Microporous Poly Research Articles

Palladium Nanoparticles Hosted in Poly(ethylenimine) and Poly(ethylene glycol methacrylate phosphate) Anchored Membranes for Catalyzing Uranyl Ions Reduction and Mizoroki–Heck Coupling Reaction

The poly(ethylenimine) (PEI) and poly(ethylene glycol methacrylate phosphate) (poly(EGMP)) functionalized microporous poly(propylene) membrane have been developed to host the palladium (Pd) nanoparticles (NPs) for catalyzing the inorganic and organic reactions. These functionalized membranes are characterized for their porosities and pore-size distributions. Field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-rays spectrometry (EDX) attached to FE-SEM, and small-angle X-rays scattering (SAXS) have been used to study the Pd NPs size distributions and homogeneous distributions in the membrane matrixes. The average size of Pd NPs has been found to be ≈2 nm in all the membranes by SAXS experiments, and elemental mappings by EDX suggest uniform distributions of Pd NPs. However, a very small number of bigger particles have been formed in the membrane having lowered pore-filling due to lower network elasticity in some region that allowed agglomeration to some extent. The in situ generated H...

Modulation of the mechanical, physical and chemical properties of polyvinylidene fluoride scaffold via non-solvent induced phase separation process for nerve tissue engineering applications

The aim of this research was to develop microporous poly(vinylidene fluoride) (PVDF) scaffolds with an intrinsic electrical property, via the combination of non-solvent induced phase separation (NIPS) and thermal induced phase separation (TIPS) process referred as N-TIPS method. For this purpose, the effects of non-solvent incorporation (distilled water) in the solvent composition (N,N-dimethylformamide (DMF)), immersion time at coagulation bath (1, 3, 6 and 24 h) as well as coagulation bath temperature (−10, 0 and 20 °C) and composition (DMF:water volume ratio = 2:6 and 6:4) on the properties of the produced scaffolds were investigated. Results confirmed that N-TIPS processing parameters had a profound effect on the morphological, mechanical, physical and thermal properties of the PVDF scaffolds. For instance, with increased bath temperature, the formation of three-dimensional bi-continuous scaffold with average pore size of 4.2 ± 0.6 μm was achieved, whereas increase in the immersion time in coagulation bath from 1 to 24 h induced cellular morphology with a larger pore size. The formation of relatively small pore size and uniform foam-like structure at 3 h soaking in coagulation bath showed to improved mechanical properties of the scaffolds. It was also found that toughness of the scaffolds significantly promoted from 27.5 ± 16.4 MPa (after 1 h soaking) to 155.2 ± 25.4 MPa (after 3 h soaking). Moreover, depending on the functional parameters of N-TIPS process, β phase fraction and crystallinity of the PVDF scaffolds were in the range of 61–87% and 30–47%, respectively. Remarkably, 3 h soaking of PVDF polymer solution in coagulation bath with composition of 6:4 (D-3h-64 scaffold) significantly enhanced the crystallinity (47.03%) and β phase fraction (87.9%) and reduced crystallite size of PVDF polymer. The PC12 cell attachment and proliferation on PVDF scaffolds prepared at various parameters were also investigated. Noticeably, D-3h-64 scaffold with enhanced crystallinity and β phase fraction and significantly higher toughness could promote cell spreading and proliferation. The results presented in this study show a great potential of PVDF scaffolds with desired properties for nerve tissue engineering application.

Biomaterial scaffolds for non-invasive focal hyperthermia as a potential tool to ablate metastatic cancer cells

Currently, there are very few therapeutic options for treatment of metastatic disease, as it often remains undetected until the burden of disease is too high. Microporous poly(ε-caprolactone) biomaterials have been shown to attract metastasizing breast cancer cells in vivo early in tumor progression. In order to enhance the therapeutic potential of these scaffolds, they were modified such that infiltrating cells could be eliminated with non-invasive focal hyperthermia. Metal disks were incorporated into poly(ε-caprolactone) scaffolds to generate heat through electromagnetic induction by an oscillating magnetic field within a radiofrequency coil. Heat generation was modulated by varying the size of the metal disk, the strength of the magnetic field (at a fixed frequency), or the type of metal. When implanted subcutaneously in mice, the modified scaffolds were biocompatible and became properly integrated with the host tissue. Optimal parameters for in vivo heating were identified through a combination of computational modeling and ex vivo characterization to both predict and verify heat transfer dynamics and cell death kinetics during inductive heating. In vivo inductive heating of implanted, tissue-laden composite scaffolds led to tissue necrosis as seen by histological analysis. The ability to thermally ablate captured cells non-invasively using biomaterial scaffolds has the potential to extend the application of focal thermal therapies to disseminated cancers.

Molecular structure design of conjugated microporous poly(dibenzo[b,d]thiophene 5,5-dioxide) for optimized photocatalytic NO removal

Conjugated microporous polymers with high BET surface areas and a tunable bandgap are promising candidates for photocatalytic NO removal in the solid–gas phase reaction system. Herein, we report that three conjugated microporous poly(dibenzo[b,d]thiophene 5,5-dioxide) (B-DT-1,3,5; B-DT-1,2,4; B-DT-1,2,4,5) consisting of alternating electron-rich and electron-deficient units with ethynyl linker have been synthesized, and optical bandgaps varied from 2.29 eV to 2.79 eV by adjusting the position and number of CC connected to the 3D center benzene. Combined with intrinsic merits including facile tunable bandgap and high BET surface areas, the synthesized CMP(B-DT) proved to be good photocatalysts for photocatalytic NO removal. The NO removal efficiency of B-DT-1,3,5 reached up to 56% with good stability. Active species scavenger experiments and other characterizations indicated that the superior photocatalytic NO removal ability of B-DT-1,3,5 may arise from the synergistic effect of stronger hole oxidation ability, greater amounts of O2− and 1O2, and higher BET surface area. Thus, our proof-of-concept design of conjugated microporous polymers was used for a highly efficient photocatalytic NO removal in the solid-gas phase.

Electroionic Antagonistic Muscles Based on Nitrogen-Doped Carbons Derived from Poly(Triazine-Triptycene).

Electroactive soft actuators and bioinspired artificial muscles have received burgeoning interest as essential components in future electronic devices such as soft haptic‐feedback systems, human‐friendly wearable electronics, and active biomedical devices. However, important challenging issues including fast response time, ultralow input power, robust operation in harsh environments, high‐resolution controllability, and cost‐effectiveness remain to be resolved for more practical applications. Here, an electroionic antagonistic artificial muscle is reported based on hierarchically porous nitrogen‐doped carbon (HPNC) electrodes derived from a microporous poly(triazine‐triptycene) organic framework (PtztpOF). The HPNC, which exhibits hierarchically micro‐ and mesoporous structures, high specific capacitance of 330 F g−1 in aqueous solution, large specific surface area of 830.46 m2 g−1, and graphitic nitrogen doping, offers high electrical conductivity of 0.073 MS m−1 and outstanding volumetric capacitance of 10.4 MF m−3. Furthermore, it is demonstrated that a novel electroionic antagonistic muscle based on HPNC electrodes successfully displays extremely reliable and large bending deformations and long‐term durability under ultralow input voltages. Therefore, microporous polymer or covalent organic frameworks can be applied to provide significant improvements in electroactive artificial muscles, which can play key roles as technological advances toward bioinspired actuating devices required for next‐generation soft and wearable electronics.

High permeance nanofiltration thin film composites with a polyelectrolyte complex top layer containing graphene oxide nanosheets

A graphene oxide (GO) nano-additive was incorporated into a polyelectrolyte complex (PEC) to prepare water selective membranes for a water desalination process. The synthesized thin film composites consisted of a PEC-GO separation layer, a microporous poly(vinylidene fluoride) layer, and a non-woven substrate. The crosslinking agent glutaraldehyde (GA) was used to enhance the stability of the PEC composite membranes. The resulting membranes were investigated in nanofiltration systems to examine their permeance and salt rejection efficiency. The results demonstrated that 100ppm GO in the PEC exhibited a high desalination efficiency on a 1000ppm NaCl solution. This composite exhibited permeance values in the range of 69–89kgm−2h−1MPa−1 for various salt solutions. The Na2SO4 solution resulted in the highest rejection ratio of 62.1%, followed by the NaCl rejection (38.6%). The MgCl2 and MgSO4 solutions had lower rejections of 12.2% and 22.0%. It seems that the GA_PEC-GO composite was more efficient in removing divalent ions than monovalent ions, while maintaining high filtration flux.

Self-Healing Hydrogel Pore-Filled Water Filtration Membranes

Damages to water filtration membranes during installation and operation are known to cause detrimental loss of the product water quality. Membranes that have the ability to self-heal would recover their original rejection levels autonomously, bypassing the need for costly integrity monitoring and membrane replacement practices. Herein, we fabricated hydrogel pore-filled membranes via in situ graft polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto microporous poly(ether sulfone) (PES) substrates and successfully demonstrated their self-healing ability. Covalent attachment of the hydrogel to the substrate was essential for stable membrane performance. The membranes autonomously restore their particle rejection up to 99% from rejection levels as low as 30% after being physically damaged. We attribute the observed self-healing property to swelling of the pore-filling hydrogel into the damage site, strong hydrogen bonding, and molecular interdiffusion. The results of this study show that hydrogel pore-filled membranes are a promising new class of materials for fabricating self-healing membranes.

Highly efficient visible light induced photocatalytic activity of a novel in situ synthesized conjugated microporous poly(benzothiadiazole)–C3N4 composite

Highly efficient visible light-driven heterojunction BBT–C3N4 exhibits superior redox ability for sulfathiazole and Cr(vi) removal.

Synthesis and Gas Sorption Properties of Microporous Poly(arylene ethynylene) Frameworks

Synthesis and Gas Sorption Properties of Microporous Poly(arylene ethynylene) Frameworks

PVDF-HFP/PET/PVDF-HFP composite membrane for lithium-ion power batteries

In this study, a novel polymer electrolyte composite membrane is successfully fabricated using electrospinning and solution casting. The composite membrane comprises two microporous poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) layers plus an intermediate quaternary ammonium-containing SiO2 nanoparticles modified polyethylene terephthalate (PET) nanofibrous nonwoven to form a sandwiched PVDF-HFP/PET/PVDF-HFP composite, which is employed as a separator for lithium-ion batteries (LIBs). The properties of the PET composite membrane are compared with those of commercial PE separator, such as the morphologies, physical properties, and electrochemical performances. According to our results, the composite membrane demonstrates superior thermal stability (thermal shrinkage ∼8%), electrolyte-philicity (contact angle ∼2.9°), electrolyte uptake and retention (282%, 74%), and ionic conductivity (∼10−3 S cm−1). The separators are assembled into Li/LiFePO4 cells for electrochemical tests, showing that the PET composite membrane cells exhibit higher capacities than those with the PE separator at 0.2–10C both at 25 °C and 55 °C. The discharge capacity retention and coulombic efficiency of the PET composite membrane cells at 1C/1C for 200 cycles can be respectively enhanced about 20% and 2% at 55 °C as compared to the PE separator cells. These results demonstrate that our prepared PET composite membrane is highly promising for LIB applications.

Novel in situ fabrication of conjugated microporous poly(benzothiadiazole)–Bi2MoO6 Z-scheme heterojunction with enhanced visible light photocatalytic activity

A novel conjugated microporous poly(benzothiadiazole)–Bi2MoO6 (BBT–BMO) Z-scheme heterojunction was fabricated in situ through a facile palladium-catalyzed Sonogashira–Hagihara cross-coupling polycondensation of 4,7-dibromobenzo[c][1,2,5]thiadiazole and 1,3,5-triethynylbenzene on the surface of Bi2MoO6. Characterization results illuminated that BBT was stably coated on the surface of Bi2MoO6 nanosheets with the formation of CO bonds. This novel BBT–BMO composite exhibited superior photocatalytic performance in both sulfathiazole degradation and Cr(VI) reduction compared with pure BBT and Bi2MoO6 in visible light. In line with systematic characterizations results, a reasonable photocatalytic mechanism based on direct Z-scheme heterojunction was proposed and further verified via OH determination. This Z-scheme heterojunction endowed it with improved visible light absorption, larger surface area, and greater electron–hole separation and thus efficiently enhanced the photocatalytic performance. This work provides new insight into the utilization of conjugated microporous polymers in photocatalysis and paves a new way to construct Z-scheme heterojunctions with enhanced photocatalytic performance via metal-free polymers modification.

Thiourea grafted PVDF affinity membrane with narrow pore size distribution for Au (III) adsorption: Preparation, characterization, performance investigation and modeling

Thick and hydrophilic microporous poly(vinylidene fluoride) (PVDF) affinity membranes were prepared for low-concentration gold separation by grafting thiourea on alkali treated PVDF resin. The modified polymer was easily cast into membranes by non-solvent induced phase separation through two coagulation processes, and the addition of N-methyl-2pyrrolidone into the second coagulation bath improved the pore size distribution effectively. The grafted polymer and membrane were characterized by FTIR, Raman, 1H NMR, XPS, SEM and pore size distribution measurement. Static adsorption of Au (III) with the membranes followed pseudo-second order kinetics and Langmuir isotherm. Dynamic adsorption was investigated by using stacked membranes in the form of a membrane chromatography. The results showed that increasing the number of membrane layers improved the membrane bed utilization, which was attributed to the increased adsorption sites and a combined effect of reduced average membrane pore size and narrowed pore size distribution (PSD). The effect of PSD on performance of the membrane chromatography was further separated from that of the mean pore size, and it was shown that narrower PSD indeed was favorable. A new mathematical model based on dispersive mass transfer through the membrane pores and incorporating PSD was established. The model was found to be able to predict the membrane breakthrough behavior very well. Finally, the elution performance of gold laden membrane was studied, and an optimized formulation of the eluent consisting of thiourea and HCl was determined.

Developing nanofiltration membrane based on microporous poly(tetrafluoroethylene) substrates by bi-stretching process

A thin film composite (TFC) nanofiltration membrane was fabricated through interfacial polymerization on microporous poly(tetrafluoroethylene) (PTFE) substrates, which were fabricated by bi-stretching process (longitudinal and transverse stretching). Multilayers were formed on PTFE substrate via physical twining and chemical linkage. Impacts of bi-stretching ratios on separation properties of TFC nanofiltration membrane were deeply investigated. Results indicate that the increase of longitudinal stretching ratio increased the length of fibrils and induced larger pore sizes and porosities, which resulted in lower values of rejection and higher permeate flux. However, the increase of transverse stretching ratio induced that the pore sizes declined and the porosities increased, which may be due to interlaced fibrils. Accordingly, it induced higher values of rejection and permeate flux. The obtained TFC nanofiltration membrane exhibited good acid stability (over 30 days) and high stability on long term (over 90 days). It could be potentially employed in nanofiltration process.

Conjugated microporous poly(benzothiadiazole)/TiO2 heterojunction for visible-light-driven H2 production and pollutant removal

A π-conjugated microporous poly(benzothiadiazole) (hereafter denoted as BBT) is synthesized through palladium-catalyzed Sonogashira-Hagihara cross-coupling polycondensation, and used as a novel organic semiconductor photocatalyst for both photocatalytic H2 production and pollutant degradation under visible light (λ>420nm) irradiation. Furthermore, BBT/TiO2 heterojunction is conveniently fabricated through an in-situ polycondensation procedure of 4,7-dibromobenzo[c][1,2,5]thiadiazole and 1,3,5-triethynylbenzene in the presence of commercial TiO2. After optimizing the composition ratio, the resultant BBT/TiO2 heterojunction exhibited dramatically enhanced visible-light-responsive photocatalytic activities (∼18.0 and 20.4 times higher activity for H2 evolution and ciprofloxacin degradation, respectively) as compared BBT alone. Detailed investigations revealed that the BBT/TiO2 heterojunction interface can accelerate the photogenerated electron transferring from BBT to TiO2, and then improve the photoactivity. The present work exhibits some interesting points and dramatic improvement of photoactivity when an organic semiconductor is combined with an inorganic one, which provides a novel direction to exploit and fabricate photocatalyst for solar energy conversion and pollutant degradation.

A bioengineered niche promotes in vivo engraftment and maturation of pluripotent stem cell derived human lung organoids.

Human pluripotent stem cell (hPSC) derived tissues often remain developmentally immature in vitro, and become more adult-like in their structure, cellular diversity and function following transplantation into immunocompromised mice. Previously we have demonstrated that hPSC-derived human lung organoids (HLOs) resembled human fetal lung tissue in vitro (Dye et al., 2015). Here we show that HLOs required a bioartificial microporous poly(lactide-co-glycolide) (PLG) scaffold niche for successful engraftment, long-term survival, and maturation of lung epithelium in vivo. Analysis of scaffold-grown transplanted tissue showed airway-like tissue with enhanced epithelial structure and organization compared to HLOs grown in vitro. By further comparing in vitro and in vivo grown HLOs with fetal and adult human lung tissue, we found that in vivo transplanted HLOs had improved cellular differentiation of secretory lineages that is reflective of differences between fetal and adult tissue, resulting in airway-like structures that were remarkably similar to the native adult human lung.

Enhanced Survival with Implantable Scaffolds That Capture Metastatic Breast Cancer Cells In Vivo.

The onset of distant organ metastasis from primary breast cancer marks the transition to a stage IV diagnosis. Standard imaging modalities often detect distant metastasis when the burden of disease is high, underscoring the need for improved methods of detection to allow for interventions that would impede disease progression. Here, microporous poly(ε-caprolactone) scaffolds were developed that capture early metastatic cells and thus serve as a sentinel for early detection. These scaffolds were used to characterize the dynamic immune response to the implant spanning the acute and chronic foreign body response. The immune cell composition had stabilized at the scaffold after approximately 1 month and changed dramatically within days to weeks after tumor inoculation, with CD11b(+)Gr1(hi)Ly6C(-) cells having the greatest increase in abundance. Implanted scaffolds recruited metastatic cancer cells that were inoculated into the mammary fat pad in vivo, which also significantly reduced tumor burden in the liver and brain. Additionally, cancer cells could be detected using a label-free imaging modality termed inverse spectroscopic optical coherence tomography, and we tested the hypothesis that subsequent removal of the primary tumor after early detection would enhance survival. Surgical removal of the primary tumor following cancer cell detection in the scaffold significantly improved disease-specific survival. The enhanced disease-specific survival was associated with a systemic reduction in the CD11b(+)Gr1(hi)Ly6C(-) cells as a consequence of the implant, which was further supported by Gr-1 depletion studies. Implementation of the scaffold may provide diagnostic and therapeutic options for cancer patients in both the high-risk and adjuvant treatment settings. Cancer Res; 76(18); 5209-18. ©2016 AACR.

Perfluorinated or Hydrocarbon Ionomer-Poly(tetrafluoroethylene) Reinforced Membranes for Renewable Energy Generation

Ionomers are polymeric materials containing fixed charged ions (e.g., –SO3 -) to transport their counter ions (e.g., H+, Li+, Na+ and so on) selectively and have been widely used as key materials to make ion exchange membranes for renewable energy generation (e.g., pressure-retarded osmosis, reverse electrodialysis, polymer electrolyte membrane fuel cells, and redox flow batteries). Particularly for effective power generation from salinity gradient, it is necessary to use high flux membranes with excellent ion-selectivity. High water flux can be accomplished by controlling the membrane thickness as thin as possible. However, thin membranes are suffering from high water pressure. This technical trade-off relationship may be overcome by filling ionomers into porous support films with high mechanical strength. It is, however, difficult to prepare the reinforced membranes without defects owing to ionomers solubility and compatibility issues, irrespectively of which ionomers are used. That is, perfluorinated ionomers have low solubility in most of solvents including polar aprotic solvents. The resulting membranes exhibit high brittleness. Much serious problems are observed during reinforced membrane formation using hydrocarbon ionomers. The good solvents to hydrocarbon ionomers dissolve support films, resulting in the breakdown of their pore structures. Moreover, it is important to enhance compatibility between hydrophilic ionomers and hydrophobic support films. Otherwise their interfaces may be converted into defects, which lower ion selectivity. This phenomenon is much easily observed as the pore size become smaller. In this study, a plausible approach, which is called as water-alcohol nanodispersion, was tried to obtain effective ionomers materials for defect-free reinforced membrane formation. Here, microporous poly(tetrafluoroethylene) (PTFE) support films were chosen considering chemical and thermal resistance of resulting reinforced membranes. The appropriate control of the solvent mixture contributed to high compatibility between ionomers and support films, and made spontaneous pore-impregnation possible. Interestingly, the nanodispersed ionomers resulted in much improved ion-selectivity owing to a synergistic effect of well-defined hydrophilic-hydrophobic phase-separated morphologies and high ionic density per hydrated membrane volume.

Poly(m-phenylene isophthalamide) separator for improving the heat resistance and power density of lithium-ion batteries

A microporous poly(m-phenylene isophthalamide) (PMIA) separator with high safety (high-heat resistance and self extinguishing), high porosity and excellent liquid electrolyte wettability was prepared by the traditional nonsolvent introduced phase separation process. Due to the high-heat resistance of PMIA material, the as-prepared separator exhibited a negligible thermal shrank ratio at 160 °C for 1 h. Meanwhile, benefiting from its high porosity and excellent wettability in liquid electrolyte, the liquid electrolyte uptake and the ionic conductivity of the separator were higher than that of the commercial PP-based separators. Furthermore, the cell assembled with this separator showed better cycling performance and superior rate capacity compared to those with PP-based separators. These results suggested that the PMIA separator is very attractive for high-heat resistance and high-power density lithium-ion batteries.

Tough Polymer Aerogels Incorporating a Conformal Inorganic Coating for Low Flammability and Durable Hydrophobicity.

Both inorganic and polymeric aerogels are well-known in the materials field. Inorganic aerogels are generally susceptible to brittle fracture, while polymeric aerogels tend to exhibit low modului and high flammability. To overcome these disadvantages, we introduce a new approach to the design of aerogels. A microporous poly(vinyl alcohol) (PVA) aerogel/silica nanocomposite was prepared by growing a silica conformal coating onto a PVA aerogel scaffold. Such aerogel/silica nanocomposites show significant improvement in their mechanical properties over either individual component. The nanocomposites show excellent fire resistance since the silica conformal coating serves as a barrier for heat transfer and mass loss of the coated organic materials. After a fluorocarbon silane treatment, the nanocomposites also show durable superhydrophobicity.

Effect of polar rotation on the formation of porous poly(vinylidene fluoride) membranes by immersion precipitation in an alcohol bath

Microporous poly(vinylidene fluoride) (PVDF) membranes were prepared by isothermal immersion-precipitation of PVDF/N,N-dimethylformamide (DMF) casting dopes in different alcohol baths. The formed membranes can be divided into two groups, based on the morphology and crystal type of the globular particles constituting the membrane matrix. The particles in the first group of membranes appear like a hydrangea flower composed of petal-like crystal lamellae. It was formed when precipitation was carried out in a lower-carbon alcohol bath, e.g. 1- or 2-propanol. On the other hand, when higher alcohol bath such as 1-butanol or 1-octanol bath was used as the coagulant, the formed membranes (group II) comprised compact globules whose surfaces were covered with granular identities of ca. 30nm dia. XRD and FTIR-ATR analyses of the membranes indicate that group I membranes contain both α- and γ-type crystals, whereas group II membranes contain only γ-type crystals. Transformation of PVDF chains from γ– to α– conformation due to dipole rotation during membrane formation was delineated by 19F NMR spectroscopy. The crystallinities of the membranes were determined both by diffraction peak deconvolution and differential scanning calorimetry. Both methods indicated that the group I membranes had a crystallinity of ca. 66%, which was 5% lower than that of the group II membranes.