Polyrotaxane Research Articles

Synthesis, Characterization, and Potential Application of Cyclodextrin-Based Polyrotaxanes for Reinforced Atelocollagen Threads.

Preparing strong and flexible atelocollagen-based materials for biomedical applications is still a challenging task. To address this challenge, this study describes the synthesis and characterization of water-soluble polyrotaxanes (PRs) with different coverage ratios and molecular weights of axle polymers, and their potential applications for PR-reinforced atelocollagen threads (PRATs). A novel method was established for the syntheses of PRs with relatively low coverage ratio at the sub-gram scale, in which the aldehyde groups were employed as crosslinking sites for preparing the PRATs via reductive amination. The aldehyde groups were successfully quantified by 1H nuclear magnetic resonance spectroscopy using 1,1-dimethylhydrazine as an aldehyde marker. Fourier-transform infrared and thermogravimetric analysis measurements supported the characterization of the PRs. Interestingly, tensile testing demonstrated that coverage ratio affected the mechanical properties of the PRATs more strongly than molecular weight. The insights obtained in this study would facilitate the development of soft materials based on atelocollagens and PRs.

Mechanically Interlocked Vitrimer Based on Polybenzoxazine and Polyrotaxane

A mechanically interlocked vitrimer (MIV) based on a benzoxazine monomer and polyrotaxane (PR) has been prepared through a mechanically interlocked network (MIN) and dynamic covalent bond chemistry. The dynamic transacetalation exchange through the N,O-acetal-type polybenzoxazine (PBz) structure was catalyzed by a tin compound. Compared to the controlled PBz vitrimer without a MIN, the designed PBz MIV shows enhanced mechanical performance including ductility and tensile strength while maintaining relatively high Young’s modulus and glass transition temperature (Tg). The PBz MIV can be reprocessed several times without compromising mechanical performance and thermal stability. The PBz MIV also exhibits a faster dynamic bond exchange and a lower activation energy compared to the controlled PBz vitrimer due to the mobile intramolecular motions of PR in the network allowing for a dynamic bond exchange in the MIV more readily. The usefulness of the present study for the preparation of high-performance eco-friendly thermosetting vitrimers is discussed.

Epoxy resins containing epoxy-modified polyrotaxanes

The toughening of epoxy resins is important for their applications in coatings, adhesives, and composite materials. In our previous study, we introduced polyrotaxane (PR), which comprises poly-ε-caprolactone (PCL)-grafted α-cyclodextrins (α-CDs) and a polyethylene glycol (PEG) axial chain, into epoxy resins as an additive and observed that the presence of PR causes an additional viscoelastic relaxation and enhances the mechanical toughness. In this study, we modified the side chain ends of PR with epoxy groups (PR-E) to enable incorporation into crosslinked epoxy networks. The chemical bonding of PR-E to the epoxy resins suppressed the local dynamics of the PCL graft chains and enhanced the mechanical properties.

Polyrotaxane in-situ copolymerization stretchable supramolecular hydrogels for photo-controlled cascade energy transfer

Amphiphilic polysorbate (Tween 80) encapsulated hydrophobic methyl acrylate (MA), spiropyran (SP), nitrobenzoxadiazole (NBDAE) and cyanine 5 (Cy5) was mixed to form micelles, which in-situ copolymerized with acrylamide (AM) and polyrotaxane (PR) containing polyethylene glycol (PEG) threaded into vinyl modified α-cyclodextrin (α-CD) with amantadine end-capping to form stretchable supramolecular hydrogel. Benefiting from the sliding cross-linking points of PR, the hydrogel exhibited excellent mechanical properties (1300 % breaking strain and 0.26 MPa breaking stress). Meanwhile, photoreactive achievement of reversible SP acted as primary energy acceptor tuned cascade energy transfer from energy donor NBDAE to secondary acceptor Cy5 (energy transfer efficiency = 80 % for primary transfer, 65 % for secondary transfer). Therefore, this stretchable supramolecular hydrogel material can achieve phototunable multi-color emission and be applied in the field of time-resolved information anti-counterfeiting.

Exploring Receptor Binding Affinities and Hepatic Cell Association of N-Acetyl-d-Galactosamine-Modified β-Cyclodextrin-Based Polyrotaxanes for Liver-Targeted Therapies.

Acid-degradable polyrotaxanes (PRXs) containing threading β-cyclodextrins (β-CDs) are promising candidates for therapeutic applications of β-CDs in metabolic diseases with cholesterol overload or imbalance. To improve cellular uptake specificity and efficiency of PRXs in hepatocytes, N-acetyl-d-galactosamine (GalNAc)-modified PRXs were developed to facilitate asialoglycoprotein receptor (ASGR)-mediated endocytosis. Binding affinity studies revealed that the dissociation constant (KD) values between recombinant ASGR and GalNAc-PRXs decreased with an increase in the number of modified GalNAc units. Additionally, the KD values for GalNAc-PRXs were smaller than those for GalNAc-modified β-CD and amylose, suggesting that the PRX backbone structure improves the binding affinity with ASGR. However, the intracellular uptake levels of GalNAc-PRXs in HepG2 cells increased with a decrease in the number of modified GalNAc units, which was opposite to the trend observed in the binding affinity study. We found that GalNAc-PRXs had a large number of GalNAc units localized in recycling endosomes, resulting in the low intracellular uptake. The cholesterol-reducing abilities of GalNAc-PRXs were assessed using cholesterol-overloaded HepG2 cells. GalNAc-PRXs with a small number of GalNAc units were demonstrated to show superior cholesterol-reducing effects compared to previously designed acid-degradable PRX and clinically tested β-CD derivatives. Thus, we conclude that GalNAc modification is a promising molecular design for the therapeutic application of β-CD-threaded PRXs in various metabolic diseases with cholesterol overload or imbalance in the liver.

Silent elongation of polyrotaxane and its composites

Polyrotaxanes (PR) have attracted great interest due to their unique mechanical properties, exhibiting the pulley effect, via their slide-ring topological structure. Flexible and functional composite materials consisting of PR and inorganic particles, particularly those with plasma-surface modifications, have also shown higher toughness, even with large amounts of inorganic particles present. In this study, we verified the effect of neat PR and its composites with graphene nanoplates or carbon nanofibers by measuring acoustic emission (AE). Simultaneous AE and tensile measurements were tested several times for each sample, and AE signals during elongation were acquired. It revealed that the conventional fixed cross-linked elastomer materials showed AE signals in the entire tensile region, while the movable-cross-linked materials of PR showed almost no AE signal counts. This suggests that neat PR had almost no microscopic fracture before final breakage via the pulley effect. PR composites with plasma-surface-modified fillers showed a lower number of AE signals than that with unmodified fillers. This might be due to the surface modification of fillers, which improved filler dispersibility and/or prevented a large drop in the mobility of cross-linking points.

Fracture Behavior of Polybenzoxazine Toughened by Polyrotaxane Molecules and Core–Shell Rubber

The inherent brittleness of polybenzoxazines (PBas) makes them difficult for high-performance microelectronics and composite applications. Conventional toughening approaches are either ineffective or cause a reduction in the glass transition temperature (Tg) of PBa. Polyrotaxane (PR), a mechanically interlocked supramolecular polymer, is an effective toughening agent to improve the tensile strength and fracture toughness of various polymers due to its unique topological structure. In this study, the effect of the molecular weight and functional groups of PRs on the morphology and mechanical properties of PR-modified PBa was investigated. PBa toughened by well-dispersed epoxide-functionalized PR (EPR) and benzoxazine-functionalized core–shell rubber (BCSR) was found to greatly enhance fracture toughness without compromising Young’s modulus or Tg. The fracture toughness is significantly improved from 0.82 MPa m1/2 for neat PBa to 1.49 MPa m1/2 for PBa/EPR/BCSR. The synergistic toughening effect is explained by the molecularly dispersed EPR in the PBa network, which results in higher network chain mobility, which promotes more cavitation of BCSR and triggers larger matrix plastic deformation. It is believed that the knowledge gained from the present study can help develop tougher polymers for vast engineering applications, especially in electronics, automotive, and aerospace applications.

Supermolecule-Drug Conjugates Based on Acid-Degradable Polyrotaxanes for pH-Dependent Intracellular Release of Doxorubicin.

Doxorubicin (DOX)-conjugated acid-degradable polyrotaxanes (PRXs) were designed as supramolecular drug carriers capable of releasing drugs in acidic cellular environments. Acid-degradable PRXs composed of α-cyclodextrin (α-CD) as a cyclic molecule, poly(ethylene glycol) (PEG) as a polymer axis, and N-triphenylmethyl (N-Trt) groups as an acid-labile stopper molecules were synthesized and DOX was conjugated with the threaded α-CDs in the PRXs. Because the acid-induced cleavage of N-Trt groups in PRXs leads to PRX dissociation, the DOX-modified α-CDs were released under acidic conditions (pH 5.0). The cytotoxicity of DOX-conjugated PRXs in colon-26 cells revealed significant cell death for DOX-conjugated PRXs after 48 h of treatment. Confocal laser scanning microscopy (CLSM) analysis revealed that the fluorescence signals derived from DOX-conjugated PRXs were observed in cellular nuclei after 48 h, suggesting that the DOX-modified α-CDs were released and accumulated in cellular nuclei. These results confirmed that acid-degradable PRXs can be utilized as drug carriers capable of releasing drug-modified α-CDs in acidic lysosomes and eliciting cytotoxicity. Overall, acid-degradable PRXs represent a promising supramolecular framework for the delivery and intracellular release of drug-modified α-CDs, and PRX-drug conjugates are expected to contribute to the development of pH-responsive drug carriers for cancer therapy.

Strengthening and toughening of polybenzoxazine by incorporation of polyrotaxane molecules

A mechanically interlocked supramolecule polyrotaxane (PR) was utilized as a functional additive to modify the hydrogen bonding (H-bonding) and cross-linking network of polybenzoxazine (PBa). Epoxide and hydroxyl groups at the terminal end of polycaprolactone grafted on CDs were chosen to investigate how these functional groups influence H-bonding, morphology, and mechanical properties of PBa matrix. Fourier transform infrared spectroscopy and differential scanning calorimetry results show evidence of successful manipulation of H-bonding and curing kinetics of PBa in the presence of the functionalized PR. After curing, epoxide functionalized PR (EPR) shows a strong interaction with PBa, leading to molecular level dispersion in PBa compared to PR with the hydroxyl functional group. By introducing only 4 wt% of EPR in PBa, the ductility and fracture toughness of PBa are greatly improved without a noticeable drop in Young's Modulus, which is attractive for aerospace and microelectronic applications.

Slide‐Ring Supramolecular Mechanoresponsive Elastomer with Reversible Luminescence Behavior

AbstractA solid slide‐ring supramolecular elastomer is constructed by free‐radical polymerization of 2‐(2‐methoxyethoxy)ethyl methacrylate, acrylate‐modified perylene diimides (PDI), and the polyrotaxane (PR) cross‐linker. Benefiting from reciprocating shuttle function of slide‐ring PR formed by acrylate‐modified α‐cyclodextrin threading on polyethylene glycol, the resultant supramolecular elastomer not only presents excellent tensile property, toughness, and fatigue resistance up to 100 cycles, but also gives reversible mechano‐induced fluorescence changes from red to orange luminescence due to a reversible conversion of PDI dimer to monomer upon mechanical stretching. After the dye molecule Nile blue is added as a fluorescent acceptor, the supramolecular elastomer exhibits highly reversible mechano‐induced regulation of energy transfer and can perform five cycles without optical fatigue. This bifunctional mechanochromic slide‐ring supramolecular elastomer, which not only possesses mechanically reversible motion of the slide‐ring cross‐linkers but also has the mechanochromic response of fluorophore, endows the intrinsic superiority of slide‐ring into fatigue resistant mechanoresponsive strain sensing materials.

Understanding the Electrochemical Performances of Si Anodes Incorporating Mechanically Interlocked Binders Prepared from α-Cyclodextrin-Based Polyrotaxanes

Rechargeable Li-ion batteries with larger autonomy are needed to meet increasing market demands, hence the intensive research effort to switch from graphite to silicon (Si) anodes, despite their detrimental massive volume changes upon cycling. Many elegant polymer chemistries have addressed this issue by designing smart binders capable of buffering Si electrodes fracturing and maintaining their overall structure. In this sense, self-healing PR–PAA binders relying on the α-cyclodextrin (α-CD) supramolecular chemistry and prepared by cross-linking poly(acrylic acid) (PAA) with α-CD based polyrotaxanes (PR) have recently been proposed. We herein further explore this binder chemistry to understand the proper function of such mechanically interlocked networks. We successfully synthesized a wide range of PR–PAA binders by varying their structural parameters: the doping ratio of PR, the cross-linking density, as well as the polymer molecular weight and the PR ring coverage. Then, their electrochemical performances were tested in nano-sized Si composite electrodes, and a structure/property correlation was evidenced. By promoting the α-CD sliding motion through both an increase of the PR doping fraction and a decrease of the PR ring coverage, we succeeded in making a PR−PAA-based Si electrode having an initial capacity of >3000 mA h/g and showing 82% capacity retention after 100 cycles as opposed to only 42% for PAA-based Si electrodes. A resulting better stress dissipation was evidenced by ex situ scanning electron microscope analysis as well as operando internal stress monitoring experiments via optical sensors. Altogether, this work emphasizes the benefits that CD-based supramolecular architectures can offer to the battery community for designing self-healing binders.

Bioinspired Oxidation-Resistant Catechol-like Sliding Ring Polyrotaxane Hydrogels

Adaptable hydrogels have been used in the biomedical field to address several pathologies, especially those regarding tissue defects. Here, we describe unprecedented catechol-like functionalized polyrotaxane (PR) polymers able to form hydrogels. PR were functionalized with the incorporation of hydroxypyridinone (HOPO) moieties into the polymer backbone, with a degree of substitution from 4 to 22%, depending on the PR type. The hydrogels form through the functionalized supramolecular systems when in contact with a Fe(III) solution. Despite the hydrogel formation being at physiological pH (7.4), the HOPO derivatives are extremely resistant to oxidation, unlike common catechols; consequently, they prevent the formation of quinones, which can lead to irreversible bounds within the matrix. The resulting hydrogels demonstrated properties lead to unique hydrogels with improved mechanical behavior obtained by metallic coordination crosslinking, due to the synergies of the sliding-ring PR and the non-covalent (reversible) catechol analogues. Following this strategy, we successfully developed innovative, cytocompatible, oxidative-resistant, and reversible crosslinked hydrogels, with the potential of being used as structural self-materials for a variety of applications, including in the biomedical field.

Control of the threading ratio of rings in a polypseudorotaxane: A computer simulation study

As a conceptually new class of polymers, mechanically interlocked polymers (MIPs) have been attracting much attention during last decades due to their uniqueness in property profiles and promising industrial applications. The unique properties of MIPs are essentially rooted in special modes of motion of its basic constituents, e.g., physical properties of polyrotaxanes (PRs) or polyrotaxane (PR) derivatives mainly stem from sliding motion of rings along the linear axle in a PR. Control of the threading ratio of rings in a PR is a key to regulate the sliding behavior of the rings and thus the property profiles of PRs or PR derivatives. Usually, polypseudorotaxane (PPR), a supramolecular complex composed of a linear polymer threaded by a number of rings, acts as a precursor of a PR, which can be formed in experiments by simply end-capping of the PPR. Thus, controlling the threading ratio of a PPR is determinant for regulation of the threading ratio of a PR formed from it. In this work, by using molecular dynamics simulation of the Kremer-Grest model, we systematically investigate dependence of the threading ratio of rings (e.g., mean value of the threading ratios and fluctuation feature of the normalized number of threaded rings) in PPRs obtained on those key relevant factors, including molecular interactions between the linear polymer (its backbone and chain ends) and the rings, chain length and stiffness of the linear polymer, ring concentration, temperature. It is concluded that the threading ratio of rings in PPR over a wide range can be effectively controlled by tuning the above-mentioned molecular parameters. Finally, we propose a theoretical understanding of main simulation results based on the two-state model.

Activated cholesterol metabolism is integral for innate macrophage responses by amplifying Myd88 signaling.

Recent studies have shown that cellular metabolism is tightly linked to the regulation of immune cells. Here, we show that activation of cholesterol metabolism, involving cholesterol uptake, synthesis, and autophagy/lipophagy, is integral to innate immune responses in macrophages. In particular, cholesterol accumulation within endosomes and lysosomes is a hallmark of the cellular cholesterol dynamics elicited by Toll-like receptor 4 activation and is required for amplification of myeloid differentiation primary response 88 (Myd88) signaling. Mechanistically, Myd88 binds cholesterol via its CLR recognition/interaction amino acid consensus domain, which promotes the protein's self-oligomerization. Moreover, a novel supramolecular compound, polyrotaxane (PRX), inhibited Myd88‑dependent inflammatory macrophage activation by decreasing endolysosomal cholesterol via promotion of cholesterol trafficking and efflux. PRX activated liver X receptor, which led to upregulation of ATP binding cassette transporter A1, thereby promoting cholesterol efflux. PRX also inhibited atherogenesis in Ldlr-/- mice. In humans, cholesterol levels in circulating monocytes correlated positively with the severity of atherosclerosis. These findings demonstrate that dynamic changes in cholesterol metabolism are mechanistically linked to Myd88‑dependent inflammatory programs in macrophages and support the notion that cellular cholesterol metabolism is integral to innate activation of macrophages and is a potential therapeutic and diagnostic target for inflammatory diseases.

Reversible Ratiometric Mechanochromic Fluorescence Switching in Highly Stretchable Polyurethane Elastomers with Ultratoughness Enhanced by Polyrotaxane

Multistimuli-responsive polymers containing mechanophoric motifs are highlighted as promising mechano-luminescent materials upon stretching via optical fluorescence signals. Herein, we report a distinct ratiometric force-induced fluorescence changes from green-emissive napthalimide stopper (donor) embedded in polyrotaxane (PR) cross-linkers to red-emissive rhodamine mechanophore (acceptor) incorporated in polyurethane (PU) backbones. The utilization of PR (1 wt %) can significantly enhance both toughness and stretchability in our targeted PU elastomers, where the mechanical work is largely dissipated by the ring-sliding motion and pulley effects of PR cross-linkers during stretching. Therefore, the simple soft robotic behavior with ultrafast shape memory and reversible ratiometric mechanochromic fluorescence switching by heating (60 °C) in PR-based PU films provide a distinctive strategy for the construction of molecular machines in the high-performance elastomers, which also offer pathways for practical applications of stimuli-responsive polymers in highly stretchable artificial muscles featuring both outstanding pulley effects on enhanced mechanical properties and novel signal variations of mechanochromic fluorescence simultaneously.

Dynamic nitric oxide/drug codelivery system based on polyrotaxane architecture for effective treatment of Candida albicans infection

The low permeability of antifungal agents to fungal biofilms, which allows the continued survival of the fungus inside, is a key issue that makes fungal infections difficult to cure. Inspired by the unique dynamic molecule motion properties of the polyrotaxane (PR) nanomedicine, herein, a dynamic delivery system Clo@mPRP/NONOate was fabricated by co-loading nitric oxide (NO) and the antifungal drug clotrimazole (Clo) onto the α-cyclodextrin (α-CD) PR modified mesoporous polydopamine (mPDA) nanoparticles, in which pentaethylenehexamine (PEHA) was grafted to α-CDs. The cationic α-CDs endowed this dynamic NO/Clo codelivery system with the ability to effectively attach to fungal biofilms through electrostatic interaction, while the introduction of PRs with flexible molecule motion (slide and rotation of CDs) enhanced the permeability of nanoparticles to biofilms. Meanwhile, NO could effectively inhibit the formation of fungal hyphae, showing an dissipating effect on mature biofilms, and could be further combined with Clo to completely eradicate fungi inside the biofilms. In addition, the dynamic system Clo@mPRP/NONOate could efficiently and synergistically eliminate planktonic Candida albicans (C. albicans) in a safe and no toxic side effect manner, and effectively cured C. albicans-induced vaginal infection in mice. Therefore, this dynamic NO/Clo codelivery system provided an effective solution to the clinical treatment of C. albicans-induced vaginal infection, and the application prospect could even be extended to other microbial infectious diseases. Statement of significanceA dynamic codelivery system based on cationized cyclodextrin polyrotaxane combining nitric oxide and antifungal drugs clotrimazole was prepared to deal with the issue of clinical fungal biofilm infection. This dynamic codelivery system could be attached to the Candida albicans biofilms and penetrate into biofilm via flexible molecular mobility to effectively eradicate the fungi. This dynamic codelivery system could synergistically and efficiently eliminate planktonic-state Candida albicans, but did not show significant cytotoxicity to normal somatic cells.

Phytic acid as a biomass flame retardant for polyrotaxane based phase change materials

Petrochemical resources are facing depletion and human long-term survival needs sustainable development. In this era, it is very important to develop new sustainable phase change materials (PCMs), because it has shown great application value in the effective utilization of industrial waste heat, solar energy harvesting, and electronic heat treatment. In this work, we reported a biomass phytic acid (PA) modified polyrotaxane (PLR) as PCMs for thermal management. The tensile performances, fire safety, phase transition performances of the PCMs were investigated. It is found that all the tensile properties, char residual, and fire-safety of PLR can be enhanced remarkably by introduce of PA. Typically, the Young's modulus, yielding strength and tensile strength of the PLR were 826.7 MPa, 14.2 MPa and 14.2 MPa, respectively, and significantly increased to 1527.4 MPa, 22.1 MPa, and 24.0 MPa respectively, with the addition of 10 wt% of PA. Elongation (>783 %) for all modified PCMs was gradually increased with the increase of PA contents. Thermal analysis shows that the fire safety of PLR is significantly improved. Specifically, for the best sample PLR-PA30, the pHRR could decrease by 54.2 %, THR decreased by 34.0 %; and the LOI increased from 20.8 % to 28.2 %. The PCMs showed the perfect form stability and leakage-proof performance, enhanced thermal conductivity and outstanding cycle properties. Notably, its biomass source, and high flexibility, enhanced fire safety and completely green pathway may provide a practical way for the highly flexible and sustainable packaging of electronic devices for heat treatment.

Supramolecular Surface Coatings with Acetylated Polyrotaxane-Based Triblock Copolymers for Thermal Regulation of Cell Adhesion and Fabrication of Cell Sheets.

Polyrotaxanes (PRXs) containing acetylated α-cyclodextrins exhibit a temperature-dependent phase transition in aqueous solutions across their lower critical solution temperature (LCST) of approximately 26.6 °C. To gain insights into the interactions of acetylated PRXs (Ac-PRXs) with biological components, thermoresponsive supramolecular surfaces were prepared by coating tissue culture polystyrene (TCPS) surfaces with Ac-PRX triblock copolymers, and their surface properties across the LCST were evaluated. The wettability and protein adsorption of Ac-PRX-coated surfaces changed significantly between 10 and 37 °C, whereas the uncoated TCPS and unmodified PRX-coated surfaces did not alter the wettability and protein adsorption at 10 and 37 °C. The adhesion, proliferation, morphology, and adhesion strength of NIH/3T3 cells on Ac-PRX-coated surfaces were found to be similar to those of the uncoated and unmodified PRX-coated surfaces. However, the adhesion strength of NIH/3T3 cells on Ac-PRX-coated surfaces decreased drastically at 10 °C. Consequently, the cells spontaneously detached from the Ac-PRX-coated surfaces without enzymatic treatment. Additionally, when incubating confluent cells at 10 °C, the cells detached from Ac-PRX-coated surfaces as cell sheets while retaining extracellular matrix proteins. The findings of this study provide new directions for the design of thermoresponsive supramolecular biointerfaces for applications in bioseparation and cell manipulation.

Chemorheological Monitoring of Cross-Linking in Slide-ring Gels Derived From α-cyclodextrin Polyrotaxanes.

Despite hundreds of studies involving slide-ring gels derived from cyclodextrin (CD)-based polyrotaxanes (PRs), their covalent cross-linking kinetics are not well characterized. We employ chemorheology as a tool to measure the gelation kinetics of a model slide-ring organogel derived from α-cyclodextrin/poly (ethylene glycol) PRs cross-linked with hexamethylenediisocyanate (HMDI) in DMSO. The viscoelastic properties of the gels were monitored in situ by small-amplitude oscillatory shear (SAOS) rheology, enabling us to estimate the activation barrier and rate law for cross-linking while mapping experimental parameters to kinetics and mechanical properties. Gelation time, gel point, and final gel elasticity depend on cross-linker concentration, but polyrotaxane concentration only affects gelation time and elasticity (not gel point), while temperature only affects gelation time and gel point (not final elasticity). These measurements facilitate the rational design of slide-ring networks by simple parameter selection (temperature, cross-linker concentration, PR concentration, reaction time).

Slidable Cross-Linking Effect on Liquid Crystal Elastomers: Enhancement of Toughness, Shape-Memory, and Self-Healing Properties.

The network structures of liquid crystal elastomers (LCEs) are crucial to impart rubbery behavior to LCEs and enable reversible actuation. Most LCEs developed to date are covalently linked, implying that the cross-links are fixed at a particular position. Herein, we report a new class of LCEs integrating polyrotaxanes (PRs) as slidable cross-links (PR-LCEs). Interestingly, the incorporation of a low loading (0.3-2.0 wt %) of the PR cross-linkers to the LCE causes a significant impact on various properties of the resulting PR-LCEs due to the pulley effect. The optimum PR loading is determined to be 0.5 wt %, at which point the toughness and damping behavior are maximized. The robust mechanical properties of the PR-LCE offers a superior actuation performance to that of the pristine LCE along with an excellent quadruple shape-memory effect. Furthermore, the incorporation of PR is useful to enhance the efficiency of shape-memory-assisted self-healing when heating above the nematic-isotropic transition.