Risk Factors of Hidden Blood Loss in Unilateral Biportal Endoscopic Surgery for Patients with Lumbar Spinal Stenosis.

OBJECTIVE: Unilateral biportal endoscopic (UBE) surgery has recently been used as a minimally invasive procedure for the treatment of lumbar spinal stenosis and is associated with less perioperative blood loss. However, perioperative hidden blood loss (HBL) may be neglected during UBE. This study aimed to examine the volume of HBL and discuss the influential risk factors for HBL during unilateral biportal endoscopic surgery. METHODS: From January 2022 to August 2022, 51 patients underwent percutaneous unilateral biportal endoscopic surgery for lumbar spinal stenosis at the Department of Spinal Surgery of the Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University and were enrolled in this study. The data included general indicators (age, sex and body mass index [BMI]), underlying disease (hypertension and diabetes), laboratory test results (prothrombin time [PT], activated partial thromboplastin time [APTT], fibrinogen [Fbg]), and preoperative and postoperative hematocrit and hemoglobin), related imaging parameters (severity of intervertebral disc [IVD] degeneration and soft tissue thickness of the interlaminar approach), number of operated vertebrae and operation time. Total blood loss (TBL) and HBL during surgical procedures were measured via the Gross formula. Influential factors were further analyzed by multivariate linear regression analysis and t-tests. RESULTS: The mean HBL was 257.89 ± 190.66 mL for single-operation patients and 296.58 ± 269.75 mL for two-operation patients. Patients with lower PT (p = 0.044), deeper tissue thickness (p = 0.047), and diabetes mellitus were determined to have more HBL during UBE. The operation time might also be an important factor (p = 0.047). However, sex (p = 0.265), age (p = 0.771/0.624), BMI (p = 0.655/0.664), APTT (p = 0.545/0.751), degree of degenerated IVD (p = 0.932/0.477), and hypertension (p = 0.356/0.896) were not related to HBL. CONCLUSION: This study determined the different influential factors of HBL during UBE. PT, tissue thickness, and diabetes mellitus are the independent risk factors that affect HBL incidence. Long PT may decrease the volume of HBL within a certain range. Tissue thickness and diabetes mellitus can lead to an increased volume of HBL.

Preparation of silk fibroin/hyaluronic acid composite hydrogel based on thiol-ene click chemistry. / 基于巯基-çƒ¯ç‚¹å‡»åŒ–å­¦åˆ¶å¤‡ä¸ç´ è›‹ç™½/é€æ˜Žè´¨é ¸å¤åˆæ°´å‡èƒ¶.

OBJECTIVES: To design and prepare silk fibroin/hyaluronic acid composite hydrogel. METHODS: The thiol modified silk fibroin and the double-bond modified hyaluronic acid were rapidly cured into gels through thiol-ene click polymerization under ultraviolet light condition. The grafting rate of modified silk fibroin and hyaluronic acid was characterized by 1H NMR spectroscopy; the gel point and the internal microstructure of hydrogels were characterized by rheological test and scanning electron microscopy; the mechanical properties were characterized by compression test; the swelling rate and degradation rate were determined by mass method. The hydrogel was co-cultured with the cells, the cytotoxicity was measured by the lactate dehydrogenase method, the cell adhesion was measured by the float count method, and the cell growth and differentiation on the surface of the gel were observed by scanning electron microscope and fluorescence microscope. RESULTS: The functional group substitution degrees of modified silk fibroin and hyaluronic acid were 17.99% and 48.03%, respectively. The prepared silk fibroin/hyaluronic acid composite hydrogel had a gel point of 40-60 s and had a porous structure inside the gel. The compressive strength was as high as 450 kPa and it would not break after ten cycles. The water absorption capacity of the composite hydrogel was 4-10 times of its own weight. Degradation experiments showed that the hydrogel was biodegradable, and the degradation rate reached 28%-42% after 35 d. The cell biology experiments showed that the cytotoxicity of the composite gel was low, the cell adhesion was good, and the growth and differentiation of the cells on the surface of the gel were good. CONCLUSIONS: The photocurable silk fibroin/hyaluronic acid composite hydrogel can form a gel quickly, and has excellent mechanical properties, adjustable swelling rate and degradation degree, good biocompatibility, so it has promising application prospects in biomedicine.

The Injected Foaming Study of Polypropylene/Multiwall Carbon Nanotube Composite with In Situ Fibrillation Reinforcement.

This paper explored the injection foaming process of in situ fibrillation reinforced polypropylene composites. Using polypropylene (PP) as the continuous phase, polytetrafluoroethylene (PTFE) as the dispersed phase, multi-wall carbon nanotubes (MWCNTs) as the conductive filler, and PP grafted with maleic anhydride (PP-g-MA) as the compatibilizer, a MWCNTs/PP-g-MA masterbatch was prepared by using a solution blending method. Then, a lightweight, conductive PP/PTFE/MWCNTs composite foam was prepared by means of extruder granulation and supercritical nitrogen (ScN2) injection foaming. The composite foams were studied in terms of rheology, morphological, foaming behavior and mechanical properties. The results proved that the in situ fibrillation of PTFE can have a remarkable effect on melt strength and viscoelasticity, thus improving the foaming performance; we found that PP/3% PTFE showed excellent performance. Meanwhile, the addition of MWCNTs endows the material with conductive properties, and the conductivity reached was 2.73 × 10-5 S/m with the addition of 0.2 wt% MWCNTs. This study's findings are expected to be applied in the lightweight, antistatic and high-performance automotive industry.

Novel Salt-Responsive SiO2@Cellulose Membranes Promote Continuous Gradient and Adjustable Transport Efficiency.

Continuously growing interest in the controlled and tunable transport or separation of target molecules has attracted more attention recently. However, traditional "on-off" stimuli-responsive membranes are limited to nongradient feedback, which manifests as filtration efficiency that cannot be increased or decreased gradually along with the different stimuli conditions; indeed, only the transformation of on/off state is visible. Herein, we design and fabricate a series of robust salt-responsive SiO2@cellulose membranes (SRMs) by simply combining salt-responsive poly[3-(dimethyl(4-vinylbenzyl)ammonium)propyl sulfonate] (polyDVBAPS)-modified SiO2 nanoparticles and cellulose membranes under negative-pressure filtering. The antipolyelectrolyte effect induces stretch/shrinkage of polyDVBAPS chains inside the channels and facilities the directional aperture size and surface wettability variation, greatly enhancing the variability of interfacial transport and separation efficiency. Due to the linear salt-responsive feedback mechanism, the optimal SRMs achieve highly efficient target macromolecule separation (>75%) and rapid oil/saline separation (>97%) with a continuous gradient and adjustable permeability, instead of simply an "on-off" switch. The salt-responsive factors (SiO2-polyDVBAPS) could be reversibly separated or self-assembled to membrane substrates; thus, SRMs achieved unprecedented repeatability and reusability even after long-term cyclic testing, which exceeds those of currently reported membranes. Such SRMs possess simultaneously a superfast responsive time, a controllable gradient permeability, a high gating ratio, and an excellent reusability, making our strategy a potentially exciting approach for efficient osmotic transportation and target molecule separation in a more controllable manner.

Click-Chemistry Approach toward Antibacterial and Degradable Hybrid Hydrogels Based on Octa-Betaine Ester Polyhedral Oligomeric Silsesquioxane.

An efficient process for the synthesis of degradable hydrogels containing octa-betaine ester polyhedral oligomeric silsesquioxane (POSS) through efficient thiol-ene and Menschutkin click reactions was developed. The hydrogels exhibited a yield strength of 0.36 MPa and a compressive modulus of 4.38 MPa and displayed excellent flexibility as well as torsion resistance. Antibacterial efficacy of hydrogels (and degradation products) was evaluated using Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). Efficacy was found to increase with the concentration of cetyl chloroacetate (CCA) in the hydrogel network, reaching 93% and 99% for Escherichia coli and Staphylococcus aureus, respectively. Degradation of hydrogels was observed in weak alkali conditions (pH = 8) and at physiological conditions (pH = 7.4). The degradation time of the hydrogels could be finely tuned by variation of the CCA content in the hydrogel and environmental stimulus. The tunable degradation behavior under physiological conditions combined with high antibacterial efficacy could render the presented materials interesting for tissue engineering applications.

Adjustable and ultrafast light-cured hyaluronic acid hydrogel: promoting biocompatibility and cell growth.

Bio-sourced hydrogels are attractive materials for diagnosing, repairing and improving the function of human tissues and organs. However, their mechanical strength decreases with an increase in water content. Furthermore, it is challenging to mold these hydrogels with high precision, which significantly limits their applications. Herein, we modified a biocompatible and biodegradable material, hyaluronic acid, with methacrylic anhydride and then cured it with a four-arm star structure cross-linking agent under ultraviolet light. The hyaluronic acid hydrogel was finally cured within 15 s with an adjustable cross-linking degree. The results demonstrated that the developed gel maintained good mechanical strength with a water content of 90%, while achieving micropatterns at a precision of 20 µm. The biological experiments showed that it could effectively promote the release of vascular endothelial growth factor (VEGF), which contributed to promoting cell growth, and has favorable biocompatibility. Overall, this hyaluronic acid hydrogel is a promising biomedical material with high forming accuracy, excellent mechanical properties, and favorable biocompatibility, which indicate its potential value in a variety of tissue engineering and biomedical applications.

GO@Fe3O4@CuSilicate Composite with a Hierarchical Structure: Fabrication, Microstructure, and Highly Electromagnetic Shielding Performance.

Two nanocomposites with a hierarchical structure (GO@CuSilicate@Fe3O4 and GO@Fe3O4@CuSilicate) were fabricated in this paper. These as-synthesized nanocomposites were analyzed for their structural, compositional, and morphological features by X-ray diffraction, scanning electron microscopy (SEM), Raman spectroscopy, and Brunauer-Emmett-Teller methods. SEM images showed that both nanocomposites had a core-shell structure, and their shells were composed of CuSilicate nanoneedle arrays. Further, their total electromagnetic shielding efficiency was measured and compared in a wide frequency range of 8-12 GHz (X-band). Because of the "antenna" role of CuSilicate nanoneedle arrays and the polarization at the interface between graphene oxide (GO) and Fe3O4, GO@Fe3O4@CuSilicate showed higher electromagnetic shielding performance than that of GO@CuSilicate@Fe3O4. With 1 mm thickness, GO@Fe3O4@CuSilicate showed a high electromagnetic shielding efficiency (over 40 dB) in the whole X-band (8.2-12.4 GHz) and reached a maximum value (41.8 dB) at 8.2 GHz. Its total electromagnetic shielding efficiency was mainly contributed by absorption rather than reflection. This study provided an idea for the structural design of high-performance electromagnetic shielding materials in the GHz frequency range (X band).

Design of salt-responsive and regenerative antibacterial polymer brushes with integrated bacterial resistance, killing, and release properties.

The development of smart materials and surfaces with multiple antibacterial actions is of great importance for both fundamental research and practical applications, but this has proved to be extremely challenging. In this work, we proposed to integrate salt-responsive polyDVBAPS (poly(3-(dimethyl(4-vinylbenzyl) ammonio)propyl sulfonate)), antifouling polyHEAA (poly(N-hydroxyethyl acrylamide)), and bactericidal TCS (triclosan) into single surfaces by polymerizing and grafting polyDVBAPS and polyHEAA onto the substrate in a different way to form two types of polyDVBAPS/poly(HEAA-g-TCS) and poly(DVBAPS-b-HEAA-g-TCS) brushes with different hierarchical structures, as confirmed by X-ray photoelectron spectroscopy (XPS), atom force microscopy (AFM), and ellipsometry. Both types of polymer brushes demonstrated their tri-functional antibacterial activity to resist bacterial attachment by polyHEAA, to release ∼90% of dead bacteria from the surface by polyDVBAPS, and to kill ∼90% of bacteria on the surface by TCS. Comparative studies also showed that removal of any component from polyDVBAPS/poly(HEAA-g-TCS) and poly(DVBAPS-b-HEAA-g-TCS) compromised the overall antibacterial performance, further supporting a synergistic effect of the three compatible components. More importantly, the presence of salt-responsive polyDVBAPS allowed both brushes to regenerate with almost unaffected antibacterial capacity for reuse in multiple kill-and-release cycles. The tri-functional antibacterial surfaces present a promising design strategy for further developing next-generation antibacterial materials and coatings for antibacterial applications.

Electric Assisted Salt-Responsive Bacterial Killing and Release of Polyzwitterionic Brushes in Low-Concentration Salt Solution.

Polyzwitterionic brushes with strong antipolyelectrolyte effects have shown great potential as versatile platforms for the development of switchable friction/lubrication and bacterial absorption/desorption surfaces. However, the surface property switches of these brushes are usually triggered by high salt concentrations (>0.53 M), thereby greatly limiting their applications in biological fields where the salt concentration for mammals is ?0.15 M. To solve this problem, an electric field was used to assist the salt-responsive process of the polyzwitterionic brushes to achieve bacterial release at low concentrations of the salt solution. Briefly, poly(3-(dimethyl (4-vinylbenzyl) ammonium) propyl sulfonate) (polyDVBAPS) brushes grafted on ITO surfaces were prepared by surface initiated atom transfer radical polymerization. The bacterial release of this surface was conducted under an electric field, where anions were migrated and enriched around the brush-grafted ITO surface as anode. The local high concentration ion led to the conformation change of the brush and release of the attached bacteria. The effect of salt type, salt concentration, electric field strength, and conducting time on the bacterial release properties were investigated. The results indicated that under an electrical field of 3 V/mm, polyDVBAPS showed release capacities of ?93% for E. coli and ?81% for S. aureus in 0.12 M NaCl electrolyte solution. Furthermore, by the introduction of a bactericidal agent, i.e., Triclosan (TCS), an antibacterial surface with dual functions of killing and release was fabricated. This surface could kill ?90% and release 95% of attached E. coli in a 0.12 M NaCl solution by the application of a 3 V/mm electric field. This work demonstrated the feasibility of triggering a salt-responsive behavior of polyzwitterionic at low salt concentration by assistance of electric field, which would greatly extend the applications of polyzwitterionic, in particular in biological applications.

One-Pot and One-Step Fabrication of Salt-Responsive Bilayer Hydrogels with 2D and 3D Shape Transformations.

Bilayer hydrogels are one of the most promising materials for use as soft actuators, artificial muscles, and soft robotic elements. Therefore, the development of new and simple methods for the fabrication of such hydrogels is of particular importance for both academic research and industrial applications. Herein, a facile, one-pot, and one-step methodology was used to prepare bilayer hydrogels. Specifically, several common monomers, including N-isopropyl acrylamide, acrylamide, and N-(2-hydroxyethyl)acrylamide, as well as two salt-responsive zwitterionic monomers, 3-(1-(4-vinylbenzyl)-1H-imidazol-3-ium-3-yl)propane-1-sulfonate (VBIPS) and dimethyl-(4-vinylphenyl)ammonium propane sulfonate (DVBAPS), were chosen and employed with different combinations and ratios to understand the formation and structural tunability of the bilayer hydrogels. The results indicated that a salt-responsive zwitterionic-enriched copolymer, which could precipitate from water, plays a dominant role in the formation of the bilayer structure and that the ratio between the common monomer and the zwitterionic monomer had a significant effect on the structure. Due to the salt-responsive properties of polyVBIPS and polyDVBAPS, the resultant bilayer hydrogels exhibited excellent bidirectional bending properties in response to the salt solution. With the optimal monomer pair and ratio determined, the bend of the hydrogel could be reversed from ∼-360 to ∼266° in response to a switch between water and a 1.0 M NaCl solution. Additionally, this method was further used to fabricate small-scaled patterns with structural and compositional distinction in two-dimensional hydrogel sheets. These two-dimensional hydrogel sheets exhibited complex and reversible three-dimensional shape transformations due to the different bending behaviors of the patterned hydrogel stripes under the action of an external stimulus. This work provides greater insight into the mechanism of the one-step, one-pot method fabrication of bilayer hydrogels, demonstrates the ability of this method for the preparation of small-scale patterns in hydrogel sheets to endow the complex with a three-dimensional shape transformation capability, and hopefully opens up a new pathway for the design and fabrication of smart hydrogels.

Extrusion Foaming of Lightweight Polystyrene Composite Foams with Controllable Cellular Structure for Sound Absorption Application.

Polymer foams are promising for sound absorption applications. In order to process an industrial product, a series of polystyrene (PS) composite foams were prepared by continuous extrusion foaming assisted by supercritical CO2. Because the cell size and cell density were the key to determine the sound absorption coefficient at normal incidence, the bio-resource lignin was employed for the first time to control the cellular structure on basis of hetero-nucleation effect. The sound absorption range of the PS/lignin composite foams was corresponding to the cellular structure and lignin content. As a result, the maximum sound absorption coefficient at normal incidence was higher than 0.90. For a comparison, multiwall carbon nanotube (MWCNT) and micro graphite (mGr) particles were also used as the nucleation agent during the foaming process, respectively, which were more effective on the hetero-nucleation effect. The mechanical property and thermal stability of various foams were measured as well. Lignin showed a fire retardant effect in PS composite foam.

Super Hydrophilic Semi-IPN Fluorescent Poly(N-(2-hydroxyethyl)acrylamide) Hydrogel for Ultrafast, Selective, and Long-Term Effective Mercury(II) Detection in a Bacteria-Laden System.

Convenient, low-cost chemosensors for hazardous mercury ion detection have been receiving more and more attention in recent studies. However, most of these practical studies are based on an ideal sterile detecting atmosphere and ignore the role of bacteria in actual Hg(II) analytes. Herein, we demonstrate a new type of hydrophilic semi-IPN fluorescent polyHEAA hydrogel chemosensors fabricated by UV polymerization in situ interpenetrating fluorescent polymer PA-NDBCB with a polyHEAA network. Because of specific intermolecular interaction, i.e., hydrogen bonding between hydrophilic fluorescent polymer and polyHEAA matrix comprising a distinct semi-IPN structure, the mechanical property of bulk fluorescent hydrogels can be greatly improved over that of pure polyHEAA hydrogels. Moreover, the design of the hydrogel chemosensors rely on the highly efficient cyclization reaction between Hg(II) ions and the thiourea moieties that induce a visible "green-to-blue" fluorescence color change. On account of the hydrophilic porous structures, these hydrogel chemosensors achieve ultrafast, sensitive, selective Hg(II) detection (detection limit of 0.067 µM) and enable facile ratiometric actual detection in real-world aqueous system. Notably, they maintain fluorescence emission and detection property even under long-term coculture in a complex E. coli bacteria-laden environment. This novel strategy could inspire future construction of soft interfaces/fluorescent apparatus for hazardous Hg(II) detection in a complex real-world system.

Synthesis and characterization of a novel ruthenium(ii) trisbipyridine complex magnetic nanocomposite for the selective oxidation of phenols.

Anchoring ruthenium(ii) trisbipyridine complex [Ru(Bpy)3]2+ into a magnetic dendritic fibrous silica nanostructure produces an unprecedented strong nanocatalyst, FeNi3/DFNS/[Ru(Bpy)3]2+. Impressive oxidation of phenols to 1,4-benzoquinones catalyzed by FeNi3/DFNS/[Ru(Bpy)3]2+ is obtained in acetonitrile and water solution with molecular dioxygen as oxidant. Exclusively, apparently inert phenols such as phenol itself and mono-alkyl-substituted phenols are impressively oxidized to produce 1,4-benzoquinones through activation of the C-H bond in the position para to the carbon-oxygen bond under mild conditions. In addition, the production of industrially significant quinones that are known intermediates for vitamin combinations is investigated and studied FeNi3/DFNS/[Ru(Bpy)3]2+ magnetic nanoparticles were produced, and their properties were investigated by AFM, FTIR, XRD, TGA, SEM, TEM, and VSM.

Dual Salt- and Thermoresponsive Programmable Bilayer Hydrogel Actuators with Pseudo-Interpenetrating Double-Network Structures.

Development of smart soft actuators is highly important for fundamental research and industrial applications but has proved to be extremely challenging. In this work, we present a facile, one-pot, one-step method to prepare dual-responsive bilayer hydrogels, consisting of a thermoresponsive poly( N-isopropylacrylamide) (polyNIPAM) layer and a salt-responsive poly(3-(1-(4-vinylbenzyl)-1 H-imidazol-3-ium-3-yl)propane-1-sulfonate) (polyVBIPS) layer. Both polyNIPAM and polyVBIPS layers exhibit a completely opposite swelling/shrinking behavior, where polyNIPAM shrinks (swells) but polyVBIPS swells (shrinks) in salt solution (water) or at high (low) temperatures. By tuning NIPAM:VBIPS ratios, the resulting polyNIPAM/polyVBIPS bilayer hydrogels enable us to achieve fast and large-amplitude bidirectional bending in response to temperatures, salt concentrations, and salt types. Such bidirectional bending, bending orientation, and degree can be reversibly, repeatedly, and precisely controlled by salt- or temperature-induced cooperative swelling-shrinking properties from both layers. Based on their fast, reversible, and bidirectional bending behavior, we further design two conceptual hybrid hydrogel actuators, serving as a six-arm gripper to capture, transport, and release an object and an electrical circuit switch to turn on-and-off a lamp. Different from the conventional two- or multistep methods for preparation of bilayer hydrogels, our simple, one-pot, one-step method and a new bilayer hydrogel system provide an innovative concept to explore new hydrogel-based actuators through combining different responsive materials that allow us to program different stimuli for soft and intelligent materials applications.

Morphological Structure, Rheological Behavior, Mechanical Properties and Sound Insulation Performance of Thermoplastic Rubber Composites Reinforced by Different Inorganic Fillers.

The application area of a sound insulation material is highly dependent on the technology adopted for its processing. In this study, thermoplastic rubber (TPR, polypropylene/ethylene propylene diene monomer) composites were simply prepared via an extrusion method. Two microscale particles, CaCO3 and hollow glass microspheres (HGW) were chosen to not only enhance the sound insulation but also reinforced the mechanical properties. Meanwhile, the processing capability of composites was confirmed. SEM images showed that the CaCO3 was uniformly dispersed in TPR matrix with ~3 µm scale aggregates, while the HGM was slightly aggregated to ~13 µm scale. The heterogeneous dispersion of micro-scale fillers strongly affected the sound transmission loss (STL) value of composites. The STL values of TPR composites with 40 wt % CaCO3 and 20 wt % HGM composites were about 12 dB and 7 dB higher than that of pure TPR sample, respectively. The improved sound insulation performances of the composites have been attributed to the enhanced reflection and dissipate sound energy in the heterogeneous composite. Moreover, the mechanical properties were also enhanced. The discontinued sound impedance and reinforced stiffness were considered as crucial for the sound insulation.

Integration of antifouling and antibacterial properties in salt-responsive hydrogels with surface regeneration capacity.

The development of new antimicrobial materials and strategies is of importance for many biomedical and industrial applications. In this work, we report a new strategy to integrate distinct antimicrobial, antifouling, and stimuli-responsive properties into a single hydrogel to realize bacteria resistance, killing, and releasing functions. To achieve this design, we conjugated salt-responsive anti-polyelectrolyte polyDVBAPS (poly(3-(dimethyl(4-vinylbenzyl)ammonio)propyl sulfonate)) with antifouling polyHEAA (poly(N-hydroxyethyl acrylamide)) and antimicrobial AgNPs (silver nanoparticles) to form a hybrid hydrogel of polyDVBAPS-g-polyHEAA@AgNPs, among which polyHEAA functions as a general antifouling background to prevent bacteria adsorption on the surface, AgNPs act as antimicrobial agents to kill bacteria on the surface, and polyDVBAPS uses its unique salt-responsive, anti-polyelectrolyte property to release adherent bacteria from the surface. In this design, polyDVBAPS-g-polyHEAA@AgNPs hydrogels not only effectively resist bacteria attachment and kill the adherent bacteria, but also regenerate the antifouling surface of the hydrogel by releasing the adhered bacteria to keep the surface free from bacteria. The polyDVBAPS-g-polyHEAA@AgNPs hydrogels exhibited high surface resistance to bacteria adsorption (<106 cells per cm2) for up to 4 days, high antibacterial activity by killing ∼99% of attached bacteria of both E. coli and S. aureus, and surface regeneration ability by releasing >96% of adherent live or dead bacteria from the surface upon a simple treatment of 1.0 M NaCl solution for 10 min. Upon the release of AgNPs, AgNPs were reloaded into the hydrogel again to achieve multiple antifouling, bactericidal, and regenerative properties. This work demonstrates a new design for a new multifunctional hydrogel to effectively achieve antimicrobial, antifouling, and surface regeneration properties, making this hydrogel very promising for antimicrobial applications.

Bioinspired pH-Sensitive Surface on Bioinert Substrate.

Polydimethylsiloxane (PDMS) is a common biomaterial with excellent properties. However, its inherent hydrophobicity impedes cell growth and differentiation. PDMS is an intrinsically inert material, which limits its applications to specific scenarios where responsive materials are needed. Dopamine can easily adhere to various substrate surfaces through noncovalent and covalent interactions. In this work, a bioinert PDMS surface was modified into a bioactive surface by biocompatible and pH-sensitive polydopamine (PDA). The binding of PDA and PDMS in different forms was verified by the typical scanning electron microscopy (SEM) and atomic force microscope (AFM). By PDA film modification, the contact angle of PDMS was significantly reduced. Hydrophobicity was achieved by PDA nanosphere (PDA NS) modification. PDA-modified PDMS was also found to be pH-sensitive, as validated by contact angle measurement, macroscopic friction test, and protein adsorption. Compared to an unmodified surface, the PDA significantly improved cell adhesion, proliferation and spreading. We came to a conclusion that the surface roughness of PDA-modified PDMS had little effect on cell growth and the cytocompatibility of the materials was mainly determined by the surface chemical properties. Our results further validated that PDA/PDMS is pH-sensitive and can effectively promote cell growth and proliferation.

Enhanced energy density and thermal conductivity in poly(fluorovinylidene-co-hexafluoropropylene) nanocomposites incorporated with boron nitride nanosheets exfoliated under assistance of hyperbranched polyethylene.

Polymer dielectric film with a large dielectric constant, high energy density and enhanced thermal conductivity are of significance for the development of impulse capacitors. However, the fabrication of polymer dielectrics combining high energy density and thermal conductivity is still a challenge at the moment. Here we demonstrate the facile exfoliation of hexagonal boron nitride nanosheets (BNNSs) in common organic solvents under sonication with the assistance of hyperbranched polyethylene (HBPE). The noncovalent CH-π interactions between the nanosheets and HBPE ensure the dispersion of BNNSs in organic solvents with high concentrations, because of the highly branched chain structure of HBPE. Subsequently, the resultant BNNSs with a few defects are distributed uniformly in the poly(fluorovinylidene-co-hexafluoropropylene) (P(VDF-HFP)) nanocomposite films prepared via simple solution casting. The BNNS/P(VDF-HFP) nanocomposite exhibits outstanding dielectric properties, high energy density and high thermal conductivity. The dielectric constant of the 0.5 wt% nanocomposite film is 35.5 at 100 Hz with an energy density of 5.6 J cm-3 at 325 MV m-1 and a high charge-discharge efficiency of 79% due to the depression of the charge injection and chemical species ionization in a high field. Moreover, a thermal conductivity of 1.0 wt% nanocomposite film reaches 0.91 W·m-1 · K-1, which is 3.13 times higher than that of the fluoropolymer matrix. With dipole accumulation and orientation in the interfacial zone, lightweight, flexible BNNS/P(VDF-HFP) nanocomposite films with high charge-discharge performance and thermal conductivity, exhibit promising applications in relatively high-temperature electronics and energy storage devices.

Structural Dependence of Salt-Responsive Polyzwitterionic Brushes with an Anti-Polyelectrolyte Effect.

Some polyzwitterionic brushes exhibit a strong "anti-polyelectrolyte effect" and ionic specificity that make them versatile platforms to build smart surfaces for many applications. However, the structure-property relationship of zwitterionic polymer brushes still remains to be elucidated. Herein, we aim to study the structure-dependent relationship between different zwitterionic polymers and the anti-polyelectrolyte effect. To this end, a series of polyzwitterionic brushes with different cationic moieties (e.g., imidazolium, ammonium, and pyridinium) in their monomeric units and with different carbon spacer lengths (e.g., CSL = 1, 3, and 4) between the cation and anion were designed and synthesized to form polymer brushes via the surface-initiated atom transfer radical polymerization. All zwitterionic brushes were carefully characterized for their surface morphologies, compositions, wettability, and film thicknesses by atomic force microscopy, contact angle measurement, and ellipsometry, respectively. The salt-responsiveness of all zwitterionic brushes to surface hydration and friction was further examined and compared both in water and in salt solutions with different salt concentrations and counterion types. The collective data showed that zwitterionic brushes with different cationic moieties and shorter CSLs in salt solution induced higher surface friction and lower surface hydration than those in water, exhibiting strong anti-polyelectrolyte effect salt-responsive behaviors. By tuning the CSLs, cationic moieties, and salt concentrations and types, the surface wettability can be changed from a highly hydrophobic surface (∼60°) to a highly hydrophilic surface (∼9°), while interfacial friction can be changed from ultrahigh friction (µ ≈ 4.5) to superior lubrication (µ ≈ 10-3). This work provides important structural insights into how subtle structural changes in zwitterionic polymers can yield great changes in the salt-responsive properties at the interface, which could be used for the development of smart surfaces for different applications.

Preparation of carbon-based hybrid particles and their application in microcellular foaming and flame-retardant materials.

Polymeric microcellular foams with high strength and light weight are very important for industrial applications. However, regulating their cell structure and their weak flame retardancy are problematic. We designed single-arm POSS-based ionic liquids ([bel-POSS][PF6]), and constructed hybrid composites based on physical interaction between ionic liquids and carbon-based materials in PS microcellular foaming. Ionization of bel-POSS could result in a quaternary ammonium reaction and ion-exchange reaction, and the carbon materials exhibit good dispersion through blending. The prepared hybrid composites showed high CO2 adsorption. Conical calorimeter tests showed that PS composite materials could reduce the heat release rate, total heat release, toxic gases (CO2 and CO) release, and amount of smoke generated. These carbon materials could affect PS micropore structure, including the cell diameter and density. Upon addition of 5 wt% of carbon materials, the hole diameter decreased by >50%, and the hole density increased nearly ten folds.