Surface Crosslinking Research Articles

Mucins form a nanoscale physical barrier against immune cell attack.

Cancer cells construct a glycocalyx with biochemical and physical attributes that protect against immune surveillance. Whether the structural properties of the glycocalyx also physically shield cancer cells from immune recognition has not been fully resolved. Here, we utilize an interference-based imaging technique called Scanning Angle Interference Microscopy (SAIM) to accurately measure the nanoscale physical dimensions of the cellular glycocalyx. Using glycoengineering strategies and SAIM, we reveal how the surface density, glycosylation, and crosslinking of cancer-associated mucins contribute to the nanoscale material thickness of the glycocalyx, and further analyze the effect of the glycocalyx thickness on resistance to effector cell attack. We uncovered a strong reciprocal relationship between the thickness of the glycocalyx and immune cell killing. Natural Killer (NK) cell-mediated cytotoxicity exhibits a nearly perfect inverse correlation with the glycocalyx thickness of target cells regardless of the specific glycan structures present, suggesting that the physical properties of glycocalyx may be key determinants of cancer immune evasion. Changes in glycocalyx thickness as small as 10 nanometers can significantly alter susceptibility to immune cell attack. We further suggest strategies for overcoming the glycocalyx physical barrier through the cellular engineering of immune cells. These strategies include the surface display of glycocalyx-editing enzymes on the NK surface for improved penetration of the glycocalyx barrier.

Biomimetic asymmetric GO/polymer nanocomposite membrane for energy harvesting

Energy harvesting based on salinity gradients between oceans and rivers can provide a clean, stable, and continuous electric output. However, it is highly dependent on the excellent performance of biomimetic ion-selective membranes. The graphene oxide (GO) membrane, as a 2D material-based layered-structure membrane, offers the possibility of efficient salinity gradient energy conversion. However, unstable stratification in aqueous solutions and the limited number of charged functional groups make practical applications difficult. A conventional symmetric structure will also reduce the effective salinity gradient owing to ion enrichment on the low-concentration side. In this study, we pre-modified GO to create an asymmetric ion-selective membrane with opposing charges. Hyperbranched polyethyleneimine (PEI) and polyacrylic acid (PAA) as surface charge donors and crosslinkers stabilise the interlayer spacing of GO and increase charge density, achieving up to 3.4 W/m2 power density under sea water and river water. Furthermore, theoretical calculations show that membranes with asymmetric structure and opposite charges can eliminate the effect of ion enrichment on the low-concentration side, thereby avoiding power consumption. This system contributes to a further step toward the application of salinity energy conversion.

De novo synthesis of enzyme-embedded covalent organic frameworks (COFs) using deep eutectic solvent: Pushing the COF limits

Covalent organic frameworks (COFs), highly stable and porous crystalline materials, are an attractive host for embedding enzymes to protect them from harsh ex vivo conditions. However, because COF pore size must match enzyme size, larger enzyme molecules cannot be absorbed into COF matrices via COF pores. Furthermore, the COF synthesis using high temperatures, acid catalysts, and organic solvents is ineffective for the de novo construction of enzyme-embedded COFs. Herein, enzyme embedding within imine-based COFs regardless of pore dimensions is presented by pre-functionalizing the enzyme with COF aldehyde precursor and facilitating “armor-like” COF exoskeleton formation from the enzyme surface via condensation of COF aldehyde and amine precursors at ambient conditions using choline chloride/urea deep eutectic solvent as both solvent and catalyst. This de novo approach affords glucose oxidase (GOx) embedding within two kinds of COFs with pores smaller than GOx size and activity recovery of 55–62% is achieved, whereas GOx embedding into pre-synthesized COFs was not possible. According to time-dependent TEM analysis, GOx@COF morphology is dependent on enzyme and COF precursor geometry which was governed by reversible Schiff-base and Ostwald ripening. Enzyme confinement within the COF architecture, as well as chemical crosslinking of the enzyme surface with the COF exoskeleton, endows GOx@COF with excellent pH and thermo-stability, tolerance to denaturation by urea, trypsin, and organic solvent, and stable bactericidal activity over 5 recycles. The morphological structure of GOx@COF and extent of GOx cross-linking with COF precursor influence its kinetic performance. This work could open a new avenue for utilizing COFs to create a suite of stable enzyme-COF composites for various applications.

Preparation of robust and fully bio-based modified paper via mussel-inspired layer-by-layer assembly of chitosan and carboxymethyl cellulose for food packaging

A green and facile method was proposed to prepare robust and fully bio-based modified paper in this study, which involved in layer-by-layer deposition of chitosan (CS) and mussel adhesive protein-mimetic polymer (dopamine-grafted carboxymethyl cellulose, CMC-g-DA) on paper surface and subsequent oxidative cross-linking by sodium periodate. The mechanical, barrier and antibacterial properties of the cross-linked multilayer-modified paper significantly improved with the increased bilayer numbers. Compared with unmodified paper, cross-linked (CS/CMC-g-DA)6 multilayer-modified paper exhibited 71.6 % improvement in tensile strength, 69.2 % and 56.3 % decline in air and water vapor permeability, as well as above 90 % antibacterial efficiency against S. aureus and E. coli. Particularly, the cross-linked multilayer-modified paper maintained outstanding functional stability even after suffering from vigorously corrosive treatment. The obtained functional paper effectively extended the shelf-life of Agaricus bisporus to 6 days under ambient conditions. We believed that the prepared robust functional paper in this study will have promising application prospect in food packaging field.

Structural Modifications of Sodium Polyacrylate-Polyacrylamide to Enhance Its Water Absorption Rate

Superabsorbent polymers (SAPs) can absorb a large amount of water and find broad applications in various industries. There are many reports on the synthesis and structural modification techniques to improve the water absorption property of SAPs. However, we see few studies on the comparison and integration of these techniques. In this study, three structurally modified SAPs were synthesized and are evaluated for the effects of surface cross-linking, foaming, and the integration of the two modifications to improve the absorption rate and capacity of a conventional SAP. First, sodium polyacrylate-polyacrylamide was prepared as the base polymer by the aqueous solution polymerization method. Second, the base polymer was modified with surface cross-linking to enhance absorption, and a surface cross-linked SAP was obtained. Third, the base polymer was modified with foaming to obtain a foamed SAP. Lastly, the foamed SAP was modified further with surface cross-linking to obtain a foamed and surface cross-linked SAP. In comparison with the base polymer, the three synthesized SAPs were evaluated for their absorption performance. Results show that their absorption performance could be improved by the three modification processes. Specifically, the surface cross-linked SAP had the best absorption capacity under load, the foamed SAP had the highest absorption capacity of 1954 g/g, and the foamed and surface cross-linked SAP had the fastest absorption rate with an initial swelling rate of Kis = 21.94.

Developing surface molecularly imprinted cellulose acetate particles for selective recognition of S-ketoprofen enantiomers

Obtaining chiral, biologically active compounds in enantio-pure form is one of the great challenges in the pharmaceutical industry. This work prepared surface molecularly imprinted micro-beads derived from –NH2 functionalized cellulose triacetate for the enantio-selective separation of S-ketoprofen (S-KP) and enantio-separation of (±)-KP racemate. First, cellulose triacetate (CTA) micro-beads were prepared and grafted with polyacrylamide (PAm) then the amide units were converted into –NH2 groups via treatment with NaOCl (Hofmann degradation). The –NH2 functionalized CTA (C-NH2) were then loaded with the carboxylic acid-functionalized S-KP enantiomers, then imprinted upon surface cross-linking using glutaraldehyde, followed by departing the S-KP template to obtain the S-KP enantio-selective sorbent (S-KPC-NH2) finally. The polymeric materials were analyzed using Fourier-transform infrared spectroscopy (FTIR), elemental analysis, and X-ray diffraction (XRD). Also, the surface of the original CTA micro-beads, along with the obtained S-KPC-NH2 and NI-C-NH2, was visualized by the scanning electron microscope (SEM). The selective uptake of the R- and S-KP enantiomers was studied under different conditions to optimize the best removal condition. Then, the enantio-separation of the (±)-KP racemate was attempted using separation columns. The results obtained from this study indicated promising feasibility in separation and purification, especially with high-cost pharmaceuticals, which are not available in the enantio-pure form.

Development of meniscus cartilage using polycaprolactone and decellularized meniscus surface modified by gelatin, hyaluronic acid biomacromolecules: A rabbit model

The lack of vascularization in the white-red and white zone of the meniscus causes these zones of tissue to have low self-healing capacity in case of injury and accelerate osteoarthritis (OA). In this study, we have developed hybrid constructs using polycaprolactone (PCL) and decellularized meniscus extracellular matrix (DMECM) surface modified by gelatin (G), hyaluronic acid (HU) and selenium (Se) nanoparticles (PCL/DMECM/G/HU/Se), following by the cross-linking of the bio-polymeric surface. Material characterization has been performed on the fabricated scaffold using scanning electron microscopy (SEM), Fourier transforms infrared (FTIR) spectroscopy, swelling and degradation analyses, and mechanical tests. In Vitro, investigations have been conducted by C28/I2 human chondrocyte culture into the scaffold and evaluated the cytotoxicity and cell/scaffold interaction. For the in vivo study, the scaffolds were transplanted into the defect sites of female New Zealand white rabbits. Good regeneration was observed after two months. We have concluded that the designed PCL/DMECM/G/HU construct can be a promising candidate as a meniscus tissue engineering scaffold to facilitate healing.

Nanometers matter in immune evasion mediated by the cellular glycocalyx

Cancer cells construct a glycocalyx with biochemical and physical attributes that protect against immune surveillance. While it has been proposed that the glycocalyx may form a nanoscale‐thick barrier against immune cell attack, testing this possibility has proven difficult due to the challenges associated with imaging the ultrathin glycocalyx structure, particularly in live cells. In this talk, I will discuss how an imaging technique called Scanning Angle Interference Microscopy (SAIM) can be applied to accurately measure the nanoscale thickness of the cellular glycocalyx. Using SAIM and glycoengineering strategies, we reveal how the surface density, glycosylation, and crosslinking of cancer‐associated mucins contribute to the nanoscale material thickness of the glycocalyx, and further analyze the effect of the glycocalyx thickness on resistance to effector cell attack. Natural Killer (NK) cell‐mediated cytotoxicity exhibits a near perfect inverse correlation with the glycocalyx thickness of target cells regardless of the specific glycan structures present. Changes in glycocalyx thickness as small as 10 nanometers can significantly alter susceptibility to immune cell attack. Finally, I will discuss strategies for overcoming the glycocalyx barrier through cellular engineering of immune cells. These strategies include the surface display of glycocalyx‐editing enzymes on the NK surface for improved penetration of the glycocalyx barrier.

Mechanically robust, nonflammable and surface cross-linking composite membranes with high wettability for dendrite-proof and high-safety lithium-ion batteries

The separator plays a pivotal role to guarantee the safety and improve the electrochemical properties of lithium batteries. However, poor thermal stability and nonpolar surface of commercial polyolefin separator seriously restricted the development of the high-performance lithium battery. A "hydrophilic and cross-linking" strategy is proposed here to modify and enhance porous flame retardant poly(arylene ether nitrile) (PEN) polymer membrane to obtain high safety and heat resistant lithium batteries. The resultant PEN@PDA-PEI composite separator exhibits three-dimensional porous structure, superior thermal stability (no shrinkage up to 200 °C). Furthermore, the abundant polar groups (cyano group, amino group, hydroxyl group, etc.) from the composite membrane endow it with super electrolyte affinity (the contact angle is 0°) and the highly enhanced electrolyte uptake (from 400% to 618%). It is worth noting that the introduction of the PDA-PEI cross-linked structure on the surface of PEN membranes significantly improves the mechanical properties of PEN porous membrane. The composite membrane presents good lithium metal interface compatibility and high ionic conductivity (1.5 mS cm −1 ). As expected, the LiFePO 4 /Li battery based on PEN@PDA-PEI separator displays better rate and cycle performance than that of commercial polyolefin separator at elevated temperature. Significantly, the surface high-polarity and uniform pore structure of composite separators prevent the growth of lithium dendrite in cycle term, resulting an interesting 3D spherical morphology on Li metal anode. This work provides a new strategy for the preparation of high-performance and high-safety lithium-ion battery separator, it also paves a facile surface crosslinking strategy reinforce the mechanical strength of various porous membranes. • PDA-PEI crosslinking structure is used to modify the flame retardant PEN membrane for Li metal batteries. • Crosslinking structure with abundant polar groups improves the electrolyte affinity and mechanical strength of PEN separator. • The PEN@PDA-PEI separator shows good thermal and shrinkage stability at 200 °C. • Li ion distribution can be well regulated due to the uniform pore structures and the polar groups on PEN@PDA-PEI. • Batteries with PEN@PDA-PEI separator maintains stable cycling performance at high temperature.

Tannin-reinforced iron substituted hydroxyapatite nanorods functionalized collagen-based composite nanofibrous coating as a cell-instructive bone-implant interface scaffold

Bone defects account for a significant proportion of surgeries, increasing healthcare costs and complicating therapies. These factors necessitated cell-instructive bioengineering procedures to support and restore pre-existing bone function. Herein, iron-reinforced hydroxyapatite nanorod was used as an inorganic component, collagen/polycaprolactone was used as an organic component, and tannic acid was used as a surface modifier (onto nanorods), crosslinker, and functional agent. The inorganic–organic nanofibers were coated onto an implant surface using electrospinning. The nanocomposite nanostructural, contact angle, surface chemistries, thermomechanical, physicochemical, cytocompatibility, antioxidant potential, aspects of osseointegration ranging from cell adhesion, proliferation, differentiation, and bone remodeling at bone-implant zone in a rat model were studied. The results support that metal-phenolic networks on nanorods regulate interfacial interactions, nanorods cytocompatibility, antioxidant potential, and phase compatibility between organic and inorganic materials of scaffolds. The organic/inorganic nanocomposite better mimicked the bone matrix and better-supported MC3T3-E1 cell attachment, proliferation, matrix mineralization (intracellular alkaline phosphatase and calcium accumulation), and osteogenic gene expression (OPN, OCN, COL1A2, and RUNX2) to direct cell fate for bone reconstruction than its counterpart organic scaffold. The active bone formation and rebuilding of the bone-implant zone in rat models confirmed the bioactive potential of the studied nanocomposite, and it thus could be used as an interface scaffold to boost osteointegration.

Design and Manufacturing of Si-Based Non-Oxide Cellular Ceramic Structures through Indirect 3D Printing.

Additive manufacturing of Polymer-Derived Ceramics (PDCs) is regarded as a disruptive fabrication process that includes several technologies such as light curing and ink writing. However, 3D printing based on material extrusion is still not fully explored. Here, an indirect 3D printing approach combining Fused Deposition Modeling (FDM) and replica process is demonstrated as a simple and low-cost approach to deliver complex near-net-shaped cellular Si-based non-oxide ceramic architectures while preserving the structure. 3D-Printed honeycomb polylactic acid (PLA) lattices were dip-coated with two preceramic polymers (polyvinylsilazane and allylhydridopolycarbosilane) and then converted by pyrolysis respectively into SiCN and SiC ceramics. All the steps of the process (printing resolution and surface finishing, cross-linking, dip-coating, drying and pyrolysis) were optimized and controlled. Despite some internal and surface defects observed by topography, 3D-printed materials exhibited a retention of the highly porous honeycomb shape after pyrolysis. Weight loss, volume shrinkage, roughness and microstructural evolution with high annealing temperatures are discussed. Our results show that the sacrificial mold-assisted 3D printing is a suitable rapid approach for producing customizable lightweight highly stable Si-based 3D non-oxide ceramics.

Increased CO2/N2 selectivity of PTMSP by surface crosslinking.

The surface crosslinking of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes by dithiothreitol under thiol-ene click reaction conditions has yielded membranes having CO2/N2 selectivities in excess of 30 with CO2 permeances in excess of 300 GPU (gas permeation units). The simplicity of this surface crosslinking strategy together with these permeation results suggests that PTMSP that is modified in such ways could lead to useful materials for the separation of CO2/N2 from flue gas and for certain other gaseous mixtures.

Cross-linker-free sodium alginate and gelatin hydrogels: a multiscale biomaterial design framework.

Surface functionalization and cross-linking have been adopted extensively by researchers to customize hydrogel properties, especially in the last decade. The clinical translation of such biomaterials is in a poor state due to long-term toxicity, often beyond the periphery of the short-term animal studies. We endeavor to relook at the material development strategy with all FDA-approved biopolymers in their native states, like gelatin and sodium alginate, without using any functionalization and cross-linking. The fabrication of a cross-linker-free hydrogel has remained one of the main challenges in biomaterial design and requires multiscale structuring of the hydrogels. The physical properties of these hydrogels were enhanced by plasticizers (PEG and glycerol) and a monovalent salt (NaCl). An in-depth analysis suggested that PEG forms a plasticizing layer at the sodium alginate and gelatin interface and glycerol alters the overall polymer structure. The results were further complemented by different characterization methods (scattering techniques and infrared spectroscopy) and molecular dynamics simulations. The detailed microstructural analysis surfaced the enthralling integrated swelling mechanism in gelatin chains that led to high-performing hydrogels.

Multinetwork Elastomer Using Covalent Bond, Hydrogen Bond, and Clay Plane Bond.

A high-performance elastomer was obtained by a multinetworking system of a covalent bond, hydrogen bond, and clay plane bond. By taking advantage of the characteristics of each cross-linking, the thermoplastic elastomer shows excellent compression set resistance, good flowability, and high tensile properties. The hydrogen bond gives flowability due to the bond cleavage under heating. The covalent bond contributes to the low compression set by prevention of polymer chain flow. Moreover, the clay plane bond affects the tensile properties by de-localization of the entire cross-link and increase of hysteresis energy between the clay plane surface and other cross-linking points. Furthermore, the self-healing properties and high heat resistance and recyclability were also observed.

Improved separation efficiency of polyamide-based composite nanofiltration membrane by surface modification using 3-aminopropyltriethoxysilane

• Separation efficiency of PA NF membrane was improved by modification with APTES. • Modification was fulfilled via surface cross-linking and in-situ condensation. • Homogenized pore size and reduced mean pore diameter were achieved by modification. • Removal efficiency to both cationic and anionic dye aqueous solutions was improved. • Anti-fouling resistances to model foulants CTAB, HA and BSA were enhanced. Surface modification has been adopted to tune surface property of nanofiltration membrane for improved separation performance. However, it has rarely been explored to modulate membrane pore size distribution. Here, we reported a novel modification strategy combined with surface cross-linking and in-situ condensation for fabricating composite nanofiltration membrane with reduced and homogenized pore size. The strategy was fulfilled by soaking the surface of nascent polyamide-based membrane with an aqueous solution of 3-aminopropyltriethoxysilane (APTES). Membrane physico-chemical property analyses demonstrated that the hydrolyzed APTES molecules bonded onto membrane surface through amidation and esterification reactions with the residual acyl chloride groups, and chemically combined with each other through condensation reaction. Modification was found to hydrophilize membrane surface, homogenize pore size and reduce mean pore diameter. The modification under desired conditions led to an improvement in pure water permeance from 12.2 to 14.0 l/m 2 h bar, a decrease in geometric mean pore diameter from 0.71 nm to 0.63 nm, and a decline in geometric standard deviation from 1.32 to 1.23. Permeation test results showed that the APTES-modified membrane also exhibited improved removal performance to methylene blue and cresol red removal and enhanced antifouling resistances to model foulants cetyltrimethylammonium bromide, humic acid and bovine serum albumin.

Design of doxorubicin encapsulated pH-/thermo-responsive and cationic shell-crosslinked magnetic drug delivery system

The upsurge in cancer cases, such as liver cancer, has claimed millions of lives globally and has prompted the development of novel nanodrug delivery systems. These systems allow cancer drugs to be encapsulated in nanocarriers and delivered to tumor sites, and accordingly, help reduce side effects of the current chemotherapeutic treatments. Herein, we prepared nanocarriers comprising magnetic iron oxide (MIO) nanoparticles that were surface modified with crosslinked Pluronic F127 (PF127) and branched polyethylenimine (bPEI) to form MIOpoly nanocarriers. These nanocarriers were then loaded with doxorubicin (DOX) anticancer drug to form the MIOpoly-DOX complex. The nanocarriers were magnetite and possessed superparamagnetic properties. Small-angle neutron scattering (SANS) analysis indicated that the nanocarriers were thermoresponsive and spherically structured. The characteristic peaks at 1285, 1619, 2844, 2919, 2900, 2840, and 3426 cm−1, corresponding to those of CN, –NH2, –CH2, and OH–, confirmed the successful crosslinking, coating of PF127-bPEI polymers on the surface of MIO nanoparticles and DOX conjugation. The bioavailability of the nanocarriers indicated a more than 85% cell viability when using HepG2 liver cancer cells. A pH (54.8% release in 48 h; pH = 5.4) and temperature (51.0% release in 48 h; 42 °C)-dependent release of DOX was observed, displaying a Korsmeyer–Peppas kinetics model at low pH and Weibull model at high temperatures. The high DOX fluorescence observed for MIOpoly-DOX indicated a high cellular uptake enhanced by alternating magnetic field. These results suggest that MIOpoly synthesized using a combined approach of surface crosslinking and grafted with PF127-bPEI appear to offer promising properties as drug delivery system. Therefore, the nanocarriers developed in the study possess a great potential for targeted delivery and thereby circumventing the limitations of conventional chemotherapy.

3D printed hydrogel scaffolds with macro pores and interconnected microchannel networks for tissue engineering vascularization

The macro pores and interconnected microchannels in three-dimensional (3D) scaffolds are important architecture cures to support new tissues growth and vascularization. To date, the fabrication of hydrogel scaffold possessing both designed macro pores and fully interconnected microchannel (FIM) networks is still a challenge. Herein, we reported a facile method to effectively fabricate hydrogel scaffold containing designed macro pores and FIM networks by 3D printing and surface crosslinking. The surface of the printed scaffold is crosslinked, while the inner parts of the filaments are still in uncrosslinked state, after soaking the scaffold in crosslinking solution for a certain time. Then, the FIM networks are generated by removing the uncrosslinked gels from the printed filaments. The created FIM scaffold shows improved mechanical properties and structural integrity after post treatment. The channel wall with barrier function endows the scaffold with the ability of fast perfusion of liquid in the microchannels. Human umbilical vein endothelial cells are well adhered on the inner surface of the microchannels with high cell viability. In vivo study shows the excellent performance to facilitate vessels formation not only in the interface zone between scaffolds and host tissue, but also in the center of the FIM scaffolds. It also demonstrate that FIM scaffolds hold the potential capability to promote wound healing. In conclusion, the present study proposes a facile method to fabricate hydrogel scaffolds with both macro pores and FIM networks, and demonstrates their strong potential for tissue engineering application.

Multi-functional epoxy composite coating incorporating mixed Cu(II) and Zr(IV) complexes of metformin and 2,2\-bipyridine as intensive network cross-linkers exhibiting anti-corrosion, self-healing and chemical-resistance performances for steel petroleum platforms

Metal-organic network cross-linking agents are commingled with epoxy for establishing multi-functional coating system with robust resistance properties for steel protection applications in harsh atmospheres. To support this concept, the present study relates to fabrication of new mixed ligand Cu(II) and Zr(IV) complexes of metformin (MF) and 2.2′bipyridine (bpy) as coating surface cross-linking modifiers to guard the steel surface of petroleum platforms from corrosion in severe environments. CHN analysis, molar conductance, magnetic susceptibility, FT-IR, UV–Visible, 1 H NMR and TGA/DTG analysis were performed for full characterizations of the two ligands and their mixed complexes. The elemental analysis data affirmed the chemical formula of the formed complexes. Molar conductance measurements proved that the complexes were electrolytic in nature with 1:2 (metal:ligand) molar ratio. The FT-IR analysis for MF, bpy and their complexes manifested that MF and bpy chelated with metal ions as bidentate ligands through two imines (-C = NH) groups in MF and through two nitrogen of pyridine rings in bpy. The TGA/DTG analysis demonstrated the thermal stability and decomposition of the complexes. The magnetic moment measurements offered paramagnetic properties for Cu(II), μ eff = 1.70 B.M. The structure geometry survey affirmed a distorted octahedral geometry of the formed Cu(II) and Zr(IV) complexes. Epoxy coating formulations loaded with the same concentration of MF, bpy, Cu(II), and Zr(IV) compounds were applied and evaluated. Salt spray corrosion trial demonstrated that PA-DGEBA/MC-Cu coating achieved advanced corrosion mitigation demeanor at blistering size of #8, few frequency and calculated rust grade at 10. SEM morphology and EDX analysis were performed to explicate the protective performance in which PA-DGEBA/MC-Cu coated layer displayed the least Fe peak count at 2.5 without appearance of rusting. AFM microstructure of surface-modified Cu(II) epoxy coating offered the most smooth surface (Ra = 1.78 nm, Rq = 2.99 nm), with a harder matrix and perfect nonporous coating surface. Acid spot test checked the chemical resistance of these coatings and elucidated that DGEBA/MC-Cu coating achieved the highest acid resistances at Level 0 by H 2 SO 4 (96%), HNO 3 (70%) and HCl (37%) against full deterioration of blank neat epoxy at Level 3.

Water-in-water Pickering emulsions stabilized by the starch nanocrystals with various surface modifications

HypothesisUsing the platelet-like starch nanocrystals (SNCs) to stabilize emulsions is attractive because as-prepared emulsions have promising applications in cosmetics and food fields. Limited studies mainly focus on the oil-in-water system, and another important system, the water-in-water emulsions stabilized by SNCs, has not yet been unveiled. ExperimentsTwo surface modification strategies, crosslinking and acetylation, were applied to tune surface property and aggregation of SNCs, and a common all-aqueous system (dextran/poly(ethylene glycol)) was used here as template. The viscoelasticity and morphology of emulsions were studied in terms of the SNC loadings and polymer ratios. FindingsCrosslinking results in aggregation of SNCs, and the particle size increases (from 110 nm to 370 nm) with increased levels of substitution. This favors improving emulsifying ability of particles. Acetylation decreases the particle size (∼90 nm) and weakens the affinity of SNCs to the two aqueous phases, improving the emulsifying efficiency of SNCs. More intriguingly, the two emulsion systems show different phase inversion behaviors. The depletion-stabilization mechanism for the cross-linked SNCs and the diffusion-controlled mechanism for the acetylated SNCs are proposed using the emulsion viscoelasticity as probe. This study makes a comprehensive insight into the regulation of water-in-water emulsion morphology and types with the platelet-like SNCs.

Effective Enhancement of Water Absorbency of Itaconic Acid Based-Superabsorbent Polymer via Tunable Surface-Crosslinking.

A superabsorbent polymer (SAP) was synthesized by copolymerizing itaconic acid and vinyl sulfonic acid. The typically low absorbency of itaconic acid-based SAPs under mechanical loads was improved by introducing surface crosslinking. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the synthesis and surface-crosslinking reactions in the SAP. Various conditions for surface-crosslinking reactions, such as the surface-crosslinking solution, content of surface-crosslinking agent, and reaction temperature, were explored and correlated with the gel strength and absorption characteristics of the resulting SAP particles. The distilled water content in the surface-crosslinking solution strongly influenced the absorption capacity of the SAP, but this sensitivity decreased when acetone was used as a co-solvent. Itaconic acid-based SAP that was crosslinked under optimal conditions exhibited centrifuge retention capacity and absorbency under a load of 31.1 and 20.2, respectively.