Study of the synergistic influence of zwitterionic interactions and graphene oxide on water diffusion mechanism and mechanical properties in hybrid hydrogel network

Hybrid hydrogels based on n-isopropylacrylamide, zwitterionic comonomer, and graphene oxide were synthesized to study their physical and mechanical properties. The compositional variation largely influenced the swelling characteristics of the hybrid hydrogels compared to mechanical properties, i.e., elongation and compression. Additionally, Rheometric swelling measurements on the swollen hydrogels were performed until they reached equilibrium showed a very low phase angle δ indicating strong covalent network, which intrun increases with increasing content of zwitterions and GO. Swelling kinetics were studied and found to follow Fickian dynamics, albeit zwitterion-containing gels showed a peculiar 2-step swelling pattern. Interestingly, differences in the swelling mechanism are also clear for the hydrogels with 2D GO (Graphene oxide) nano-fillers from its 1D nano-filler CNTs (Carbon nanotubes). In elongation, the samples break in a brittle fashion at Hencky strains ε_max around 0.4-0.65 with the maximum stress being observed for samples with high Zw-content and 0.2% GO, which can be explained by the stress-rising properties of sharp edges of GO. In contrast, the data in compression profits from higher GO-contents as crack growth is less important in this deformation mode. This work will contribute to future composite gel applications.

3D-printed NIR-responsive shape memory polyurethane/magnesium scaffolds with tight-contact for robust bone regeneration

Patients with bone defects suffer from a high rate of disability and deformity. Poor contact of grafts with defective bones and insufficient osteogenic activities lead to increased loose risks and unsatisfied repair efficacy. Although self-expanding scaffolds were developed to enhance bone integration, the limitations on the high transition temperature and the unsatisfied bioactivity hindered greatly their clinical application. Herein, we report a near-infrared-responsive and tight-contacting scaffold that comprises of shape memory polyurethane (SMPU) as the thermal-responsive matrix and magnesium (Mg) as the photothermal and bioactive component, which fabricated by the low temperature rapid prototyping (LT-RP) 3D printing technology. As designed, due to synergistic effects of the components and the fabrication approach, the composite scaffold possesses a homogeneously porous structure, significantly improved mechanical properties and stable photothermal effects. The programmed scaffold can be heated to recover under near infrared irradiation in 60s. With 4 wt% Mg, the scaffold has the balanced shape fixity ratio of 93.6% and shape recovery ratio of 95.4%. The compressed composite scaffold could lift a 100 g weight under NIR light, which was more than 1700 times of its own weight. The results of the push-out tests and the finite element analysis (FEA) confirmed the tight-contacting ability of the SMPU/4 wt%Mg scaffold, which had a signficant enhancement compared to the scaffold without shape memory effects. Furthermore, The osteopromotive function of the scaffold has been demonstrated through a series of in vitro and in vivo studies. We envision this scaffold can be a clinically effective strategy for robust bone regeneration.

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A NIR-responsive shape memory composite scaffold fabricated by an innovative LT-RP 3D-printing technology.

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The SMPU/Mg scaffolds possess the porous structure, tight-contact and osteopromotive functions for robust bone regeneration.

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A new ‘3R’ process for bone repair: Recovered, Released, Repaired.

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Finite element analysis used for shape recovery process at the defective bone sites.

Fabrication of hydrophilic zwitterionic microspheres via inverse suspension polymerization for the enrichment of N-glycopeptides

A kind of zwitterionic microsphere was prepared via one-step inverse suspension polymerization employing 3-[N,N-dimethyl-[2-(2-methylpropyl-2-enyloxy) ethyl] ammonium] propane-1-sulfonate (MSA) and N,N-methylene bisacrylamide (BIS) as the precursors. The preparation conditions were carefully investigated and optimized by regulating the content of total monomers, ratio of MSA to BIS, ratio of water to oil, and content of stabilizer. The properties of microspheres were characterized by helium ion microscopy (HIM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N₂ adsorption/desorption measurement, and water contact angle measurement. The particle size of resulting polydisperse microspheres ranged from 15-25 μm, exhibiting high specific surface area of 138 m² g^-1. Owing to great hydrophilicity, the resulting zwitterionic microspheres could be directly used as hydrophilic interaction chromatography (HILIC) sorbent to enrich glycopeptides from biosamples without any chemical modification. A total of 19 N-glycopeptides was enriched from 10 μg of IgG digest. Besides, up to 383 N-glycopeptides and 224 N-glycosylation sites were unambiguously identified from 2 μL of human serum digest by cLC-MS/MS after enrichment with zwitterionic microspheres, indicating their great enrichment performance to N-glycopeptides. The approach of preparing hydrophilic zwitterionic microspheres contains only one synthesis reaction and is suitable for large-scale preparation.

A novel zwitterionic polymer binder with enhanced ionic conductivity for water-processable LiFePO4 cathodes

The structure of rich Li⁺ and zwitterions in LZI chains benefits the Li⁺ transport at the interfaces between the LZI and cathodes.

Zwitterionic polymer-derived nitrogen and sulfur co-doped carbon-coated Na3V2(PO4)2F3 as a cathode material for sodium ion battery energy storage

A zwitterionic polymer is used as a new nitrogen and sulfur source to synthesize N, S co-doped carbon-coated Na3V2(PO4)2F3 (NVPF-NSC) and was found to exhibit high specific discharge capacity and excellent cycle performance.

The synthesis of polyurethane with mechanical properties that are responsive to water retention states

Water-retention-state-responsive polyurethane was designed and synthesized via introducing zwitterionic sulfobetaine onto its polymer chains.

Two-Way and Multiple-Way Shape Memory Polymers for Soft Robotics: An Overview

Shape memory polymers (SMPs) are smart materials capable of changing their shapes in a predefined manner under a proper applied stimulus and have gained considerable interest in several application fields. Particularly, two-way and multiple-way SMPs offer unique opportunities to realize untethered soft robots with programmable morphology and/or properties, repeatable actuation, and advanced multi-functionalities. This review presents the recent progress of soft robots based on two-way and multiple-way thermo-responsive SMPs. All the building blocks important for the design of such robots, i.e., the base materials, manufacturing processes, working mechanisms, and modeling and simulation tools, are covered. Moreover, examples of real-world applications of soft robots and related actuators, challenges, and future directions are discussed.

A programmable, fast-fixing, osteo-regenerative, biomechanically robust bone screw

The use of a screw for repairing defected bones is limited by the dilemma between stiffness, bioactivity and internal fixation ability in current products. For polymer bone screw, it is difficult to achieve the bone stiffness and osteo-induction. Polymer composites may enhance bioactivity and mechanical properties but sacrifice the shape memory properties enormously. Herein, we fabricated a programmable bone screw which is composed of shape memory polyurethane, hydroxyapatite and arginylglycylaspartic acid to resolve the above problem. This composite has significantly improved mechanical and shape-memory properties with a modulus of 250 MPa, a shape fixity ratio of ~90% and a shape recovery ratio of ~96%. Moreover, shape fixity and recovery ratios of the produced SMPC screw in the simulative biological condition were respectively ~80% and ~82%. The produced screw could quickly recover to its original shape in vitro within 20 s leading to easy internal fixation. Additionally, the composite could support mesenchymal stem cell survival, proliferation and osteogenic differentiation in vitro tests. It also promoted tissue growth and showed beneficial mechanical compatibility after implantation into a rabbit femoral intracondyle for 12 weeks with little inflammation. Such bone screw exhibited a fast-fixing, tightened fitting, enhanced supporting and boosted bioactivity simultaneously in the defective bone, which provides a solution to the long-standing problem for bone repairing. We envision that our composite material will provide valuable insights into the development of a new generation of bone screws with good fixation and osteogenic properties. STATEMENT OF SIGNIFICANCE: The main obstacles to a wider use of a bone screw are unsatisfied stiffness, inflammatory response and screw loosening issues. Herein, we report a programmable screw with mechanically robust, bioactive and fast-fixing performances. The shape memory polymer composite takes advantage of the component in the natural bone and possesses a stable bush-like structure inside through the covalent bonding, and thus achieve significantly improved mechanical and memory properties. Based on its shape memory effect, the produced screw was proved to offer a recovery force to surroundings and promote the bone regeneration effectively. Therefore, the composite realizes our expectations on functions through structure design and paves a practical and effective way for the development of a new generation of bone screws.

A comprehensive review of the structures and properties of ionic polymeric materials

This review focuses on the mechanistic approach, the structure–property relationship and applications of ionic polymeric materials.

Liquid crystalline polyurethane composites based on supramolecular structure with reversible bidirectional shape memory and multi-shape memory effects

In this study, a novel series of supramolecular liquid crystalline (LC) polyurethane composites, named SMPU–#HOBA (# represents the molar ratio of HOBA/BINA), were successfully prepared by incorporating hexadecyloxybenzoic acid (HOBA) into pyridine-containing polyurethane (PU).

Stretchable and Self-Healing Integrated All-Gel-State Supercapacitors Enabled by a Notch-Insensitive Supramolecular Hydrogel Electrolyte

Next-generation wearable electronics are expected to endure significant deformations and mechanical damage. Therefore, self-healing stretchable electrolytes with high ionic conductivity and robust mechanical strength, which have high tolerance of deformations and spontaneously recover electrochemical properties after external damage, are necessary conditions for the realization of flexible supercapacitors. Here, a new type of zwitterionic supramolecular hydrogel cross-linked through rationally designed ionic associations and hydrogen bonds is reported (PAD/H₂SO₄). The resultant supramolecular network realizes a high ionic conductivity of 57 mS cm^-1 and unprecedented mechanical properties such as a high toughness of 35 000 J m^-2, a notch-insensitive of up to 2200% strain, and efficient instantaneous self-healing within 5 min. Acting as an electrolyte, a novel flexible supercapacitor design strategy is proposed by integrating capacitive materials directly onto the PAD/H₂SO₄ hydrogel to achieve exceptional electrochemical performance, which can be repeatable for at least 50 cutting/healing cycles. The facile and versatile strategy for the construction of the integrated all-gel-state supercapacitors with self-healing stretchable electrolytes will provide new directions for future long-life flexible devices.

Water-induced poly(vinyl alcohol)/carbon quantum dot nanocomposites with tunable shape recovery performance and fluorescence

Water-induced shape memory polymers (SMPs) show promising applications in biomedicine, biosensing, anti-counterfeiting and intelligent actuating systems. However, the dual function of shape morphing and color switching has not been achieved in the water-induced SMP system. Herein, a novel water-induced SMP with both color-switching fluorescence behavior and shape memory performance is reported. The material is fabricated by crosslinking poly(vinyl alcohol) (PVA) and pH-responsive fluorescent carbon quantum dots (CQDs). The incorporation of CQDs with PVA not only improves the shape recovery performance but also endows the material with color-switching features. To our best knowledge, such smart ability is first realized in this PVA/CQD SMP system, and this report provides a novel strategy for fabricating smart water-induced SMPs with adjustable shape recovery performance and fluorescence.

Cellulose nanofibers/polyurethane shape memory composites with fast water-responsivity

The PU/CNF nanocomposites display water-triggered fast shape memory ability, such as curling and unfolding, demonstrating tailored shape memory performance.

Shape Memory Polymers Based on Supramolecular Interactions

Shape memory polymers (SMPs), with the capability to change from one or more temporary shapes to predetermined shapes in response to an external stimulus, have attracted much interest from both academia and industries. When introducing supramolecular interactions that have been featured as dynamic and reversible into the design of novel SMPs, intriguing and unique functionalities have been engendered and thereby broaden the potential applications of the SMPs to new territories. In this review, we summarize recent progress made in SMPs based on supramolecular interactions, provide insight into the material design and shape memory mechanism, elucidate and evaluate their properties and performance, and point out opportunities and applications of SMPs.

Synthesis of zwitterionic acrylamide copolymers for biocompatible applications

In order to prepare acrylamide copolymers with non-toxicity for environment-friendly materials, a series of zwitterionic acrylamide copolymers with varying acrylamide content were synthesized with DMAPS (3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate) and acrylamide via free radical polymerization. The structural properties and cytotoxicity are carefully investigated. The results demonstrate that DMAPS- co-acrylamide copolymers contain DMAPS and acrylamide segments that form a matrix consisting of strong electrostatic interactions as well as strong hydrogen bonding. DMAPS segments exhibit negligible influence on the glass phase transition behavior, yet affect the composite’s water-contact angle. The optimum hydrophilic properties are obtained by adjusting the acrylamide content to 50 wt%. All DMAPS- co-acrylamide copolymers are measured to be non-toxic. The DMAPS segments allow for suitable contribution to the biocompatibility of the synthesized copolymer, in which copolymers containing higher DMAPS content demonstrate better biocompatibility.

Synergistic effects of zwitterionic segments and a silane coupling agent on zwitterionic shape memory polyurethanes

A novel strategy to improve shape memory properties of ZSMPUs by using a silane coupling agent. The synergistic effects of zwitterionic segments and silane coupling agents on the structure, morphology, properties were carefully investigated.

Mechanically Adaptive Nanocomposites Inspired by Sea Cucumbers

Sea cucumbers own the fascinating capability to rapidly and reversibly change the stiffness of their dermis. This mechanical morphing is achieved through a distinctive architecture of the tissue, which is composed of a viscoelastic matrix that is reinforced with rigid collagen microfibrils. Neurosecretory proteins regulate the interactions among the latter, and thereby control the overall mechanical properties of the material. This architecture and functionality have been mimicked by researchers in artificial nanocomposites that feature similar, albeit significantly simplified, structure and mechanical morphing ability. The general design of such stimulus–responsive, mechanically adaptive materials involves a low-modulus polymer matrix and rigid, high-aspect ratio filler particles, which are arranged to form percolating networks within the polymer matrix. Stress transfer is controlled by switching the interactions among the nanofibers and/or between the nanofibers and the matrix polymer via an external stimulus. In first embodiments, water was employed to moderate hydrogen-bonding interactions in such nanocomposites, while more recent examples have been designed to respond to more specific stimuli, such as a change of the pH, or irradiation with ultraviolet light. This chapter provides an overview of the general design principles and materials embodiments of such sea-cucumber inspired materials.

One-Way Multishape-Memory Effect and Tunable Two-Way Shape Memory Effect of Ionomer Poly(ethylene-co-methacrylic acid)

Reversible elongation by cooling and contraction by heating, without the need for repeated programming, is well-known as the two-way shape-memory effect (2W-SME). This behavior is contrary to the common physics-contraction when cooling and expansion when heating. Materials with such behavior may find many applications in real life, such as self-sufficient grippers, fastening devices, optical gratings, soft actuators, and sealant. Here, it is shown that ionomer Surlyn 8940, a 50-year old polymer, exhibits both one-way multishape-memory effects and tunable two-way reversible actuation. The required external tensile stress to trigger the tunable 2W-SME is very low when randomly jumping the temperatures within the melting transition window. With a proper one-time programming, "true" 2W-SME (i.e., 2W-SME without the need for an external tensile load) is also achieved. A long training process is not needed to trigger the tunable 2W-SME. Instead, a proper one-time tensile programming is sufficient to trigger repeated and tunable 2W-SME. Because the 2W-SME of the ionomer Surlyn is driven by the thermally reversible network, here crystallization and melting transitions of the semicrystalline poly(ethylene-co-methacrylic acid), it is believed that a class of thermally reversible polymers should also exhibit tunable 2W-SMEs.

A Facile Strategy to Fabricate Multishape Memory Polymers with Controllable Mechanical Properties

A facile blending strategy to fabricate multishape memory polymers (SMPs) with only one sort of phase transition material has been reported. In this work, olefin block copolymer (OBC) and styrene-b-(ethylene-co-butylene)-b-styrene (SEBS), which are both physically crosslinked, are blended with crystalline paraffin together. Due to the different interactions between polymer matrices and paraffin, the paraffin penetrated in OBC and SEBS exhibit separated melting transitions. It is quite interesting that merely paraffin distributed in OBC also shows two distinct melting transitions with enough OBC content in composites. Therefore, excellent quadruple shape memory effect can be achieved with a maximum of three melting transitions. Furthermore, through adjusting the polymer species and content, the mechanical and rheological properties can be conveniently tuned to a great extent. Compared with the reported strategies, this simple and controllable method sheds light on rapid design of multi-SMPs using inexpensive raw materials, which greatly paves the way for multi-SMPs from laboratory to factory.

Pyridine type zwitterionic polyurethane with both multi-shape memory effect and moisture-sensitive shape memory effect for smart biomedical application

The pyridine type zwitterionic SMPUs have thermal-induced dual-SMEs, triple-SMEs and quadruple-SMEs, and moisture-sensitive SMEs. Zwitterionic segments improve the biocompatibility of pyridine containing SMPUs.