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The field of biocatalysis is expanding owing to the increasing demand for efficient low-cost green chemical processes. However, a feasible strategy for achieving product separation, enzyme recovery, and high catalytic efficiency in biocatalysis remains elusive. Herein, we present thermoresponsive Pickering high internal phase emulsions (HIPEs) as controllable scaffolds for efficient biocatalysis; these HIPEs demonstrate a transition between emulsification and demulsification depending on temperature. Ultra-high-surface-area Pickering HIPEs were stabilized by Candida antarctica lipase B immobilized on starch particles modified with butyl glycidyl ether and glycidyl trimethyl ammonium chloride, thus simplifying the separation and reuse processes and significantly improving the catalytic efficiency. In addition, the switching temperature can be precisely tuned by adjusting the degree of substitution of the modified starches to meet the temperature demands of various enzymes. We believe that this system provides a green platform for various interfacial biocatalytic processes of industrial interest.

Green technologies, environmental protection, and sustainable development are some of the most important issues in today's world. Herein, a low-cost, environment-friendly, and sustainable strategy for fabricating a superwettable porous polymer sphere is reported for the treatment of various kinds of oil-in-water and water-in-oil emulsions. A thermoresponsive 2-hydroxy-3-butoxypropyl starch (HBPS) was synthesized as a representative natural material by simple chemical modification with butyl glycidyl ether, and was used as an effective stabilizer for Pickering emulsion formation. The state of the resulting emulsions could be switched by adjusting the temperature, with emulsification at low temperatures (lower than the lower critical solution temperature (LCST) of HBPS) and demulsification at high temperatures (higher than the LCST of HBPS). Based on this temperature-switchable emulsion system, a straightforward recyclable Pickering emulsion polymerization was designed and used for the fabrication of polymer spheres. A Pickering emulsion polymerization is an emulsion polymerization process in which the colloidal stability of the produced polymer dispersion is supported by solid particles. The distinct superwettability (superlipophilicity and under-oil superhydrophobicity), porosity, and small pore size of polymer spheres achieved resulted in an excellent performance in separating oil-in-water and water-in-oil emulsions with separation efficiencies over 99.9%. This work not only achieved a highly energy-efficient green recyclable Pickering emulsion polymerization system and provided a valuable strategy for the green synthesis process but also resulted in the fabrication of novel spheres with outstanding properties for separating various types of emulsions, with attractive prospects for advanced applications in separating complex emulsions, wastewater treatment, and environmental protection.

There is a pressing need around the world to develop novel functional biodegradable materials to separate oil/water mixtures and emulsions completely. Recently, superhydrophilicity and underwater superoleophobicity materials have been attracted attention due to their high efficiency in oil/water separation. However, it is still a challenge to prepare materials that combine oil/water separation and water purification in an environment-friendly way. In this work, biodegradable starch-based nanospheres (SNPs) coated filter paper was prepared in a low-cost, simple, and environmentally friendly manner. The SNPs coating could not only help to change the wettability of the substrate material but also build the hierarchical micro and nano structures which are conducive to separation and purification process. After modification by coating SNPs, the filter paper exhibited excellent performance in a wide range of oil/water mixtures or emulsions separation and the wettability of the filter paper could be regulated by adjusting the pH value. The modified filter paper presented good recyclability after several separation process. Furthermore, the as-prepared filter paper could also remove water-soluble contaminants during the oil/water separation process, thus realizing to combine separation and purification process in one single step. This biodegradable starch-based separating material with good separation performance, stability and recyclability has significant application potential in practical separation and purification process.

Pickering high internal phase emulsions (HIPEs) stabilized solely by bioderived starch-based particles hold potential for application in the food and pharmaceutical fields. This paper reports the use of a thermoresponsive 2-hydroxy-3-butoxypropyl starch (HBPS) particle as a representative natural biocompatible material for use as an effective stabilizer for HIPE formation. HBPS is synthesized by using butyl glycidyl ether as a hydrophobic reagent to change the hydrophobic–hydrophilic balance of starch, and then starch-based particles are fabricated by a simple nanoprecipitation procedure. The size of particles increased with an increase in temperature, and the particles are essentially monodisperse with a PDI of about 0.1 when the temperature was above 15 °C. These HBPS particles were subsequently used as an effective stabilizer to fabricate stable oil-in-water (o/w) Pickering HIPEs with an internal phase volume of 80% at different stabilizer concentrations. The results demonstrated that increasing the particle concentration is conducive to the formation of stable Pickering HIPEs with greater stiffnesses. In addition, the nutraceutical material (β-carotene) was encapsulated into HIPEs and in vitro release experiments revealed that the release in this system can be controlled by adjusting the temperature.

To realize intelligent and low-cost protective materials, the development of compounds with smart stress-responsive properties and self-healing abilities over a wide temperature range is a major research goal. In this study, a series of impact hardening polymers (IHPs) with stress-responsive properties and self-healing ability in low temperature were synthesized via the condensation copolymerization of silicone polymers with various chain lengths and boron contents. The results of rheological analysis indicate that the IHPs have self-healing ability at low temperatures (healing times of less than 30 h and healing efficiencies better than 80% at −25 °C). Moreover, the relative shear stiffening effect (RSTe), which describes the stress-responsive ability of the IHP, exceeded 2000. In addition, the self-healing mechanism of IHP was investigated by Fourier transform infrared spectroscopy microscopy and pulsed 1H-NMR measurements. The results suggested that reversible dynamic cross-linking arising from the boron compound and the reduction in the threshold entanglement density owing to the longer length of the flexible polymeric backbone is crucial to impart low-temperature self-healing ability and stress-responsive properties to IHP.

Inverse Pickering emulsions stabilized by naturally derived particles are of interesting during the past decade. In this study, starch-based nanoparticles were used as a particulate emulsifier to stabilize a w/o Pickering emulsion. The effects of particle concentration and oil volume fraction on the emulsion type and stability were investigated in detail. Catastrophic phase inversion from o/w to w/o emulsions occurred at a volume fraction of oil of 0.3-0.4, without altering the particle wettability. Further, a linear relation existed between the average droplet diameter and total amounts of starch-based nanoparticles. The obtained starch-based nanoparticles also served as a Pickering stabilizer to conduct a w/o Pickering polymerization. Raspberry-like thermoresponsive starch-poly(N-isopropyl acrylamide) nanocomposites with a well-defined structure were synthesized.

Adsorptive membranes offer an effective mode to remove heavy metal ions from contaminated water, due to the synergies made possible by low-cost, high-affinity adsorbents and highly scalable filtration in one system. However, the development of adsorptive membranes is hampered by their instability in the aqueous phase and low binding affinity with a broad spectrum of heavy metals in a reasonable flux. Herein, a regenerated cellulose support membrane is strongly grafted with stable and covalent-bonded polyelectrolyte active layers synthesized by a reactive layer-by-layer (LBL) assembly method. The LBL assembled layers have been successfully tested by scanning electron microscopy, Fourier-transform infrared spectroscopy and X-ray photo-electron spectroscopy. The covalent bonding provides the membrane with long-term stability and a tunable water flux compared to a membrane assembled by electrostatic bonding. The maximum adsorption capacity of the membrane active layers can reach up to 194 mg/g, showing more efficient adsorption at lower heavy metal concentration and higher pH value of feed solution. The membrane can remove multiple ions, such as Cu, Pb, and Cd, by adsorption and is easy to be regenerated and recovered. The strong covalent bonding can extend the membrane lifetime in water purification to remove multiple heavy metals at high efficiency.

In this work, poly(methacrylatoethyl trimethyl ammonium chloride -co-acrylamide)/diatomite composite flocculant was synthesized via in situ polymerization in aqueous solution and applied in waste water treatment. The structure of composite flocculants was characterized by FT-IR, 1HNMR and XRD, TGA and viscometer. Herein, the apparent viscosity of composite flocculants was employed as comparison standard of their performance to evaluate the influence of the reaction parameters, such as monomer feeding ratio, diatomite mass fraction and polymerization temperature, etc. on their flocculation performance. And based on the above investigations, the optimum synthesis condition could be found. By comparing flocculation properties of composite flocculants with that of the conventional cationic flocculant, the dosage of composite flocculant that could make the transmittance of treated waste water exceed 95 % was only 7.5 ppm which was far lower than that of conventional flocculant (60–90 ppm). Meanwhile, the settling time was lower than 5 s which was similarly to that of conventional flocculant. Finally, the conclusion was that the composite flocculant owned higher absorption capacity and larger chain extending space than those of conventional linear flocculant due to the introduction of diatomite as backbone, which could make linear polymer chains free from entanglement and improve the flocculation capacity notably.

Nonspherical colloidal particles with various geometries and different compositions have attracted tremendous attention and been widely researched. The preparation of polymer colloidal particles with controlled shapes by seeded polymerization is recognized as the most promising technique owing to the precise control of various morphologies and using non-cross-linked seed particles are of particular interest. Seeds particles derived from natural biopolymers are seldom applied. Hence, non-cross-linked starch-based seed could be used to fabricate the anisotropic particles by soap-free seed polymerization. Non-cross-linked starch-based seed particles were prepared by a nanoprecipitation method. Starch/polystyrene composite colloidal particles with shape-tunable were fabricated by soap-free seeded polymerization using starch-based seed. The effect of the polymerization time, monomer feed ratio and seed type were investigated. The seed particles with a single- or multi-hole structure were obtained after swelling with styrene. The resulting particles including golf-like, raspberry-like, octahedron-like and snowman-like structures, was fabricated on the polymerization process. This study firstly reports that the morphology of composite particles from golf-like to snowman-like at high monomer feed ratio using starch-based seed. At low monomer feed ratio, raspberry-like particles were obtained by surface nucleation increasing process. In addition, seed type also effect the morphology of composite particles.

Surface wettability, one of the most important parameters for oil–water separation, depends on the chemical composition and surface roughness of a material. Herein, the Pickering emulsion template method is proposed to control the surface wettability of polymer microspheres. Upon the dispersion of modified diatomite particles in the aqueous phase, a superhydrophobic surface was formed on the polymer microspheres via Pickering emulsion polymerization, with a water contact angle of 152°. When the initial dispersion location of the modified diatomite particles changed from water to oil, a hydrophilic/underwater superoleophilic surface with micro/nanoscale hierarchical structures formed on the polymer microspheres. This special wettability enabled the microsphere layer to serve as an adsorbent with underwater superoleophilicity, achieving efficient oil separation from various oil-in-water emulsions with high separation efficiency of >99.8%. Hence, this study provides a valuable strategy based on the Pickering emulsion template method to design materials with special wettability for realizing promising emulsion separation.

Stable water-in-oil (W/O) emulsions can produce at many industrial production occasions. However, most materials for its separation have serious fouling problems. To overcome this shortcoming, we fabricated an easy cleaning multifunctional starch-based material with unique wetting behavior which could realize efficient separation and purification of W/O emulsions. This material has a hierarchical structure and superoleophilic and under oil superhydrophobic surfaces which could separate various W/O emulsions in a high separation efficiency and flux without external pressure. In addition, the decrease of separation flux was not observed for this material, which can be reused more than 10 times after washing with ethanol and drying after each separation cycle. Furthermore, this material also could realize efficient removal of dyes and heavy-metal and rare-earth ions simultaneously during a separation process. The material shows great potential for separating and purifying stable W/O emulsions produced during the industrial production.

Cationic hyperbranched oligomer poly(N-acryloyl-1,2-diaminoethane hydrochloride) (HADE) was firstly synthesized by Michael addition reaction. And then, a series of cationic flocculants poly(acrylamide/N-acryloyl-1,2-diaminoethane hydrochlorides) (PAM-HADEs) with hyperbranched structure was prepared from HADE as macro-monomer and acrylamide (AM). The structures of PAM-HADEs were characterized by Fourier transform infrared spectrometry, 1H and 13C nuclear magnetic resonance spectroscopy, gel permeation chromatography (GPC) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF). And the properties were systematically evaluated by intrinsic viscosity, zeta potential and hydrodynamic radius. The mechanism of the cationic hyperbranched copolymer used in water treatment was extensively studied via a jar test in which the transmittance of the supernatant, settling time, and average floc size were used to evaluate the flocculability. Compared with the linear flocculant poly (acrylamide/liner-N-acryloyl-1,2-diaminoethane hydrochloride) (PAM-LADE), the novel hyperbranched polymeric flocculants exhibited outstanding flocculability which were reflected by shorter settlement time, high transmittance and large floc size. The primary cause that PAM-HADEs owned excellent flocculability is the more stretching configuration and less chains entanglement of PAM-HADEs in waste-water due to their hyperbranched structure compared with that of the linear PAM-LADE which exhibited curly coil configuration. On the other hand, abundant and exposed cationic terminal groups of PAM-HADEs originated from their hyperbranched structure also hint higher flocculation capacity. At optimum dosages of the polymer, the transmittance of the supernatant is less at low and high pH values, indicating that the natural pH (pH 7.29) of the suspension is the most appropriate pH for the flocculation.

In this article, a fast and high efficient healing hydroxypropyl guar gum (HPG)/poly(N,N-dimethyl acrylamide) (PDMA) hydrogel is prepared by a facile synthesis method. HPG networks are formed through hydrogen-bond interaction between the hydroxyl groups in the HPG chains, and PDMA networks are self-crosslinked without any chemical crosslinker. The cut hydrogel could heal when nanosilica solution is chosen as the connector that is related to the adsorption of polymer to the surface of nanosilica. The fracture stress of the HPG/PDMA gels presents a fast and almost full recovery within a short time (1 min), while the recovery of fracture strain and elastic modulus is related to time in 2 h. The healing efficiency of HPG/PDMA gel is investigated as a function of healing time, HPG content, and N,N-dimethyl acrylamide content. The microscopic healing process and healing mechanism are also discussed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

A series of chemically cross-linked microgel composite hydrogels (MCH gels) with excellent toughness and stretchability were prepared using core–shell polymer microspheres as cross-linking junctions. In our strategy, MCH gels are obtained by connecting microspheres with polyacrylamide (PAAm) chains chemically grafted onto their surfaces, where an organic cross-linking agent is completely unnecessary. The mechanical behavior of the MCH gels was analyzed, and superresolution fluorescence microscopy and scanning electron microscopy were used to investigate their toughening mechanism. The results indicated that the homogeneous network structure resulting from the good compatibility between the core–shell microspheres and matrix was an important reason for the excellent toughness of the MCH gels. In addition to interactions among H bonds in the grafted PAAm chains, reversible deformation of the core–shell microspheres acting as cross-linking junctions, which arises from the flexibility of the microspheres, and the effect of cavitation between the microspheres and matrix could also effectively dissipate energy during deformation of the MCH gels.

The biodegradable polysaccharide hydrogels have attracted much attention due to its biocompatible and non-toxicity. Herein, we report a starch hydrogel synthesized via thiol-ene click reaction between thiol starch (St-SH) and allyl starch (AS). The swelling behaviors, rheological experiment and biodegradable properties of the obtained hydrogel were investigated in details. The chemical structure of functioned starch was confirmed by 1 H-NMR and 13 C-NMR. Moreover, the rheological experiment indicated that starch hydrogel possessed high mechanical strength, and its modulus could be manipulated by the thiol-ene molar ratio. Biodegradation tests revealed that the hydrogel could be biodegradable rapidly in the presence of α-amylase. The biodegradation rate could be controlled by the thiol-ene molar ratio or the concentration of α-amylase. Degradation kinetics from the hydrogel suggested that the degradation/erosion of starch hydrogel come from a combination of both the surface erosion and diffusion mechanisms.

To overcome the adverse effects of salt on the mechanical properties of hydrogels, a facile double cross-linking method has been proposed to synthesize salt-enhanced tough hydrogels. Herein, a poly(hexafluorobutyl methacrylate-acrylamide) hydrogel [P(AAm-co-HFBMA) hydrogel] is prepared by the copolymerization of acrylamide (AAm) and hexafluorobutyl methacrylate (HFBMA) with N,N'-methylene bisacrylamide (NMBA) as a cross-linking agent in a dimethylformamide (DMF)/aqueous solution; DMF is then replaced by water. The results indicate that the tensile fracture stress of the P(AAm-co-HFBMA) hydrogel (20 mol% HFBMA) is as high as 0.43 MPa, which is far better than that of the PAAm hydrogel (ca. 30 kPa). Additionally, with a further increase in the hydrophobic structural units (25 mol% HFBMA), the tensile fracture stress of the P(AAm-co-HFBMA) hydrogel can be increased up to 2.34 MPa. The mechanical strength of the P(AAm-co-HFBMA) hydrogel is significantly enhanced to 3.50 MPa (2 M) from 2.34 MPa (0 M) after it is soaked in aqueous NaCl solutions with various salt concentrations. The mechanical properties and the results of the DSC analysis indicate that the main reason for its mechanical strength to exhibit a unique salt-enhancement trend can be explained as follows. After the P(AAm-co-HFBMA) hydrogel is soaked in the salt solution, the network gradually collapses with the penetration of the small molecules of salt. Thus, the hydrophobic C-F units easily form dynamic cross-linking junctions due to the switchable hydrophobic interaction between C-F groups, which can endow the P(AAm-co-HFBMA) hydrogel with a more effective dynamic energy dissipation mechanism in salt solution.

We study biosourced core-shell particles with a starch-based core and thermo-responsive polymer brush shell using surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) as a Pickering stabilizer. The shell endows the Pickering stabilizer with reversible emulsification/demulsification of oil and water properties. The initiator attached to the starch-based nanosphere (Br-SNP) core particle was first fabricated using the precipitation method. Subsequently, dense poly( N-isopropylacrylamide) (PNIPAM) brush graft-modified starch-based nanoparticles (SNP- g-PNIPAM) were obtained via the SI-SET-LRP process. Interfacial properties of the resultant particles were analyzed by interfacial tensiometer measurements, as were the effects of the grafted polymer chain length and temperature on the interfacial activity. Pickering emulsion was obtained using SNP- g-PNIPAM particles as the stabilizer. The effect of the concentration of the Pickering stabilizer on the size of emulsion droplets was analyzed. The emulsification/demulsification process of the Pickering emulsion can be reversed and easily repeated by changing the temperature.

We developed tough, rapid-recovery composite hydrogels that are fabricated via core–shell microgel covalent bonding and Fe3+ dynamic metal coordination cross-linking. First, core–shell microgels are used as cross-linking agents and initiators to prepare homogeneous hydrogel networks with rapid recovery in the absence of an organic cross-linking agent. The toughness and recoverability of the composite hydrogels can be improved by adding the dynamic reversibility of ionic cross-linking. Owing to the synergistic effect of microgel covalent bonding, Fe3+ coordination cross-linking, and H-bond cross-linking, the multi-cross-linked composite hydrogels exhibit excellent toughness and a fast recovery rate. These characteristics demonstrate that the dynamic reversibility of the ionic cross-linking can significantly improve the toughness and recoverability of the hydrogels. In addition, the core–shell microgels play a key role in toughening the hydrogels and accelerating their recovery by transferring stress to grafted polymer chains and homogenizing the hydrogel network.

The convenient synthesis of core-shell nanoparticles containing degradable components is very desirable given the potential applications of such nanoparticles in biomaterials. A facile approach for producing monodisperse starch-polystyrene nanocomposites with well-defined core-shell structures in the absence of a surfactant was developed. The initially-formed Pickering emulsions underwent conversion into seeded emulsions during the polymerization, wherein the amphiphilic starch-based nanospheres (SNPs) serve as stabilizer and seed. A possible mechanism for this transition was explored based on the morphology and size variations of the emulsion droplets and the resultant nanospheres. The effects of the monomer concentration, SNP content and size, and pH on the core-shell nanospheres were investigated. With increasing monomer concentration, the core size of the particles remained almost unchanged, while the shell layer thickness increased almost linearly. The size of the core-shell nanospheres can be regulated by adjusting the pH and the SNP content and size.

Using a facile two-step method, the researchers synthesized a pH-responsive double-network (DN) hydrogel with high strength and toughness, consisting of a B(OH)4− linked hydroxypropyl guar gum (HPG) network and a covalently cross-linked polyacrylamide (PAAm) network. The mechanical strength of HPG/PAAm DN gel was investigated as a function of synthesis conditions, HPG content, sodium borate concentration and soaking time. The resulting DN gel exhibited unique pH-responsive properties and excellent mechanical properties, with a fracture stress of 843 kPa, and an excellent extensibility of 1400% (12−14 times its initial length). The relationship between mechanical property and the synergy of HPG and PAAm networks was discussed systematically. The DN gel possessed self-recovery under small deformation, but displayed self-reinforcement under large deformation.

Although lots of impact protective materials reported exhibited better impact protective performance thanking to their excellent mechanical performance, their applications were still seriously impeded due to absence of soft–stiffness switch smartness. Herein, a novel impact hardening polymer (IHP) with negative Poisson's ratio was synthesized via a condensation polymerization, followed by a simple thermal annealing to achieve a perfect soft–stiffness switch characteristic and self-healing capacity. Its soft–stiffness switch ability σ , defined as G ′ max / G ′ min in rheological analysis, can reach 9000, which is never reported so far. The result of laser speckle scatter measurement elucidates that IHP has negative Poisson's ratio, which is the root cause why IHP exhibits soft–stiffness switch capacity. Finally, 3D composite anti-impact fabrics were prepared by dip–coating IHP dispersion onto a 3D porous polyester fabric. Not only the impact protective performance of anti-impact fabrics finished with the IHP is significantly improved, but also the flexibility and hand feeling of anti-impact fabrics finished with the IHP are obviously very good because the IHP is flexible without impact.

In this study, multi-sensitive hydrogels with high mechanical strength were successfully prepared by in situ free-radical polymerization of acrylamide, acrylic acid and acryloyloxyethyl trimethyl ammonium chloride monomers in the presence of microgels in aqueous media. Microgels with amine groups on the surface were used as polyfunctional initiating and cross-linking centers to fabricate a network. The microgel-based hydrogels synthesized did not fracture upon loading up to 30 MPa and a strain above 99 % when the water content was about 84 wt%. As for the swelling behaviors of the microgel-based hydrogels, they were susceptible to pH and salt concentration. Meanwhile, deswelling tests indicated that the microgel-based hydrogels had thermo-sensitive properties and under high temperature exhibited a faster shrinking rate, which could be attributed to the solvent channels caused by the shrinkage of microgels due to their thermo-sensitive core. And microgel-based hydrogels with various deswelling rates can be determined by regulating the content and species of microgel. Furthermore, the low extensibility of microgel-based polyampholyte hydrogels could be improved by creating a hybrid network with microgels and a small amount of N,N’-methylenebisacrylamide served as the chemical cross-linkers. The hybrid hydrogels possessed superior compressive strength and simultaneously showed abnormal elongation of up to 1000 %.

Series of anionic flocculants with outstanding flocculation performance, poly(acrylic acid-co-acrylamide)/diatomite composite flocculants (PAAD) were successfully prepared through aqueous solution copolymerization and applied to flocculate from oil-field fracturing waste-water. The structure of PAAD was characterized by Fourier transform infra-red spectroscopy , 13C nuclear magnetic resonance and X-ray diffraction tests, and its properties were systematically evaluated by viscometer, thermogravimetry analysis and flocculation measurements. Furthermore, the influences of various reaction parameters on the apparent viscosity of flocculant solution were studied, and the optimum synthesis condition was determined. The novel composite flocculants exhibited outstanding flocculation properties. Specifically, the dosage of composite flocculants that could make the transmittance of treated wastewater exceed 90% was only approximately 12–35 ppm, which was far lower than that of conventional flocculants. Meanwhile, the settling time was lower than 5 s, which was similar to that of conventional flocculants. This was because PAAD flocculants had a higher absorption capacity, and larger chain extending space than conventional linear flocculants, which could refrain from the entanglement of linear polymer chains and significantly improve flocculation capacity.

An in situ hydrogel based on oxidation cholesterol starch (OCS) and O-carboxymethyl chitosan (CMCT) that is completely devoid of potentially cytotoxic small molecule cross-linkers and does not require complex manoeuvres or catalysis has been formulated and characterized. The network structure was created by Schiff base formation. The mechanical properties, internal morphology and swelling ability of the injectable hydrogel were examined. Rheological measurements demonstrated that increasing the concentration of the monomer improved the storage modulus. SEM showed that the hydrogel possessed a well-defined porous structure. In addition, the Schiff base reaction was acid sensitive. Under acid conditions, the hydrogel could hydrolyse quickly compared with high pH conditions. Doxorubicin (DOX) was used as a model drug to investigate the control and release properties of the hydrogel. The cytotoxic potential of the hydrogel was determined using an in vitro viability assay with L929 cells as a model and the results revealed that the hydrogel was non-cytotoxic.

Understanding the interfacial activity of polysaccharide nanoparticles adsorbed at oil–water interfaces is essential and important for the application of these nanoparticles as Pickering stabilizers. The interfacial properties of starch-based nanospheres (SNPs) at the interface of an n-hexane–water system were investigated by monitoring the interfacial tension at different bulk concentrations. The three-phase contact angle (θ) and the adsorption energy (ΔE) increased with increasing size and degree of substitution with octenyl succinic groups (OSA) in the particles. Compared with the OSA-modified starch (OSA-S) macromolecule, the SNPs effectively reduced the interfacial tension of the n-hexane–water system at a relatively higher concentration. These results and the method reported herein are useful for selecting and preparing polysaccharide nanoparticles as Pickering stabilizers for oil–water emulsions.

We developed tough, rapid-recovery composite hydrogels that are fabricated via core-shell microgel covalent bonding and Fe

Conventional approaches to generating double emulsions are cumbersome, complicated, and based on a two-step emulsification process using a combination of two distinctive surfactants. In this work, the surface properties of diatomite particles were successfully tailored by chemical modification with palmitoyl chloride. The properties of the resulting diatomite particles changed from the original hydrophilicity to hydrophobicity, leading to straightforward stabilization of oil-in-water-in-oil (O/W/O) Pickering double emulsions by a one-step emulsification process. Pickering double high internal phase emulsions (HIPEs) with an internal phase up to 80 vol% could be produced solely using the modified diatomite particles. The water-in-oil (W/O) droplet sizes of these HIPEs were much larger than the droplets of conventional nanoparticle-stabilized Pickering HIPEs. Furthermore, using the O/W/O Pickering double emulsions as templates, the porous polymer particles were fabricated. In addition, it was demonstrated that the wide particle size distribution of diatomite particles and modified heterogeneity were the reasons for the formation of multiple emulsions.

Conventional hydrogels freeze and harden at sub-zero temperatures and their mechanical properties are considerably inadequate for practical load-bearing applications. These drawbacks hinder their application possibilities. In this work, we propose a new strategy based on Pickering emulsion polymerization to fabricate novel organohydrogels with antifreeze properties. Ethylene glycol (EG) is introduced into the aqueous phase of the Pickering high internal phase emulsion (HIPE) to effectively inhibit water from freezing. The resulting bicontinuous organohydrogels are prepared through simultaneous polymerization in the external and internal phases to provide enhanced mechanical properties and good hydrophilic-oleophilic properties. Furthermore, the organohydrogels are more stable than conventional hydrogels under ambient conditions and remain unfrozen and mechanically flexible down to −40 °C.

A tetranuclear neutral MRI contrast agent, (Gd-DO3A)4-TPM, was designed and synthesized by appending four Gd-DO3A moieties upon the tetraphenylmethane derivatives. The longitudinal relaxivity of (Gd-DO3A)4-TPM measured at 20 MHz, 37 °C and pH 7.0 is 6.8 mM–1·s–1 per Gd atom, which is one-fold higher than that of the mononuclear clinical agent [Gd(DOTA)(H2O)]–. In addition, the thermodynamic stability of (Gd-DO3A)4-TPM was higher than that of [Gd(DTPA)(H2O)]2–. The luminescence lifetime study on the (Eu-DO3A)4-TPM analogue suggested that the complex contains one inner water molecule coordinated to each Ln3+ ion. The cytotoxicity study of (Gd-DO3A)4-TPM indicated quite low toxicity.

A series of amphoteric hydrophobic-associative flocculants with outstanding flocculation efficiency and salt tolerance, poly(acrylamide/acrylic acid/dimethyl benzyl aminoethyl acrylate chloride), are successfully prepared (named AAB series) and used to flocculate the montmorillonite suspensions. The solution properties of AAB copolymer are systematically evaluated by viscometer, rheology and steady-state fluorescence analysis. The results suggest that the space network structure forming via hydrophobic-associating interaction can increase solution viscosity and improve the bridging capacity of copolymers. Meanwhile, the apparent viscosity in salt solution increases with increase in the concentration of salt stemming from the anti-polyelectrolyte effect of polyampholyte. Further, the flocculation performances of flocculants in 1 wt% montmorillonite suspensions are evaluated by turbidity, optimal dosage and settlement rate measurement. The results elaborate that the flocculation performances of amphoteric hydrophobic-associating AAB flocculants are better than that of commercial flocculants (cationic and anionic polyacrylamide) and homemade cationic flocculant (AAB-0-5) independent of the type and concentration of salt. The novel ampholyteric hydrophobic-associative flocculants will exhibit intriguing prospective in industry water treatment, in that the anti-polyelectrolyte effect of polyampholyte and hydrophobic-associating interaction can endow excellent flocculation efficiency and salt tolerance.

Polysaccharide-based hydrogels are remarkable materials for the biomedical fields because of its excellent biodegradation and biocompatibility. In this work, a novel polysaccharide-based hydrogel was fabricated by in situ crosslinking of starch-based nanoparticles and polyvinylamine. Starch was decorated with cholesterol group and aldehyde groups. TEM and DLS showed that the cholesterol modified oxidation starch (OCS) exhibited a core-shell nanoparticles with mean size of ∼143 nm in aqueous. The hydrogel was then synthesized via Schiff base reaction. Rheological measurements demonstrated the incorporation of cholesterol groups not only reduced the gel time but also improved the storage modulus of the hydrogel compared with the oxide starch crosslinked hydrogel. SEM showed the OCS based hydrogels possess a well-defined porous structure. Furthermore, doxorubicin (DOX) was used as model drug to investigate the control and release properties of OCS hydrogels. This OCS hydrogel would be a promising drug carrier for biomedical applications.

Emulsions stabilized solely by edible particles have attracted great interest very recently because of their potential application in the food and pharmaceutical fields. In this work, starch-based nanospheres are used as the particulate emulsifier for triglyceride–water emulsions. The effects of particle concentration, oil:water ratio and salt concentration on emulsion type and stability are investigated in detail. The linear relationship between the inverse average oil drop diameter and the particle concentration allows estimation of the coverage by particles of the curved oil–water interfaces. Confocal microscopy confirms that the nanospheres are mainly adsorbed at the liquid interface to form a dense film around the dispersed drops impeding coalescence. Moreover, catastrophic phase inversion from oil-in-water (O/W) to water-in-oil (W/O) emulsions is achieved by increasing the volume fraction of oil beyond 0.65. The stability to creaming of O/W emulsions increases approaching phase inversion, as does the stability to sedimentation of W/O emulsions. Finally, O/W emulsions are destabilized with respect to coalescence on adding salt.

Biodegradable thermosensitive hydrogels have attracted great interest because of their potential in biomedical applications. Herein, we present a novel, thermoresponsive poly(2-(2-methoxyethoxy)ethyl methacrylate) hydrogels with starch-based nanospheres as cross-linkers (NMH). NMHs exhibit a narrow lower critical phase transition temperature (LCST) range and high mechanical strength compared with conventional, small molecular cross-linked hydrogels (CMH). Fourier transform infrared (FT-IR) spectroscopy confirms that the NMHs are degradable in aqueous medium. The phase transition temperature of the NMHs is ∼4 °C compared with ∼25 °C for CMH. The NMHs can sustain strength of 12.2 MPa, 10 times more than that of CMH. Moreover, the deswelling rate of NMHs is faster than CMH. The different concentrations of nanospheres can efficiently regulate the various properties of NMHs. The NMHs have excellent properties because of its even network structure formed by nanosphere cross-linkers.

Fundamental understanding of the fracture process and toughening mechanisms of double network (DN) hydrogels is critical for rational design of the next generation of tough DN gels with desirable mechanical properties. However, current knowledge of DN gels from synthesis methods to toughening mechanisms mainly comes from chemically cross-linked DN gels. Little is known about hybrid physically chemically cross-linked DN gels. Herein, we synthesize tough DN hydrogels by combining two types of cross-linked polymer networks: a physically cross-linked first network of agar and a covalently cross-linked second network of polyacrylamide (PAM). The resulting Agar/PAM DN gels achieved high toughness of 500–1000 J/m2. More importantly, we reveal several differences and similarities between hybrid Agar/PAM DN gels and chemically linked PAMPS/PAM DN gels. First, different from the nearly velocity-independent mechanical properties in chemically linked DN gels, hybrid Agar/PAM DN gels show velocity-dependent fracture b...

1H spin-spin relaxation time(T 2) measurement of polyampholyte hydrogel poly(methylacrylic acidacryloyloxyethyl trimethylammonium chloride)[P(MA-DAC)] in different pH, ionic strength and temperature was carried out to reveal the molecular mobility. Spontaneous volume transition of the polyampholyte hydrogel was also investigated by spin-spin relaxation time measurement. Meanwhile T 2 and the proton component fraction were acquired to study the swelling behaviour of the hydrogel. Moreover the changes of T 2 characterized the molecular mobility of polyampholyte hydrogel in various swelling states. And the results suggest that the mobility of the main chains and a few free side chains(the long T 2) of P(MA-DAC) was dominated by the mesh size in the hydrogel network, depending on the swelling ratio(Q) and the mobility of the side chains(the short T 2) was influenced by electrostatic interaction between different charges in polymer side chains. Finally the T 2 measurements of P(MA-DAC) hydrogel in the spontaneous swelling-deswelling process demonstrated the electrostatic interaction of the charged side chains caused deswelling behavior. At the same time, the mobility state transition temperature of the charged side chains was also studied by the 1H spin-spin relaxation time measurements, and the transition activation energy of the side chains is 2.72 kJ.

High strength, stimuli-responsive poly(acrylamide) composite hydrogels (PAAm CH gels) were prepared by grafting polymerization of acrylamide (AAm) onto temperature-sensitive core–shell microgels. These microgels, composing of poly(N-isopropylacrylamide) as core and polyvinylamine (PVAm) as shell, were used as both initiator and crosslinker to form a robust three-dimensional network via bonding the poly(acrylamide) (PAAm) backbone. The CH gels exhibited a remarkably rapid shrinking rate and transmittance switch in response to the environmental temperature change, which the conventional chemically cross-linking PAAm hydrogels (PAAm OR) were short of. Even compared to the bulk PNIPAAm hydrogels (PNIPAAm OR) crosslinked with N,N′-methylenebisacrylamide (MBA), the CH gels were featured with faster responsive rate, which could be attributed to the formation of interconnected water transportation channels between the microspheres and PAAm gel matrix due to the fast shrinking of microgels. Moreover, the effects of microgel species and content on swelling and mechanical properties of CH gels were also systematically investigated. The results elaborated that the CH gels could be compressed almost 99% without breaking and completely recovered their original shape when the stress was removed. And the optimized compressive strength of CH gels could be up to 21.94 MPa. Based on the analysis of CH gel mechanical properties, the influence of microsphere content on effective network chains density of CH gels was discussed through rheology measurements. Finally, the essential reinforcement on mechanical properties was mainly contributed to the homogeneous microstructure of hydrogel network and the energy dissipation mechanism of microgels in gel matrix.

A cationic surfactant monomer, dimethyldodecy1(2-acrylamidoethypammonium bromide (AMQC(12)) was synthesized. A family of hydrophobic-associating cross-linking hydrogels (HAC-gels) fabricated via the self-assembly of amphiphilic multiblock copolymers of acrylamide and AMQC-12 can be synthesized by free-radical aqueous solution micelle copolymerization in the absence of surfactants using the one-pot method. The HAC-gels possessed outstanding mechanical performance, with optimal tensile strength, compressive strength, and elongation at break of 250 kPa, 14 MPa, and 1850%, respectively. Meanwhile, the HAC-gels exhibited self-healing property, and tetrahydrofuran (THF) significantly accelerated their self-healing process. The recovery hysteresis of hydrophobic-associating hydrogels prepared in the presence of surfactants can be eliminated because of homogeneity of the hydrogel network and the dynamic and mobile properties of physical cross-linking junctions. Investigations on the mechanical property and structure evolution of hydrogels revealed that the hydrophobic-associating interaction was the driving force of self-assembly of amphiphilic multiblock copolymers. Furthermore, spherical micelles and macroscopic cross-linking network can be easily switched reversibly by regulating copolymers concentration. (C) 2013 Elsevier Ltd. All rights reserved.

Two macrocyclic chelating MRI agents (Gd-DO3A)(3)-TAB and (Gd-DO3A)(2)-DAB have been successfully synthesized by appending three and two Gd-DO3A moieties upon the acetylbenzene derivatives, respectively. The longitudinal relaxivity of (Gd-DO3A)(3)-TAB measured at 20 MHz, 37 degrees C and pH 7.0 is 6.1 mMGd(-1) s(-1), 74% higher than that of the mononuclear clinical agent [Gd(DOTA)(H2O)]. A 30% or 16% increase in relaxivity was observed upon addition of 0.72 mMbovine serum albumin (BSA) or 10-fold of diamagnetic ion La3+. More importantly, the thermodynamic stability and kinetic inertness of (GdDO3A)(3)-TAB are comparable to or better than that of [Gd(DTPA)(H2O)](2). The luminescence lifetime study on the corresponding (Eu-DO3A)3-TAB analog demonstrated that the agent had one inner-sphere water coordinated to the Eu3+ center within the complex. The cytotoxicity study indicated that the toxicity of the agent was low with IC50 = 18 mM. In addition, the characterization of its dinuclear analog (GdDO3A)(2)-DAB has also been investigated. (C) 2013 Elsevier B.V. All rights reserved.

A novel kind of impact protective material, named as impact protective micro-gel (IPM), was synthesized via a precipitation copolymerization of a compound containing boron and silanol. Diphenylmethane diisocyanate (MDI) was introduced as the chain extender to enhance its impact protective performance. Its rheological properties and morphology were investigated. Three-dimensional (3D) spacer warp-knitted fabrics were dip-coated with the IPM made with and without use of MDI, and the impact protective performance of 3D finished fabrics was assessed by drop impact tests. The results show that the adjustment of the MDI content can adjust the real cross-linking density of the IPM due to the entanglement of polymer chains, and an appropriate cross-linking density can endow dilatant properties to the IPM samples. The results also show that the impact protective performance of 3D spacer fabrics finished with the IPM can be significantly improved. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2345-2351, 2013

Starch is successively modified by acetic anhydride and phthalic anhydride, and then starch-based nanospheres are fabricated by a simple nanoprecipitation procedure. These pH-responsive amphiphilic starch-based nanospheres of uniform size are used as particulate emulsifiers to stabilize Pickering emulsions. CLSM and SEM characterization find that starch-based nanospheres adsorbed at the interface between oil phase and water phase. Moreover, the catastrophic inversion and transitional inversion of such emulsions can be easily achieved by varied the water/oil volume ratio and pH of aqueous dispersion, respectively.

Thermoplastic polyurethane (TPU)/organoclay nanocomposites are prepared through a melt extrusion process. The TPU is combined with four differently modified organoclays, namely, I.28E, I.30P, I.34TCN, and I.44P. Wide-angle X-ray diffraction and transmission electron microscopy results show that the addition of I.34TCN and I.30P to TPU/organoclay nanocomposites results in the nearly exfoliated structures of the nanocomposites. Addition of I.28E leads to partially intercalated nanocomposites, whereas I.44P cannot disperse effectively in the nanocomposites. Organoclay can enhance the mechanical and gas barrier properties of TPU. The enhancement follows the order TPU/I.34TCN ≥ TPU/I.30P > TPU/I.28E > TPU/I.44P, which is consistent with the degree of dispersion and exfoliation of silicate layers. In addition, Fourier transform infrared absorption spectra show that more hydrogen bonding sites are introduced between the clay modifiers and TPU chains in the TPU/I.34TCN and TPU/I.30P nanocomposites; this has a positive impact on the dispersion of the organoclay and, consequently, the mechanical and gas barrier properties of the nanocomposites.