Formation mechanism of zigzag patterned P(NIPAM-co-AA)/CuS composite microspheres by in situ biomimetic mineralization for morphology modulation

Poly(N-isopropylacrylamide-co-acrylic acid)/copper sulfide (P(NIPAM-co-AA)/CuS) composite microspheres with variable zigzag patterned surfaces have been synthesized by employing an in situ biomimetic mineralization reaction between H₂S and Cu²⁺ immersed in P(NIPAM-co-AA) microspheres for morphology modulation. The morphology and composition of the P(NIPAM-co-AA)/CuS composite microspheres with zigzag patterned surfaces prepared in different conditions were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FT-IR). The polymeric microgels swelled by Cu(Ac)₂ solution after freeze-drying treatment were of porous structure, indicating that there were polymeric frameworks and rich-water domains in the microgels before the deposition. Furthermore, due to the limited uneven deposition of metal sulfide on the polymeric skeleton of the hydrogel surface, the surface polymeric skeleton will be anisotropically shrunk when the composite microspheres lose water and shrink, thus forming a wrinkle pattern on the surface of the composite microspheres. The factors affecting the deposition amount and distribution of metal sulfide will affect the zigzag patterned morphology. Based on the experimental results, a formation mechanism of the P(NIPAM-co-AA)/CuS composite microspheres with zigzag patterned surface, “the deformed shrinkage of the surface texture”, has been proposed. The formation mechanism of the surface morphology in the composite microspheres is helpful for understanding and controlling the process of mineralization, for preparing materials expected by controlling the experiment conditions, and for expanding the application of the composites.

P(NIPAM-co-AA)/CuS composite microspheres with zigzag patterned surfaces were synthesized, and a mechanism for “the deformed shrinkage of the surface texture” was proposed. The surface morphology is sensitive to factors such as K_sp, pH, temperature, deposition amount, etc.     

Fabrication and characterization of silicon oxycarbide fibre-mats via electrospinning for high temperature applications

Electrospinning is an emerging technique for synthesizing micron to submicron-sized polymer fibre supports for applications in energy storage, catalysis, filtration, drug delivery and so on. However, fabrication of electrospun ceramic fibre mats for use as a reinforcement phase in ceramic matrix composites or CMCs for aerospace applications remains largely unexplored. This is mainly due to stringent operating requirements that require a combination of properties such as low mass density, high strength, and ultrahigh temperature resistance. Herein we report fabrication of molecular precursor-derived silicon oxycarbide or SiOC fibre mats via electrospinning and pyrolysis of cyclic polysiloxanes-based precursors at significantly lower weight loadings of organic co-spin agent. Ceramic fibre mats, which were free of wrapping, were prepared by a one-step spinning (in air) and post heat-treatment for crosslinking and pyrolysis (in argon at 800 °C). The pyrolyzed fibre mats were revealed to be amorphous and a few microns in diameter. Four siloxane-based pre-ceramic polymers were used to study the influence of precursor molecular structure on the compositional and morphological differences of cross-linked and pyrolyzed products. Further thermal characterization suggested the potential of electrospun ceramic mats in high temperature applications.

Electrospinning of ceramic mats for high temperature applications.     

Chitosan-g-oligo/polylactide copolymer non-woven fibrous mats containing protein: from solid-state synthesis to electrospinning

Graft-copolymers based on bioresorbable synthetic (oligo-/polylactide) and natural (chitosan and collagen/gelatin) components were synthesized through solid-state reactive co-extrusion and used for fabrication of fibrous non-woven mats via the electrospinning technique. The effect of the macromolecular features of the initial components on the copolymer characteristics was evaluated using FTIR-spectroscopy, differential scanning calorimetry and elemental analysis. Dynamic light scattering analysis showed that the copolymers have a tendency to form stable ultra-fine dispersions with a mean size of macromolecular aggregates of 150 nm within chlorinated solvents. The copolymer-containing non-woven fibrous mats were fabricated via an electrospinning procedure using chloroform as a solvent. An effect of the copolymer composition on the casting solution''s viscosity, conductivity and surface tension was evaluated. Scanning electron microscopy showed that the obtained mats consist of randomly distributed fibers with a mean size of ∼5 μm and a more complex morphology than mats fabricated from neat polylactide. The proposed mechanochemical approach to obtain hybrid copolymeric compositions differs from typical liquid-phase methods in terms of high efficiency, simplicity and cleanness.

Amphiphilic chitosan-g-oligo/polylactide graft-copolymers were synthesized through solid-state reactive co-extrusion and used for fabrication of fibrous non-woven mats via the electrospinning technique using chloroform as a solvent.     

Effect of tourmaline nanoparticles on the anticoagulation and cytotoxicity of poly(l-lactide-co-caprolactone) electrospun fibrous membranes

Tourmaline nanoparticles (TM NPs) were well dispersed in poly(l-lactide-co-caprolactone) (PLCL) fibers via electrospinning without a dispersant. Through the modification of TM NPs, the hydrophilicity and anticoagulant property of the composite electrospun fibrous membranes were improved. Compared with the PLCL membranes, the curve of dynamic clotting time in contact with the composite TM NPs/PLCL membranes descended more slowly. Particularly, the coagulation time of 8 wt% TM NPs/PLCL membrane was longer than 70 min, which was 174% higher than that of the PLCL membrane. At the same time, the cell compatibility and mechanical properties of TM NPs/PLCL membranes were analyzed. The cytotoxicity test showed that the grade of 8 wt% TM NPs/PLCL membrane was 0. The stretching experiments showed that the tensile strength of 8 wt% TM NPs/PLCL membrane (6.71 ± 0.30 MPa) was 267.33% higher than that of the PLCL membrane, and its elongation at break (141.83 ± 5.82%) was higher than the requirement of the coronary artery. These results indicated that the PLCL electrospun fibrous membranes modified with TM NPs have potential to be used in tissue engineering as small-caliber vascular grafts.

The hydrophilicity and anticoagulation of PLCL electrospun membranes were enhanced by the modification of well-dispersed TM NPs.     

Poly(pyrrole-co-o-toluidine) wrapped CoFe2O4/R(GO–OXSWCNTs) ternary composite material for Ga3+ sensing ability

In this study, we report a novel ternary conductive hybrid material with high stability, conductivity, and excellent electrochemical Ga³⁺ sensing ability. Ternary poly(pyrrole-co-o-toluidine)/CoFe₂O₄/reduced graphene oxide–oxidized single-wall carbon nanotube nanocomposites in the form of P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs have been synthesized through an in situ chemical polymerization method via a facile three-step approach. Single phase CoFe₂O₄ (CF) nanoparticles (NPs) were synthesized using an egg white method, while reduced graphene oxide–oxidized single-wall carbon nanotubes R(GO–OXSWCNTs) were prepared via co-reduction of graphene oxide along with oxidized SWCNTs flowed by coating CF and R(GO–OXSWCNTs) with a poly(pyrrole-co-o-toluidine) matrix P(Py-co-OT) copolymer. The results of X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR) and Raman indicated that the P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs were effectively synthesized with strong interactions among the constituents. The thermal stability of P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs is considerably enhanced in the composite format. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) demonstrated that CF and R(GO–OXSWCNTs) were well coated by P(Py-co-OT). The electrical conductivity study showed that P(Py-co-OT) and R(GO–OXSWCNTs) might significantly improve the conductivity and the electrochemical performance of the CF. A Ga³⁺ ion selective electrochemical sensor was fabricated by coating a glassy carbon electrode (GCE) with synthesized P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs by using 5% Nafion binder. The slope of the calibration curve was used to calculate the sensor''s analytical parameters, such as sensitivity (13.0569 μA μM⁻¹ cm⁻²), detection limit (96.27 ± 4.81 pM), quantification limit (43.523 pM), response time, reproducibility, large linear dynamic range, and linearity. The validation of the P(Py-co-OT)/CF/R(GO–OXSWCNTs) NCs/GCE sensor probe was investigated by a standard addition method (recovery) in the presence of various environmental samples and satisfying results were obtained.

A ternary P(Py-co-OT)/CF/R(GO–OXSWCNTs) nanocomposite has been fabricated as a novel conductive hybrid material with high stability and excellent electrochemical Ga³⁺ sensing ability.     

Effect on thermal stability of microstructure and morphology of thermally-modified electrospun fibers of polybenzoxazines (PBz) blended with sulfur copolymers (SDIB)

Simple modification by thermal treatment is the commonly used approach to enhance the performance of electrospun fibers. This was investigated in the thermal treatment of polybenzoxazine (PBz) fibers blended with sulfur copolymers (SDIB) to determine the effect of varying treatment conditions on the microstructure and morphology of PBz fibers with the effect of incorporating sulfur functional groups on resulting properties. Mechanical properties of PBz are greatly improved by thermally-induced ring-opening polymerization (ROP) of the oxazine ring. Blending with sulfur copolymers (SDIB) could have beneficial effects on endowed features on fibers but could also affect the resulting properties of SDIB-blended PBz fibers during crosslinking reactions. Fiber mats were fabricated by electrospinning of PBz (10 wt%) blended with SDIB (10 wt%). Physical modification with varying conditions of sequential thermal treatment were evaluated and compared to the conditions applied on pristine PBz fibers. Changes in morphology and microstructure of fibers after modification were analyzed through scanning electron microscopy (SEM) while elemental compositions were identified after varying the conditions of thermal treatment. Adjustment of treatment conditions using two-step temperature sequential thermal treatment with higher temperatures of 160 °C and 240 °C showed significant changes in microstructure and morphology of fibers. Lower temperatures of 120 °C and 160 °C exhibited microstructure and morphology of fibers which affected the fiber diameter and fiber networks. Cross-sectional SEM images also confirmed the adversed effect of high-temperature treatment conditions on fibrous structures while low-temperature treatment retained the fibrous structures with more compact and stiff fiber networks. SDIB-blended PBz fibers were also evaluated by TGA and DSC to correlate the changes in structure and morphology with the thermal stability and integrity of blended SDIB/PBz fibers as compared to pristine PBz with the effect of change in treatment conditions. Fiber strength indicated slower weight loss for blended fibers and higher onset temperature of degradation which resulted in more thermally stable fibers.

Microstucture and morphology of thermally-modified electrospun fiber of PBz blended with SDIB that enhanced structural satbility and integrity.     

Thermosensitive star polymer pompons with a core–arm structure as thermo-responsive controlled release drug carriers

In contrast with traditional chemotherapy, controlled drug delivery systems provide many advantages. Herein, a thermosensitive star polymer pompon with a core–arm structure was synthesized using a grafting-on method as a thermo-responsive controlled release drug carrier. Single-chain cyclized/knotted poly tetra(ethylene glycol) diacrylate (polyTEGDA) was used as the hydrophobic core, and thermosensitive linear poly(N-isopropylacrylamide-co-N-methylolacrylamide) (poly(NIPAM-co-NMA)) was selected as the hydrophilic arm. Below or above its lower critical solution temperature (LCST), the linear poly(NIPAM-co-NMA) grafted onto the polyTEGDA core adopted a stretched or curled status, respectively, then the drug could be loaded in or extruded out. The LCST of star polyTEGDA-b-poly(NIPAM-co-NMA) was adjusted to slightly above body temperature (37 °C). The antitumor drug doxorubicin (DOX) was successfully loaded into the pompons with a high loading capacity of 19.45%. The cumulative release of DOX from loaded pompons in vitro for 72 hours was 71% and 20.7% at 42 °C and 37 °C, respectively, indicating that the excellent temperature-controlled release characteristics result from the unique thermo-responsive extrusion effect. Moreover, DOX loaded polyTEGDA-b-poly(NIPAM-co-NMA) pompons achieved better antitumor ability against ovarian carcinoma SKOV3 cells at 42 °C compared with that at 37 °C. These results suggest that star polyTEGDA-b-poly(NIPAM-co-NMA) pompons have considerable promise as thermo-responsive controlled drug delivery carriers.

Herein, a thermosensitive star polymer pompon with a core–arm structure was synthesized using a grafting-on method as a thermo-responsive controlled release drug carrier.     

Crosslinked poly(methyl methacrylate) with perfluorocyclobutyl aryl ether moiety as crosslinking unit: thermally stable polymer with high glass transition temperature

Crosslinked poly(methyl methacrylate) (PMMA) with high glass transition temperature (T_g) and thermal decomposition temperature was prepared by simple thermal crosslinking of PMMA-containing random copolymers bearing aryl trifluorovinyl ether (TFVE) moieties. A methacrylate monomer consisting of aryl TFVE moiety, 4-((1,2,2-trifluorovinyl)oxy)phenyl methacrylate (TFVOPMA), was first synthesized followed by radical copolymerization with methyl methacrylate (MMA) initiated by AIBN, providing the random copolymer containing aryl TFVE moieties, poly(4-((1,2,2-trifluorovinyl)oxy)phenyl methacrylate)-co-poly(methyl methacrylate) (PTFVOPMA-co-PMMA). Finally, crosslinked PMMA polymer with perfluorocyclobutyl (PFCB) aryl ether moieties as crosslinking units was obtained by [2π + 2π] cycloaddition reaction of aryl TFVE moieties in PTFVOPMA-co-PMMA copolymer. Thermal properties of both PTFVOPMA-co-PMMA and crosslinked PTFVOPMA-co-PMMA were examined by TGA and DSC. Compared to pure PMMA, T_g of PTFVOPMA-co-PMMA increased by 15.1 °C and no T_g was found in the DCS test of the crosslinked PTFVOPMA-co-PMMA. Thermal decomposition temperature (T_d,5%) of crosslinked PMMA was 47 °C higher than that of pure PMMA. Furthermore, the water absorption of crosslinked PMMA film greatly reduced in comparison with that of pure PMMA.

PMMA-based copolymer containing aryl TFVE moieties prepared by copolymerization of MMA and TFVOPMA monomer containing aryl TFVE group and thermal cross-linked by [2π + 2π] cycloaddition reaction of aryl TFVE moieties.     

Fibrous biodegradable l‐alanine‐based scaffolds for vascular tissue engineering

In vascular tissue engineering, three‐dimensional (3D) biodegradable scaffolds play an important role in guiding seeded cells to produce matrix components by providing both mechanical and biological cues. The objective of this work was to fabricate fibrous biodegradable scaffolds from novel poly(ester amide)s (PEAs) derived from l ‐alanine by electrospinning, and to study the degradation profiles and its suitability for vascular tissue‐engineering applications. In view of this, l ‐alanine‐derived PEAs (dissolved in chloroform) were electrospun together with 18–30% w/w polycaprolactone (PCL) to improve spinnability. A minimum of 18% was required to effectively electrospin the solution while the upper value was set in order to limit the influence of PCL on the electrospun PEA fibres. Electrospun fibre mats with average fibre diameters of ~0.4 µm were obtained. Both fibre diameter and porosity increased with increasing PEA content and solution concentration. The degradation of a PEA fibre mat over a period of 28 days indicated that mass loss kinetics was linear, and no change in molecular weight was found, suggesting a surface erosion mechanism. Human coronary artery smooth muscle cells (HCASMCs) cultured for 7 days on the fibre mats showed significantly higher viability (p < 0.0001), suggesting that PEA scaffolds provided a better microenvironment for seeded cells compared with control PCL fibre mats of similar fibre diameter and porosity. Furthermore, elastin expression on the PEA fibre mats was significantly higher than the pure PEA discs and pure PCL fibre mat controls (p < 0.0001). These novel biodegradable PEA fibrous scaffolds could be strong candidates for vascular tissue‐engineering applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation of thermo-responsive drug-loaded nanofibrous films created by electrospinning

We prepared thermosensitive and biocompatible drug-loaded nanofibrous films by an electrospinning technique using a block copolymer, poly(N-isopropylacrylamide)-b-poly(l-lactide) (PNLA), and poly(l-lactide) (PLLA). The copolymer PNLA was synthesized by the radical polymerization of N-isopropylacrylamide (NIPAAm), followed by the ring-opening polymerization of l-lactide. The properties of PNIPAAm and PNLA were selectively discussed based on the results of NMR, FT-IR, GPC, and CA analyses. Because of the low molecular weight of PNIPAAm and PNLA and the hydrolysis of PNLA resulting from its hydrophilicity, these copolymers were inappropriate for electrospinning separately. Hence, a mixture of PNLA and PLLA was used to prepare electrospun nanofibrous films. SEM images of the PNLA/PLLA electrospun films showed that homogeneous fibres with smooth surfaces were obtained. In vitro release studies indicated that the drug-release rate of the PNLA/PLLA electrospun nanofibrous films can be adjusted by the content and molecular weight of PNLA and by the environmental temperature. The results demonstrate that electrospinning is a promising way to create stimuli-responsive fibrous films with potential applications in the design of controllable drug delivery systems.

Thermosensitive and biocompatible PNLA/PLLA drug-loaded nanofibrous films with different morphologies and controlled drug release behaviors by electrospinning technique.     

Silver nanoparticle-loaded microgel-based etalons for H2O2 sensing

Silver nanoparticles (AgNPs) were generated inside the network structure of poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgels that were sandwiched between two thin Au layers (15 nm) of an etalon. This was done by introducing Ag⁺ to the etalons composed of deprotonated microgels, followed by its subsequent reduction with NaBH₄. The resultant microgels were collected and then characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), verifying the loading of AgNPs with relatively uniform diameter (5–7 nm) within the microgels. Furthermore, the optical properties of the resultant etalons and their response to H₂O₂ were evaluated by reflectance spectroscopy. Specifically, upon the addition of H₂O₂, the AgNP-loaded etalons exhibited both a red shift in the position of the reflectance peaks and an increase in reflected wavelength intensity. We hypothesize that the dual signal response of the devices was a result of oxidative decomposition of the AgNPs, enabling the microgels to swell and for more light to be reflected (due to the loss of the light absorbing AgNPs). Finally, we showed that the AgNPs could be regenerated in the used etalons multiple times without a loss in performance. This work provides a cost-effective means to detect H₂O₂, which could be modified to sense a variety of other species of physiological and environmental importance through rationally loading other functional nanomaterials.

Silver nanoparticle (AgNP)-loaded poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc)-based microgels were generated and used to make etalons. The etalons were shown to exhibit optical properties that depended on the concentration of H₂O₂ in solution.     

Enhanced oil removal from water in oil stable emulsions using electrospun nanocomposite fiber mats

Fibrous mats with hydrophobic and oleophilic properties have been fabricated and used as absorbents of oil from stable water in oil emulsions. The mats were prepared by initially mixing two polymers, poly(methyl methacrylate) (PMMA) and polycaprolactone (PCL), in a common solvent. The subsequent electrospinning of the prepared solutions resulted in the production of mechanically stable fiber mats, with enhanced oil absorption capacity and oil absorption selectivity from the emulsions, compared to the pure PMMA or PCL mats. Furthermore, the formed fibrous substrates have been successful in the absorption of oil from different emulsions with a wide range of oil content, from 10 to 80 v%. The performance of the fibrous mats was optimized by the incorporation of hydrophobic silica nanoparticles, reaching oil absorption capacities of 28 g g⁻¹ and negligible water uptake, in the emulsions with 80 v% oil content.

Fibrous mats with hydrophobic and oleophilic properties have been fabricated and used as absorbents of oil from stable water in oil emulsions.     

PBAT/gelatin hybrid nanofibers based on post-double network bond processing as a promising vascular substitute

The development of injured vascular tissue substitutes with proangiogenic, anti-thrombus, and anti-hyperplasia activity still remains a major challenge in vascular tissue engineering. In this study, we have prepared a series of poly(butylene adipate-co-terephthalate)/gelatin hybrid nanofibers (P/G) through random electrospinning and post-double network bond crosslinking for process optimization according to physiochemical and mechanical properties as well as promoting enhanced vascular cell viability in vitro. The gelatin matrix was shown to be successfully contained in the bicomponent hybrid P/G nanofibers, and the formed P/G nanofibers exhibited a uniform and smooth morphology. Importantly, the bicomponent hybrid nanofibers showed a potentially reliable ability to promote the proliferation of human umbilical vein endothelial cells (HUVECs). In addition, all the results demonstrated the significantly stable microstructure, appropriate surface wettability, matched mechanical properties, and excellent blood compatibility, cellular compatibility, and histocompatibility of hybrid nanofibers containing 15 wt% gelation (P/G-15) compared to PG-0, P/G-5, and PG-25 groups, indicating their potential for vascular injury healing.

A PBAT/gelatin hybrid nanofibers vascular graft containing 15 wt% gelation (P/G-15) exhibited matched mechanical properties, especially they demonstrate excellent blood compatibility, cellular compatibility, and histocompatibility in rabbit carotid artery model.     

Electrospinning preparation of a large surface area,hierarchically porous,and interconnected carbon nanofibrous network using polysulfone as a sacrificial polymer for high performance supercapacitors

Carbon nanofibrous mats (CNFMs) are prepared by electrospinning of blended precursor of polyacrylonitrile and polysulfone (PSF) followed by pre-oxidation stabilization and carbonization. Addition of PSF as a sacrificial polymer leads to CNFMs with high surface area, large numbers of micropores and mesopores, good degree of carbonization, and interconnected fibrous network, due to the high decomposition temperature, release of SO₂ during decomposition, and large amount of carbon residue of PSF during carbonization. The electrochemical characterization shows that the CNFM electrode has a specific capacitance of 272 F g⁻¹ at a current density of 1 A g⁻¹ with 74% of the specific capacitance retained at 50 A g⁻¹ in 2.0 M KOH electrolyte. The CNFM electrodes have excellent cycling durability with 100% capacitance retention after 10 000 cycles.

Carbon nanofibrous mats (CNFMs) are prepared by electrospinning of blended precursor of polyacrylonitrile and polysulfone (PSF) followed by pre-oxidation stabilization and carbonization.     

Highly tough and rapid self-healing dual-physical crosslinking poly(DMAA-co-AM) hydrogel

Introducing double physical crosslinking reagents (i.e., a hydrophobic monomer micelle and the LAPONITE® XLG nano-clay) into the copolymerization reaction of hydrophilic monomers of N,N-dimethylacrylamide (DMAA) and acrylamide (AM) is reported here by a thermally induced free-radical polymerization method, resulting in a highly tough and rapid self-healing dual-physical crosslinking poly(DMAA-co-AM) hydrogel. The mechanical and self-healing properties can be finely tuned by varying the weight ratio of nanoclay to DMAA. The tensile strength and elongation at break of the resulting nanocomposite hydrogel can be modulated in the range of 7.5–60 kPa and 1630–3000%, respectively. Notably, such a tough hydrogel also exhibits fast self-healing properties, e.g., its self-healing rate reaches 48% and 80% within 2 and 24 h, respectively.

Introducing a micelle and LAPONITE® XLG nano-clay into N,N-dimethylacrylamide (DMAA)/acrylamide (AM) copolymerization reactions results in a highly tough and rapid self-healing dual-physical crosslinking poly(DMAA-co-AM) hydrogel.     

Synthesis of poly (N-isopropylacrylamide)-co-(acrylic acid) microgel-entrapped CdS quantum dots and their photocatalytic degradation of an organic dye

CdS quantum dots (CdSQDs) were generated inside the network structure of poly (N-isopropylacrylamide)-co-(acrylic acid) (pNIPAm-co-AAc) microgels and their ability to photocatalytically degrade organic dyes was evaluated using rhodamine B (RhB). The microgel-stabilized CdSQDs were generated by first enriching the microgels with Cd²⁺ followed by their reaction with Na₂S. The resultant microgels were characterized, and the CdSQDs were found to be distributed throughout the microgels. We went on to show that the hybrid microgels exhibited photocatalytic properties by exposing them to a solution of RhB followed by exposure to UV irradiation. We found that the hybrid microgels were able to degrade the RhB, while native microgels without CdSQDs present were not capable of the same behavior. Due to the thermo- and pH-responsivity of pNIPAm-co-AAc-based microgels their ability to degrade RhB was also evaluated as a function of environmental temperature and solution pH. We showed that the removal efficiency was highest when the microgels were in their swollen state, which we attribute to more effective mass transfer of the RhB inside the microgels when their porous structure is expanded. Finally, we show that the hybrid microgels can be reused multiple times, although their photocatalytic degradation ability decreases the more they are used, which may be a result of the aggregation and decomposition of the CdSQDs. We conclude that this approach is an effective means of removing RhB from water, which may be modified to photodegrade a variety of other organic compounds.

CdS quantum dots (CdSQDs) were generated inside the network structure of poly (N-isopropylacrylamide)-co-(acrylic acid) (pNIPAm-co-AAc) microgels and their ability to photocatalytically degrade organic dyes was evaluated using rhodamine B (RhB).     

Construction of a ternary system: a strategy for the rapid formation of porous poly(lactic acid) fibers

Combining electrospinning technology with nonsolvent induced phase separation (ESP-NIPS), 10 wt% poly(lactic acid) (PLA) spinning solutions are prepared by using chloroform as a good solvent and absolute ethanol as a nonsolvent. The “PLA/CHCl₃/C₂H₅OH” ternary system is constituted to realize the rapid preparation of porous-structured PLA fibers. The morphologies, thermal properties and crystalline structures of the obtained fibers are characterized and the rapid forming mechanism of PLA porous fibers is investigated and discussed. The interaction parameters between the substances of the “PLA/CHCl₃/C₂H₅OH” ternary system, binodal line, spinodal line and critical point are obtained by theoretical calculation and experiment, and the “PLA/CHCl₃/C₂H₅OH” ternary phase diagram model is established. The results show that, when the mass ratio of chloroform/ethanol is around 75/25, the rapid “in situ” formation of the PLA fibers can be realized with porous structures within 5–10 s. The establishment of a “nonsolvent-solvent–polymer” ternary phase diagram model has laid a theoretical foundation for the rapid formation of polymer porous fibers by ESP-NIPS. The ESP-NIPS for the porous PLA fibers preparation provides a new resolution for the rapid formation of porous polymer materials, which is vital to further expand the application of electrospun fibers in emergency situations such as isolation, protection, insulation and flame retardant usage.

Combining electrospinning technology with ESP-NIPS, using chloroform as a solvent and absolute ethanol as a nonsolvent, poly(lactic acid) porous fibres are prepared within 5–10 s. This preparation provides a new resolution for the rapid formation of porous polymer materials.     

Sustainable production of curable maltodextrin-based electrospun microfibers

Maltodextrins are inexpensive, water-soluble starch hydrolysis products composed of high molecular weight polysaccharide molecules. This feature allows their water solutions to be processed by electrospinning to produce bio-based microfibrous mats. Also, the presence of hydroxyl functions along the maltodextrin''s backbone enables cross-linking reactions to be performed, necessary to overcome the intrinsic solubility of the starting material, by exploiting suitable functional molecules. In this work, the electrospinning process to obtain fibre deposition from water solutions of five different commercial maltodextrins was firstly optimized. Well-defined fibres with diameters ranging between 1.1 μm and 1.5 μm were successfully obtained using water as the unique solvent. Subsequently, the same maltodextrin-containing water solutions with citric acid added were then processed again. The presence of citric acid did not hinder the spinnability of the studied systems, while the possibility to achieve a one-step thermal curing of the obtained fibres was proved via solubility tests, TGA, and FTIR-ATR analyses. Eventually, bio-based cross-linked mats with fibre diameters ranging from 0.7 μm to 1.4 μm were obtained from the electrospinning of commercial maltodextrins and citric acid, employing water as the unique solvent and environmentally friendly curing processes. This approach enables the reported mats to be further studied for environmental, pharmaceutical, and medical applications.

This paper reports a sustainable approach to obtain thermally curable bio-based microfibrous mats from the electrospinning of water solutions containing commercial maltodextrins and citric acid.