crystallinity introduced by confining polymer chains in nanopores. Our model underscores the pivotal role that interfaces play in crystallization and unequivocally contradicts the existence of interfacial "dead" layers where crystallization cannot take place. Further, we verified that the organization of crystals near the pore walls resembles the macromolecular architecture of adsorbed layers, hinting at a strong interplay between crystallization and adsorption.

Challenging Isodimorphism Concepts: Formation of Three Crystalline Phases in Poly(hexamethylene-ran-octamethylene carbonate) Copolymers.

In this work, poly(hexamethylene-ran-octamethylene carbonate) copolycarbonates were synthesized by melt polycondensation in a wide range of compositions. The copolymers displayed some of the characteristic isodimorphic thermal behavior, such as crystallization for all the compositions and a pseudoeutectic behavior of the melting temperature (Tm) versus composition. The pseudoeutectic point was located at 33 mol % poly(octamethylene carbonate) (POC) content (i.e., corresponding to the PH67O33C copolymer). Surprisingly, the crystallinities (Xc) for a wide range of copolymer compositions were higher than those of the parent components, a phenomenon that has not been observed before in isodimorphic random copolymers. The structural characterization, performed by wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering experiments, revealed unexpected results depending on composition. On the one hand, the poly(hexamethylene carbonate) (PHC)- and POC-rich copolymers crystallize in PHC- and POC-type crystals, as expected. Moreover, upon cooling and heating, in situ WAXS experiments evidenced that these materials undergo reversible solid-solid transitions [δ-α (PHC) and δ-α-ß (POC)] present in the parent components but at lower temperatures. On the other hand, a novel behavior was found for copolymers with 33-73 mol % POC (including the pseudoeutectic point), which are those with higher crystallinities than the parent components. For these copolymers, a new crystalline phase that is different from that of both homopolymers was observed. The in situ WAXS results for these copolymers confirmed that this novel phase is stable upon cooling and heating and does not show any crystallographic feature of the parent components or their solid-solid transitions. FTIR experiments confirmed this behavior, revealing that the new phase adopts a polyethylene-like chain conformation that differs from the trans-dominant ones exhibited by the parent components. This finding challenges the established concepts of isodimorphism and questions whether a combination of crystallization modes (isodimorphism and isomorphism) is possible in the same family of random copolymers just by changing the composition.

Fast Fabrication of Porous Amphiphilic Polyamides via Nonconventional Evaporation Induced Phase Separation.

In the present work, we report a facile approach for the fast fabrication of porous films and coatings of long-chain polyamides through a nonconventional evaporation induced phase separation. Because of its amphiphilic nature, polyamide 12 can be dissolved in the mixture of a high-polarity solvent and a low-polarity solvent, while it could not be dissolved in either solvent solely. The sequential and fast evaporation of the solvents leads to the formation of porous structures within 1 min. Moreover, we have investigated the dependence of the pore structures on composition of the solutions, and have demonstrated that our approach can be applied to other long-chain polycondensates, too. Our findings can provide insight on the fabrication of porous materials by using amphiphilic polymers.

A Transparent, Healable and Recyclable Alicyclic Poly(ether-b-amide) Multiblock Copolymer with Ultrahigh Toughness.

Self-healing polyamide multiblock copolymer with robust mechanical properties is highly desired. Here, an alicyclic diamine monomer, isophoronediamine (IPDA), with asymmetric structure and substantial steric hindrance was incorporated into the backbone of poly(ether-b-amide) multiblock copolymer. Based on the phase-lock effect, the mechanical properties and segmental mobility of copolymers can be modulated on a large scale via adjusting the molecular weight of hard segments. An extraordinary tensile strength of 32.0 MPa and an excellent elongation at break of 1881 % were simultaneously achieved, which leaded to a record-high toughness of 328.9 MJ m-3 for self-healable polyamide elastomers. The synergism between the dynamic H-bonding networks and the diffusion of polymer chains contributed to a balance between the mechanical performance and self-healing efficiency of copolymers. Due to the adjustable mechanical performance, rapid scratch self-healing ability and superior impact resistance, the resultant copolymers showed great potential in the fields of protective coatings and soft electronics.

Physical Aging of Polystyrene Confined in Anodic Aluminum Oxide Nanopores.

We investigated the glassy dynamics of polystyrene (PS) confined in anodic aluminum oxide (AAO) nanopores by differential scanning calorimetry. Based on the outcome of our experiments, we show that the cooling rate applied to process the 2D confined PS melt has a significant impact on both the glass transition and the structural relaxation in the glassy state. A single glass transition temperature (Tg) is observed in quenched samples, while slow-cooled PS chains show two Tgs corresponding to a core-shell structure. The former phenomenon resembles what is observed in freestanding structures, while the latter is imputed to the adsorption of PS onto AAO walls. A more complex picture was drawn for physical aging. In the case of quenched samples, we observed a non-monotonic trend of the apparent aging rate that in 400 nm pores, reaches a value almost twice as larger than what is measured in bulk and decreases upon further confinement in smaller nanopores. For slow-cooled samples, by adequately varying the aging conditions, we were able to control the equilibration kinetics and either separate the two aging processes or induce an intermediate aging regime. We propose a possible explanation of these findings in terms of distribution in free volume and the presence of different aging mechanisms.

Stretchable Self-Healing Plastic Polyurethane with Super-High Modulus by Local Phase-Lock Strategy.

In this work, a multiblock polyurethane (PU-Im) consisting of polyether and polyurethane segments with imidazole dangling groups is demonstrated, which can further coordinate with Ni2+ . By controlling the ligand content and metal-ligand stoichiometry ratio, PU-Im-Ni complex with vastly different mechanical behavior can be obtained. The elastomer PU-2Im-Ni has extraordinary mechanical strength (61MPa) and excellent toughness (420 MJ m-3 ), but the plastic PU-4Im-Ni exhibits super-high modulus (515 MPa), strength (63 MPa), and good stretchability (≈800%). The metal-ligand interaction between polyurethane segments and Ni2+ is proved by Raman spectra, dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). The polyurethane segments domain formed by microphase separation is dynamically "locked" by Ni2+ coordinated with imidazole, revealing a local phase-lock effect. The phase-locking hard domains reinforce the PU-Im-Ni complex and maintain stimuli-responsive self-healing ability, while the free polyether segments provide stretchability. Primarily, the water environment with plasticization effect serves as an effective and eco-friendly self-healing approach for PU-Im-Ni plastic. With the excellent mechanical performance, thermal/aquatic self-healing ability, and unique damping properties, the PU-Im-Ni complexes show potential applications in self-healing engineering plastic and cushion protection fields.

Verification of thermodynamic theories of strain-induced polymer crystallization.

We studied the crystallization of nearly "homogeneous" polyethylene glycol (PEG) networks prepared by end-crosslinking of tetra-armed PEG. The influence of stretching ratio and strand length on the melting and crystallization temperature was investigated. The relation of melting temperature and elongation ratio verifies the thermodynamic theories of strain-induced polymer crystallization.

Crystallization of a Self-Assembling Nucleator in Poly(l-lactide) Melt.

In the present work, crystallization of a soluble nucleator N, N', N″-tricyclohexyl-1,3,5-benzenetricarboxylamide (TMC-328) in a poly(l-lactic acid) (PLLA) matrix has been studied at different temperatures. Based on the change in solubility with temperature, different levels of supersaturation of TMC-328 in a PLLA matrix can be obtained. This nucleator presents a fibrous structure produced via self-assembling and develops into an interconnected network when the temperature is lowered. The TMC-328 crystal nuclei density is quantified via optical microscopy, using the average distance of the adjacent fibrillar structure, which shows a steady decrease with the decrease in temperature. The crystallization rates of TMC-328 were assessed through rheological measurements of network formation. Both fibrils' density and crystallization kinetics display a power law dependence on supersaturation. For the first time, the solid-melt interfacial energy, the size of the critical nucleus, and the number of molecules making up the critical nucleus of the nucleator TMC-328 in the PLLA matrix have been determined by adopting the classical nucleation theory. The subsequent crystallization of PLLA induced by this nucleator was investigated as a function of the fibrils' spatial density. The crystallization rate of PLLA is enhanced with the increase in the TMC-328 fibrils' density because of the availability of a larger nucleating surface. The self-assembled fibril of TMC-328 can serve as shish to form a hybrid shish-kebab structure after the crystallization of PLLA, regardless of the number of nucleation sites.

Arbitrarily Reconfigurable and Thermadapt Reversible Two-Way Shape Memory Poly(thiourethane) Accomplished by Multiple Dynamic Covalent Bonds.

The fabrication of a single polymer network that exhibits a good reversible two-way shape memory effect (2W-SME), can be formed into arbitrarily complex three-dimensional (3D) shapes, and is recyclable remains a challenge. Herein, we design and fabricate poly(thiourethane) (PTU) networks with an excellent thermadapt reversible 2W-SME, arbitrary reconfigurability, and good recyclability via the synergistic effects of multiple dynamic covalent bonds (i.e., ester, urethane, and thiourethane bonds). The PTU samples with good mechanical performance simultaneously demonstrate a maximum tensile stress of 29.7 ± 1.1 MPa and a high strain of 474.8 ± 7.5%. In addition, the fraction of reversible strain of the PTU with 20 wt % hard segment reaches 22.4% during the reversible 2W-SME, where the fraction of reversible strain is enhanced by self-nucleated crystallization of the PTU. A sample with arbitrarily complex permanent 3D shapes can be realized via the solid-state plasticity, and that sample also exhibits excellent reversible 2W-SME. A smart light-responsive actuator with a double control switch is fabricated using a reversible two-way shape memory PTU/MXene film. In addition, the PTU networks are de-cross-linked by alcohol solvolysis, enabling the recovery of monomers and the realization of recyclability. Therefore, the present study involving the design and fabrication of a PTU network for potential applications in intelligent actuators and multifunctional shape-shifting devices provides a new strategy for the development of thermadapt reversible two-way shape memory polymers.

Confined Crystallization of Polymers within Nanopores.

Crystallization of polymeric materials under nanoscopic confinement is highly relevant for nanotechnology applications. When a polymer is confined within rigid nanoporous anodic aluminum oxide (AAO) templates, the crystallization behavior experiences dramatic changes as the pore size is reduced, including nucleation mechanism, crystal orientation, crystallization kinetics, and polymorphic transition, etc. As an experimental prerequisite, exhaustive cleaning procedures after infiltrations of polymers in AAO pores must be performed to ensure producing an ensemble of isolated polymer-filled nanopores. Layers of residual polymers on the AAO surface percolate nanopores and lead to the so-called "fractionated crystallization", i.e., multiple crystallization peaks during cooling.Because the density of isolated nanopores in a typical AAO template exceeds the density of heterogeneities in bulk polymers, the majority of nanopores will be heterogeneity-free. This means that the nucleation will proceed by surface or homogeneous nucleation. As a consequence, a very large supercooling is necessary for crystallization, and its kinetics is reduced to a first-order process that is dominated by nucleation. Self-nucleation is a powerful method to exponentially increase nucleation density. However, when the diameter of the nanopores is lower than a critical value, confinement prevents the possibility to self-nucleate the material.Because of the anisotropic nature of AAO pores, polymer crystals inside AAO also exhibit anisotropy, which is determined by thermodynamic stability and kinetic selection rules. For low molecular weight poly(ethylene oxide) (PEO) with extended chain crystals, the orientation of polymer crystals changes from the "chain perpendicular to" to the "chain parallel to" the AAO pore axis, when the diameter of AAO decreases to the contour length of the PEO, indicating the effect of thermodynamic stability. When the thermodynamic requirement is satisfied, the orientation is determined by kinetics including crystal growth direction, nucleation, and crystal growth rate. An orientation diagram has been established for the PEO/AAO system, considering the cooling condition and pore size.The interfacial polymer layer has different physical properties as compared to the bulk. In poly(l-lactic acid), the relationship between the segmental mobility of the interfacial layer and crystallization rate is established. For the investigation of polymorphic transition of poly(butane-1), the results indicate that a 12 nm interfacial layer hinders the transition of Form II to Form I. Block and random copolymers have also been infiltrated into AAO nanopores, and their crystallization behavior is analogously affected as pore size is reduced.

Strain-Induced Form Transition and Crystallization Behavior of the Transparent Polyamide.

A transparent polyamide, poly(4,4'-aminocyclohexyl methylene dodecanedicarboxylamide) (PAPACM12), was studied and characterized by in situ wide-angle X-ray diffraction (WAXD) to establish the relationship between its crystallization behavior, crystalline form transition under external fields, and macroscopic properties. During the heating process, cold crystallization occurred and increased, and there was no form transition below the melting point. During the isothermal process, PAPACM12 exhibited the same crystalline structure as that during the heating process. The crystalline structure of PAPACM12 was attributed to α-form crystal, which is the stable form, according to the WAXD diffraction peaks of the conventional AABB-type polyamides. During stretching deformation, the crystal transition from α-form to γ-form and strain-induced crystallization were observed to contribute to the PAPACM12 with higher breaking strength and elongation. This study firstly determine the crystalline structure of transparent polyamides, and then the controlled strain-induced crystallization and transformation are demonstrated to be effective preparation methods for polyamides with high properties.

Isothermal Crystallization Kinetics of Poly(ethylene oxide)/Poly(ethylene glycol)-g-silica Nanocomposites.

In this work, the crystallization kinetics of poly(ethylene oxide) (PEO) matrix included with poly(ethylene glycol) (PEG) grafted silica (PEG-g-SiO2) nanoparticles and bare SiO2 were systematically investigated by differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM) method. PEG-g-SiO2 can significantly increase the crystallinity and crystallization temperature of PEO matrix under the non-isothermal crystallization process. Pronounced effects of PEG-g-SiO2 on the crystalline morphology and crystallization rate of PEO were further characterized by employing spherulitic morphological observation and isothermal crystallization kinetics analysis. In contrast to the bare SiO2, PEG-g-SiO2 can be well dispersed in PEO matrix at low P/N (P: Molecular weight of matrix chains, N: Molecular weight of grafted chains), which is a key factor to enhance the primary nucleation rate. In particular, we found that the addition of PEG-g-SiO2 slows the spherulitic growth fronts compared to the neat PEO. It is speculated that the interfacial structure of the grafted PEG plays a key role in the formation of nuclei sites, thus ultimately determines the crystallization behavior of PEO PNCs and enhances the overall crystallization rate of the PEO nanocomposites.

Microphase separation/crosslinking competition-based ternary microstructure evolution of poly(ether-b-amide).

The temperature dependence of the rheological properties of poly(ether-b-amide) (PEBA) segmented copolymer under oscillatory shear flow has been investigated. The magnitude of the dynamic storage modulus is affected by the physical microphase separation and irreversible crosslinking network, with the latter spontaneously forming between the polyamide segments and becoming the dominant factor in determining the microstructural evolution at temperatures well above the melting point of PEBA. From the rheological results, the initial temperature of the rheological properties dominated by the microphase separation and crosslinking (T cross) structures were determined, respectively. Based on the two obtained temperatures, the microstructure evolution upon the heating can be separated into the ternary microstructure domains: homogenous (temperature below ), microphase separation dominating (between and T cross), and crosslinking dominating domains (above T cross). When the PEBA is heated to above T cross, the content of crosslinking network increases with time and temperature, leading to an irreversible and non-negligible influence on the rheological, crystallization, and mechanical properties. A more pronounced strain-hardening phenomenon during the uniaxial stretching is observed for the sample with a higher content of crosslinking network.

In vivo Targeting of Liver Cancer with Tissue- and Nuclei-Specific Mesoporous Silica Nanoparticle-Based Nanocarriers in mice.

PURPOSE: Cancer tissue-specific and nuclei-targeted drug delivery is ideal for the delivery of chemotherapy. However, it has only been achieved in in vitro studies mainly due to low efficiency in vivo. In this study, we aimed to establish an efficient dual-targeted system that targets liver cancer tissue as well as the nuclei of cancer cells in vivo. METHODS: We first synthesized TAT peptide (TATp)-mesoporous silica nanoparticle (MSN) complex (TATp-MSN) and generated liposomes that carried liver cancer-specific aptamer TLS11a (TLS11a-LB). We then generated the drug TLS11a-LB@TATp-MSN/doxorubicin (DOX) by mixing TLS11a-LB and DOX-loaded TATp-MSN. After physical and chemical characterization of the nanoparticles, DOX release from these formulations was evaluated at pH 5.0 and 7.4. Furthermore, we also evaluated nuclear localization and cytotoxicity of the drug in H22 cells in vitro and investigated the liver cancer targeting and antitumor activities of the nano-drug in vivo using a H22 tumor-bearing mice model. RESULTS: TLS11a-LB@TATp-MSN/DOX and its controls were confirmed as nano-drugs (<100 nm) using transmission electron microscopy (TEM). The DOX release rate of TLS11a-LB@TATp-MSN/DOX was significantly faster at pH 5.0 than at pH 7.4. TLS11a-LB@TATp-MSN/DOX effectively targeted the nuclei of H22 cells and released DOX with a higher efficiency than that of the control groups. In addition, TLS11a-LB@TATp-MSN/DOX exhibited slight cytotoxicity, but not significantly more than controls. In vivo studies showed that TLS11a-LB@TATp-MSN accumulated in subcutaneous H22 tumors in the right axilla of BALB/c mice, reaching peak levels at 48 h after intravenous injection, respectively, and demonstrated that TLS11a-LB@TATp-MSN/DOX group enhanced tumor treatment efficacy while reducing systemic side effects. CONCLUSION: TLS11a-LB@TATp-MSN/DOX can efficiently deliver DOX to the nuclei of liver cancer cells by dual targeting liver cancer tissue and the nuclei of the cancer cells in mice. Thus, it is a promising nano-drug for the treatment of liver cancer.

A Facile Strategy to Fabricate Antistatic Polyamide 1012/Multi-Walled Carbon Nanotube Pipes for Fuel Delivery Applications.

Developing antistatic long chain polyamide (LCPA) resins and fabricating the corresponding fuel pipes are challenges but necessary. Herein, a facile but effective strategy was put forward to fabricate LCPA resins with a superior conductivity, meeting the requirements of electrostatic sub-conductors. The strategy was based on, first, the incorporation of a large amount (15 wt%) of multi-walled carbon nanotubes (MWCNTs) into a polyamide 1012 (PA1012) matrix as a master batch, which formed a dense conductive network. Subsequently, it was diluted with PA1012 granules to produce base resins, and the reprocessed nanocomposites with a critical content of MWCNTs (3 wt%) could generate an effectively interconnected conductive network, with sparse and thinning features. Using the base resins, fuel pipes for automobiles, petrol stations and high pressure applications were successfully fabricated, where the thin conductive network was transformed into a thick one due to external field-induced re-agglomeration of MWCNTs. In this way, the obtained fuel pipes combined excellent conductive and barrier properties, and mechanical properties at high and low temperatures. These comprehensive properties also arose from the uniform dispersion of MWCNTs in an LCPA matrix, even without coupling agents; the attractive interaction between MWCNTs and the polyamide chains contributed to their strong interface adhesion. Thus, this research provides a versatile approach to fabricating antistatic LCPA resins, which will certainly extend their application to vehicle fuel systems.

Effect of the Crystallization Conditions on the Exclusion/Inclusion Balance in Biodegradable Poly(butylene succinate-ran-butylene adipate) Copolymers.

Biomedical applications of polymers require precise control of the solid-state structure, which is of particular interest for biodegradable copolymers. In this work, we evaluated the influence of crystallization conditions on the comonomer exclusion/inclusion balance of biodegradable poly(butylene succinate-ran-butylene adipate) (PBSA) isodimorphic random copolymers. Regardless of the crystallization conditions, the copolymers retain their isodimorphic character, displaying a pseudo-eutectic behavior with crystallization in the entire composition range. This illustrates the thermodynamic nature of the isodimorphic behavior for PBSA random copolymers. However, depending on the composition, the crystallization conditions affect the exclusion/inclusion balance of the comonomers. Fast cooling favors butylene adipate (BA) inclusion inside the poly(butylene succinate) (PBS) crystals, whereas isothermal crystallization strongly limits it. PBA-rich compositions behave differently. Both fast and slow crystallization formed the ß-phase, whereas BS unit inclusion is favored independently of the cooling conditions. During successive self-nucleation and annealing, the BA inclusion is intermediate between non-isothermal and isothermal conditions, while the crystalline structure of the PBA phase changes from the ß-phase to the more stable α-phase. We propose a simple crystallographic model to explain the changes in the unit cell dimension of the copolymers.

How Confinement Affects the Nucleation, Crystallization, and Dielectric Relaxation of Poly(butylene succinate) and Poly(butylene adipate) Infiltrated within Nanoporous Alumina Templates.

This work describes the successful melt infiltration of poly(butylene succinate) (PBS) and poly(butylene adipate) (PBA) within 70 nm diameter anodic aluminum oxide (AAO) templates. The infiltrated samples were characterized by SEM, Raman, and FTIR spectroscopy. The crystallization behaviors and crystalline structures of both polymers, bulk and confined, were analyzed by differential scanning calorimetry (DSC) and grazing incidence wide angle X-ray scattering (GIWAXS). DSC revealed that a change in the nucleation process occurred from heterogeneous nucleation for bulk samples to homogeneous nucleation for infiltrated PBA and to surface-induced nucleation for infiltrated PBS. GIWAXS results indicate that PBS nanofibers crystallize in the α-phase, as well as their bulk samples. However, PBA nanofibers crystallize just in the ß-phase, whereas PBA bulk samples crystallize in a mixture of α- and ß-phases. The crystal orientation within the pores was determined, and differences between PBS and PBA were also found. Finally, broadband dielectric spectroscopy was applied to study the segmental dynamics for bulk and infiltrated samples. The glass temperature was found to significantly decrease in the PBS case upon infiltration, while that of PBA remained unchanged. These differences were correlated with the higher affinity of PBS to the AAO walls than PBA, in accordance with their nucleation behavior (surface-induced versus homogeneous nucleation, respectively).

Cooking-Inspired Versatile Design of an Ultrastrong and Tough Polysaccharide Hydrogel through Programmed Supramolecular Interactions.

Simultaneously achieving strength and toughness in soft materials remains a challenge, especially for physically crosslinked hydrogels with many inactive interaction sites. In this work, inspired by the cooking of thick soup in China, a facile method that includes free water evaporation of the diluted pregel solution followed by crosslinking (WEC) is proposed to fabricate polysaccharide hydrogels. Herein, without the constraints of viscosity and crosslinking, polymer chains can homogenously approach as much as possible, thereby enabling the transformation of inactive supramolecular interaction (H-bonding and ionic coordination) sites into active sites until reaching the maximum level. Through facilely tuning the concentrating degree, programmed supramolecular interactions, serving as energy-dissipating sacrificial bonds, impart the hydrogels with strength and toughness over a very wide range, where a "ductile-to-tough" transition is discovered to occur first. Using WEC in alginate, the concentration can be as high as 25 wt% without sacrificing processing ability, a result that is significantly beyond common value (3-7 wt%), and the extremely stiff and tough hydrogels are obtained, superior to isotropic alginate hydrogels ever reported. This research offers a facile and versatile strategy to fabricate isotropic polysaccharide hydrogels, which become ideal matrix materials for further fabrication of hybrid or anisotropic hydrogels.

Crystallization Kinetics of Poly(ethylene oxide) under Confinement in Nanoporous Alumina Studied by in Situ X-ray Scattering and Simulation.

While a relatively complete understanding of the nucleation and orientation of polymers under confinement in one-dimensional nanochannels has been achieved, crystallization kinetics investigation of confined polymers is still rare. In this work, we investigated the crystallization kinetics of poly(ethylene oxide) confined in anodic alumina oxide templates with different pore sizes using in situ wide-angle X-ray scattering (WAXS). The crystallization kinetics results were fitted with the Avrami equation. The Avrami index was determined by both "isothermal step crystallization" and in situ WAXS. The crystallization process of polymers under one-dimensional nanopore confinement was simulated by a "one-dimensional lattice model". Based on this model, it is shown that homogeneous nucleation with the simultaneous growth of multiple crystal planes with drastically different growth rates could result in Avrami indexes lower than 1.

Substituting copolymeric poly(alkylenetetrasulfide) for elemental sulfur to diminish the shuttling effect of modified intermediate polysulfides for high-performance lithium-sulfur batteries.

Poly(alkylenetetrasulfide) can be synthesized to replace sulfur in a chitosan-derived porous carbon (CPC) based composite cathode of lithium-sulfur batteries. Introducing a -CH2- or -CH2CH2- unit in-between the S-S bond of a polysulfide (e.g., Li2S4 → Li-S2-CH2-S-Li or Li-S-CH2CH2-S-Li) diminishes the adverse shuttling effect, proved by experimental tests and first-principle calculations.