Hydrophilic Polyethyleneimine Research Articles

Ultrafiltration study of the polysulfone membrane modified with branched polyethyleneimine

Abstract This work discussed the fabrication of polysulfone (PSF) ultrafiltration membranes with hydrophilic behaviour by adding branched polyethyleneimine (PEI) as an additive. By directly blending the base polymer and the additive in the organic solvent, the casting solution is prepared. An asymmetric ultrafiltration membrane was fabricated by the phase inversion method. The presence of PEI was confirmed by comparing the IR spectra of the plain PSF membrane and the modified PSF membrane. A scanning electron microscope was used for the comparison of morphological changes in plain and modified membranes. The membrane was characterised with respect to bovine serum albumin (BSA) adsorption, pure water flux, permeability, compaction factor, humic acid (HA) rejection, and water uptake. The fouling resistance behaviour is prompted due to the presence of hydrophilic PEI chains in the membrane. As a result, pure water flux and flux recovery ratio increased from 28.84 to 326.54 L/m2h and from 0.526 to 0.954 L/m2hkPa for the modified membrane with respect to the plain membrane, respectively.

Balancing gene transfection and cytotoxicity of nucleic acid carriers with focus on ocular and hepatic disorders: evaluation of hydrophobic and hydrophilic polyethyleneimine derivatives.

Polyethyleneimine (PEI) derivatives substituted by lactose, succinic acid or alkyl domains were evaluated as nonviral gene delivery vectors towards balancing gene transfection and cytotoxicity. The investigations were focused on pDNA transfection into arising retinal pigment epithelia (ARPE-19) and human hepatocellular carcinoma (HepG2) cell lines. The first mentioned cell line was chosen as motivated by the non-negligible number of ocular disorders linked to gene aberrations, whereas the second one is a cell line overexpressing the asialoglycoprotein receptor (ASGP-R), which can bind to galactose residues. The presence of short alkyl domains (C4 and C6), and particularly the succinylation of the PEI chains, improved the biological outputs of the gene vectors. The presence of hydrophobic units possibly enhances lytic activity, whereas the incorporation of succinic acid slightly reduces polymer-DNA interaction strength, thereby enabling more efficient intracellular unpacking and cargo release. Succinylation is also supposed to decrease cytotoxicity and avoid protein adsorption to the polyplexes. The presence of long carbon chains (for instance, C12) nevertheless, results in higher levels of cytotoxicity and respective lower transfection rates. The sugar-decorated polyplexes are overall less cytotoxic, but the presence of lactose moieties also leads to larger polyplexes and notably weak polymer-DNA binding, which compromise the transfection efficiency. Yet, along with the presence of short lytic alkyl domains, the double-substitution of PEI synergistically boosts gene transfection probably due to the uptake of higher DNA and polymer amounts without cell damage. Overall, the experimental data suggest that ocular and hepatic gene therapies may be potentialized by fine-tuning the hydrophobic-to-hydrophilic balance, and succinic acid is a favorable motif for the modification of PEI.

Heterostructured membranes with selective solvent-capture coatings and low-resistance 2D nanochannels for efficient mixed solvent separation

Two-dimensional lamellar membrane with well-defined nanostructure shows exceptional molecule permeation and precise sieving, holding promise for mixed solvent separation. Herein, heterostructured membranes with selective solvent-capture polymer coatings on MXene-based lamellar membrane surface were prepared for separation of polar/nonpolar solvents. The thin polymer coatings selectively capture solvents from mixed solvents, and the inner laminates promote their fast transport, therefore realizing efficient separation. Specifically, hydrophilic polyethyleneimine (PEI) coating captures polar solvents and promotes them into hydrophilic laminates, where they form orderly aligned aggregates along nanochannel walls and diffuse fast. While the behaviors are inverse for nonpolar solvents due to the repelled dissolution from PEI and slow diffusion in nanochannels. This synergistic effect offers high permeance of 413 L m−2h−1 bar−1 with separation factor of 4.5 for toluene/acetonitrile mixture. Similarly, hydrophobic polydimethylsiloxane coating captures nonpolar solvents and facilitates their transport in hydrophobic laminates, allowing concentration of nonpolar solvents with separation factor of 4.7 for toluene/methanol mixture. Besides, the heterostructured membranes exhibit acceptable structural and operational stability. This initiatory attempt of separating mixed solvents should help bordering the practical applications of 2D lamellar membranes.

Fabrication of anti‐fouling thin‐film composite reverse osmosis membrane via constructing heterogeneous wettability surface

AbstractAnti‐fouling properties are tightly related to the surface properties of reverse osmosis (RO) membranes. In our study, fluorinated polyethyleneimine (FPEI) was synthesized by introducing perfluoroalkyl groups into a hydrophilic polyethyleneimine (PEI) matrix, and the heterogeneous wettability surface with hydrophilic and low‐surface‐energy properties was constructed by grafting FPEI on membrane surface via the carbodiimide‐induced method. Verified by the result analysis of SEM, AFM, and zeta potentials measurements, the fluorinated RO membrane surface presented denser, smoother, and reduced negative charge. The surface free energy of RO membrane surface after grafting FPEI decreased from 45.5 to 38.7 mJ/m2. By using bovine serum albumin (BSA), humic acid (HA), and dodecyltrimethyl ammonium bromide (DTAB) as model foulants, the fluorinated RO membrane exhibits optimal fouling resistance and fouling release properties compared to pristine membrane and membrane modified by surface grafting hydrophilic PEI. Especially, the high recovery ratio (99%) and low total flux decline ratio (17.2%) were acquired during the filtration of BSA solution. These results manifested that the construction of a heterogeneous wettability surface can further improve the anti‐fouling properties of RO membranes compared to a pure hydrophilic surface, and the corresponding anti‐fouling mechanism was put forward.

Preparation of Stable Hydrophilic Polyethyleneimine Cross-Linked Graphene Oxide/Titanium Dioxide Membranes for Dye Separation

An excellent novel laminar and hierarchical polyethyleneimine cross-linked graphene oxide/titanium dioxide (GO–TiO2–PEI) membrane was successfully prepared by vacuum filtration technology using polyethyleneimine (PEI) as the cross-linking agent and a GO–TiO2 nanocomposite as the substrate. The resultant membrane (GO–TiO2–PEI) displayed a favorable antifouling performance with bovine serum albumin (BSA) and showed good hydrophilicity and wettability, with a static water contact angle of 13.2∘. The stability of the GO–TiO2–PEI membrane in aqueous solution obviously improved with the cross-linking of PEI compared with that of the GO and GO–TiO2 membranes. The GO–TiO2–PEI membrane also exhibited a satisfactory water flux of 48.6[Formula: see text]L m[Formula: see text] h[Formula: see text] bar[Formula: see text]. The GO–TiO2–PEI membrane exhibited a good performance for effectively separating different dyes including methylene blue (MB), rhodamine B (RB), methyl orange (MO), sunset yellow (SY), new coccine (NC) and amaranth. All the above results suggested that the GO–TiO2–PEI membrane could be used as an excellent stable hydrophilic membrane for efficiently separating dyes from aqueous solution.

Constructing large loadings of dual pathways with Ti3C2Tx-CDs in thin film nanocomposite membrane for enhanced organic permeation

Dual pathways hold great superiority in facilitating molecular permeation for various separation applications. However, the existing dual-pathway nanostructure fails in realizing large loadings of dual pathways and hence limited molecular permeation. Here, cyclodextrins (CDs) with hydrophilic exterior surface but strong hydrophobic interior cavity are utilized and anchored on Ti3C2Tx nanosheets, thus constructing large loadings of dual pathways. The resultant building blocks (Ti3C2Tx-CDs) are integrated into hydrophilic polyethyleneimine (PEI) matrixes to prepare thin film nanocomposite (TFN) membranes. Ti3C2Tx-CDs offer the advantage of forming large loadings of dual pathways by anchoring quantities of CDs on Ti3C2Tx nanosheets, thanks to the abundant –OH groups of Ti3C2Tx nanosheets. The hydrophobic internal cavities of CDs work as transfer highways for nonpolar solvents, while hydrophilic PEI matrixes afford for polar solvents, imparting to the membranes enhanced organic permeation. For isopropanol, TFN-Ti3C2Tx-β-CDs attains the permeation of 3.8 L m−2 h−1 bar−1. For n-heptane, more striking augment in permeation is observed for TFN-Ti3C2Tx-β-CDs, reaching 2.7 L m−2 h−1 bar−1, 9 times of control membrane (TFN-Ti3C2Tx) value. Moreover, these TFN membranes display superior structural stability, guaranteeing great potential for applications in sophisticated organic solvent systems.

Synergistic flame retardancy of aqueous hybridization between iron phosphonate and ammonium polyphosphate towards polyethyleneimine-based foam

A hybrid flame retardant, of excellent stability in aqueous media, was designed to develop flame-retarded polyethyleneimine (PEI) foam. In this case, iron phosphonate (FeP) with carboxyl group and hydroxyl group was first designed and synthesized. The carboxyl group could be hydrogen bonded with the water-soluble ammonium polyphosphate (APP) in aqueous media, and then dispersed as nano-sized particles. Subsequently, the well-dispersed nano-hybrid of FeP and APP (FeP/APP) was blended with hydrophilic PEI to prepare a kind of composite foam through a freeze-drying process. For FeP/APP, the transition metal iron showed excellent catalytic carbonization performances. Meanwhile, APP could also catalyze the degradation of polymers to form a protective char layer. The thermogravimetric analysis coupled with Fourier transform infrared analysis (TG-FTIR) test disclosed that the improvement of flame retardancy for PEI-based foams was ascribed to the synergistic effect of FeP and APP in the condensed phase. The composite foam containing 30 wt% FeP/APP could self-extinguish and reach V-1 rating in UL-94 test. When the loading level of 45% FeP/APP reached 45%, the composite foam could elevate up to V-0 rating, and the peak of heat release rate and total heat release were reduced by 71.8% and 74.2%, respectively, compared to a neat PEI foam. It is worth noting that our work presents a promising way for preparation of stable aqueous flame retardant, and is expected to enhance the fire safety of aqueous foams, coatings, cotton textiles, and other flammable materials.

Amino-functionalized polymethylmethacrylate-co-polyethyleneimine (PMMA-co-PEI) as a template to fabricate nano-silica

Polymer template method is a general and facile to fabricate nano-structural matters. Some amphiphilic polymers or co-polymers were used as templates to synthesize nano-silica. In this contribution, polymethacrylate (PMMA) employed was a commercial hydrophobic acrylate polymer and grafted with a strong hydrophilic polyethyleneimine (PEI, a densely amino-groups polymer) via aminolysis reaction, which was monitored and identified by means of FT-IR. The aminolysis reaction was optimized and the suitable reaction time was 12 h at 110 °C. The obtained copolymer, PMMA-co-PEI was applied as a template to prepare nano-silica spheres that was characterized by a scanning electron microscope (SEM). When the dosage was 1 wt% of purified PMMA-co-PEI, the resultant nano-silica had uniform particle size, and average diameter of 311 nm. When the dosage of PMMA-co-PEI was increased to 2 wt% or 4 wt%, the resultant particles became bigger and inclined to aggregate. Nano-silica afforded by this template method will be a promising material in application of catalysis, energy, biology and chromatographic analysis and the copolymer of PMMA-co-PEI will be a template for producing metal oxide nano-spheres.

Fabrication of superhydrophilic and underwater superoleophobic membranes via an in situ crosslinking blend strategy for highly efficient oil/water emulsion separation

Poly(methyl methacrylate-co-glycidyl methacrylate) P(MMA-co-GMA) and polyethyleneimine (PEI) were blended with poly(vinylidene fluoride) (PVDF) via phase separation and allowed to undergo in situ crosslinking copolymerization to produce a superhydrophilic and underwater superoleophobic membrane for oil/water emulsion separation. The P(MMA-co-GMA) copolymer served as a crosslinker for the crosslinking copolymerization of the hydrophilic PEI polymer. Both of these polymers were chosen to reduce losses of the hydrophilic polymers typically encountered during membrane preparation. The successful preparation of these coatings was demonstrated by TGA, SEM, ATR-FTIR and XPS characterization. Blending with the hydrophilic components significantly improved the hydrophilicity of the blend PVDF membranes. The membrane became superhydrophilic and superoleophobic underwater while also exhibiting underwater anti-oil-fouling performance. The blend PVDF membrane can intercept the oil droplets while allowing water to pass through, exhibiting excellent performance for oil/water emulsion separations. In addition, the blend PVDF membrane withstands repeated use and long-term operation due to the in situ crosslinking strategy employed.

Layer-by-layer assembled carbon nanotube-polyethyleneimine coatings inside copper-sintered heat pipes for enhanced thermal performance

Biporous structures at the nano–microscale are promising candidates for controlling phase change heat transfer, through their enhanced capillary wicking and fluid transportation. However, existing methods for fabricating biporous structures involve complex process which is not suitable for small-scale thermal devices such as heat pipes, owing to their confined and non-flat inner structures. Herein, we report the biporous structures inside copper-sintered heat pipes, enabled by layer-by-layer (LbL) assembled multi-walled carbon nanotube (MWCNT)-polyethyleneimine (PEI) coating for enhanced thermal performance. The repetitive filling and removing of the oppositely charged solutions with MWCNT-PEI and carboxylic-functionalized MWCNTs assembled the nanoporous MWCNT-PEI coatings (10, 20, and 40 bilayers) on the microporous copper-sintered inner surfaces. The fiber-like MWCNT networks structurally manipulated morphology and thickness of biporous structures, while the hydrophilic PEI shells chemically optimized wettability. A reduced thermal resistance (∼14.3%) was observed for MWCNT-PEI coating in 10 bilayers, due to the enhanced capillary wicking, interfacial contact areas, and bubble dynamics, whereas the 40 bilayers did not exhibit improved thermal performance owing to the redundant nanoporous layers causing reduced volume of microporous structures and increased thermal resistance. The LbL-assembled MWCNT-PEI coatings would act as functional layers to improve the performance of miniaturized and thin-film-based thermal devices.

Polyethylenimine modified silica nanoparticles enhance interfacial interactions and desalination performance of thin film nanocomposite membranes

Thin film composite (TFC) membranes incorporated with inorganic nanoparticles into the polyamide layer have recently gained great research interests. However, the incompatibility of introduced nanoparticles and their instability in the TFC membranes are the main challenges. It has been questioned that how the hybridized nanoparticles could sustainably enhance the overall desalination performance within the complex filtration mechanisms in terms of water permeability and salt rejection, as well as mechanical strength of the membranes. Herein, hydrophilic polyethylenimine (PEI) modified silica nanoparticles (SN), noted as SN-PEI, are synthesized with the aim to fabricate SN-PEI hybridized thin film nanocomposite (TFN) membranes for desalination. The successful incorporation of SN-PEI into the TFC membranes is confirmed through characterization techniques. The functional SN-PEI showed promising chemical characteristics to enhance interfacial molecular interactions between the SN and polymer matrix which improve the compatibility of SN with the polymer structure and the mechanical properties of the TFN membranes. Higher hydrophilicity of the TFN membranes due to the SN-PEI incorporation is beneficial for enhancing water molecular transfer through the membrane. Our experimental and statistic data revealed that the SN-PEI hybridized TFN membranes demonstrated up to 46% improvement in water flux, higher salt rejection, and improved mechanical strength compared to the control TFC membranes. Higher hydrophilicity of the TFN membranes due to the SN incorporation is beneficial for enhancing water molecular transfer and antifouling resistance for cost reduced desalination.

Development of polyethyleneimine-loaded core-shell chitosan hollow beads and their application for platinum recovery in sequential metal scavenging fill-and-draw process

Polyethyleneimine (PEI)-loaded chitosan hollow beads (CHBs) were fabricated through the ionotropic gelation process using sodium tripolyphosphate (TPP) as a counter polyanion. The CHBs were loaded with hydrophilic PEI in pre- and/or post-loading methods. Hence, the sorbent could possess a large number of amine groups which were able to function as the binding sites to recover platinum metal ions. The enhancement of the amine groups was confirmed by Fourier transform infrared spectroscopy (FTIR). Isotherm and kinetic studies were carried out to evaluate the sorption performance of the sorbents. The maximum Pt(IV) uptake by the PEI-loaded CHBs was estimated to be 815.2±72.6mg/g, which was much higher than that of a commercial ion exchange resin, Lewatit® MonoPlus TP214 (330.2±16.6mg/g). A sequential metal scavenging fill-and-draw process was operated using the PEI-loaded CHBs sorbents for ten cycles and the Pt(IV) recovery efficiency was kept above 97.4% even after the last cycle. These results indicated that the ionic polymer-loaded hydrogel hollow beads can be a novel platform to design high-performance sorbents able to recover and/or scavenge anionic precious metal ions even from trace metal solutions.

Polymer-Ti3C2Tx composite membranes to overcome the trade-off in solvent resistant nanofiltration for alcohol-based system

Solvent resistant nanofiltration (SRNF) technology is an energy efficient and environmentally friendly alternative to purify alcohol-based mixtures, but there exists a challenge in overcoming the trade-off between membrane flux and rejection. Herein, as the representative of the emerging family of MXenes, Ti3C2Tx nanosheets with abundant –OH groups are chosen as nanofillers to prepare SRNF composite membrane after being incorporated into two typical polymer matrixes: hydrophilic polyethyleneimine (PEI) and hydrophobic polydimethylsiloxane (PDMS). Systematic characterizations and measurements suggest that the uniformly dispersed Ti3C2Tx nanosheets enhance the thermal/mechanical stabilities and solvent resistance for both polymer-based membranes through steric effects and/or interfacial interactions. Besides, the horizontally-lied Ti3C2Tx nanosheets give significant promotion on the transfer of alcohol molecules by providing additional pathways along nanosheet surface using –OH as adsorption site. Particularly, they afford improvements of alcohol flux as high as 30% to PEI-based membrane and 162% to PDMS-based membrane. Meanwhile, the rejection abilities are dramatically improved with MWCOs below 200Da due to the blockage of solute transfer by the nanosheets. These results indicate that the trade-off between alcohol flux and solute rejection is readily overcome. The transfer properties of weak- or non-polar solvents and the long-term operation stability of membranes are also explored.

Surface modified graphene oxide/poly(vinyl alcohol) composite for enhanced hydrogen gas barrier film

A series of novel polyethyleneimine (PEI) modified graphene oxide (PEI-mGO) filled poly(vinyl alcohol) (PVA) nanocomposite (PEI-mGO/PVA) films were prepared by solution-casing for hydrogen gas barrier applications. Hydrophilic PEI was used to simultaneously reduce and modify graphene oxide sheets, thereby facilitating a homogeneous dispersion of PEI-mGO in the PVA matrix. The effects of PEI-mGO on the morphology and properties of the nanocomposite films were examined by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and field emission scanning electron microscopy. Analogous GO/PVA composites were also prepared and characterized for comparative purposes. The PEI-mGO/PVA nanocomposites showed higher thermal and mechanical stability as well as remarkable improvement in hydrogen gas barrier properties compared to the PVA film; specifically, the PEI-mGO/PVA film having 3.0 wt% of PEI-mGO content exhibited almost 95% decrease in GTR and permeability values compared to PVA film.

Facile synthesis of gold/polymer nanocomposite particles using polymeric amine-based particles as dual reductants and templates

Herein we report a facile synthesis of gold nanoparticle/polymer nanocomposite particles through a spontaneous reduction of tetrachloroauric (III) acid and encapsulation of resultant gold nanoparticles using amine-rich polymeric particles in water. The particle consisted of core–shell nanostructure with a dense layer of polyethyleneimine (PEI) shell. The hydrophilic PEI shell acted as a reductant to generate gold nanoparticles (AuNPs), while the particle as a polymer template to in-situ encapsulate and stabilize the resultant AuNPs, giving a stable gold/polymer nanocomposite particle in water. The PEI-based core–shell particles with different degree of softness were found to have little influence on the reduction ability of the gold salt, but considerablely affect the encapsulating capability. Increasing the level of softness of particle core gave higher encapsulation efficiency to the gold nanoparticles. A soft type of core–shell microgel, namely poly(N-isopropyl acrylamide)/polyethyleneimine (PNIPAm/PEI) was further investigated with respect to the reduction rate, encapsulation efficiency, as well as nanocomposite stability and properties. Results indicated that reduction rate of gold salts using the PNIPAm/PEI microgels as the reductant was two orders of magnitude faster than that of the native PEI. Solution pH and amine to gold salt ratio also affected the formation of Au@PNIPAm/PEI composite particles. Our results demonstrate that the use of polymeric amine-based particles is a simple and green synthesis of Au@polymer nanocomposite particles in aqueous system which is free from organic solvent, reducing and stabilizing agents.

Tuning the Performance of Composite Membranes by Optimizing PDMS Content and Cross-Linking Time for Solvent Resistant Nanofiltration

Herein, a series of composite membranes with optimized solvent permeance and rejection are prepared by combining the advantages of hybridization and cross-linking techniques. Polyethylenimine (PEI) and hydroxyl terminated trifluoride polydimethylsiloxane (PDMS) are cross-linked with trimesoyl chloride as the skin layer, which is isotropic rather than hierarchical. The chain mobility of PEI is inhibited upon hybridization and cross-linking, affording enhanced solvent resistance and thermal/mechanical stabilities. The composite membrane achieves high rejection ability with the rejection of PEG 1000 of about 100%. Additionally, the synergy of hydrophilic PEI and hydrophobic PDMS segments gives acceptable solvent permeances for acetone (up to 2.7 L m–2 h–1 bar–1) and ethyl acetate (up to 1.4 L m–2 h–1 bar–1). The membrane microstructures are facilely tuned by regulating PDMS content and cross-linking time, allowing the efficient optimization of solvent resistant nanofiltration performances. Moreover, the operational stability and the separation of lotus seedpod proanthocyanidins–ethanol/water mixtures are investigated to evaluate the practical application of the composite membrane.

Bioreducible branched polyethyleneimine derivatives physically loaded with hydrophobic pheophorbide A: preparation, characterization, and light-induced cytotoxicity.

Branched-type hydrophilic polyethyleneimine derivatives (i.e., bPEI derivatives) are developed polymeric carriers for photodynamic therapy. Their chemical structures which contain pH-tunable hydrophobic/hydrophilic cavities enable efficient loading of hydrophobic drugs in basic pH environments. Intracellular stimuli trigger the release of the loaded drugs in bPEI derivatives. As expected, the hydrophobic photosensitizer known as pheophorbide A (PheoA) is solubilized by physical loading in the inner hydrophobic spaces of bPEI derivatives in environments with basic pH values. Interestingly, acidic pH environments induce aggregation, resulting in poor release of the loaded PheoA as well as in quenched photo-activity of the PheoA-loaded polymers. However, when reducible polycation derivatives of bPEI are used (i.e., RPC-bPEI), intracellular thiols degrade the disulfide linkages in the polymers, resulting in rapid PheoA release. Particularly, a RPC-bPEI containing 6 wt% PheoA (i.e., RPC-bPEI(0.8 kDa)-PheoA(6%)) respond remarkably well to light exposure and display large differences between dark toxicity and light-induced toxicity. Cellular uptake of RPC-bPEI(0.8 kDa)-PheoA(6%) is approximately sevenfold to ninefold lower than that of free PheoA. Nevertheless, the photo-toxicity of RPC-bPEI(0.8 kDa)-PheoA(6%) was only two- to sixfold less potent than that of free PheoA. These results suggest that reducible bPEI materials may act as potential solubilizers and carriers for low-molecular-weight hydrophobic anti-cancer drugs.

Dual-Responsive Polymer Micelles for Target-Cell-Specific Anticancer Drug Delivery

Efficient delivery of therapeutic agents with nanocarriers into the nucleus to achieve high therapeutic efficiency is still a major challenge for cancer therapy due to mucosal barriers, nonspecific uptake, and intracellular drug resistance. In this study, we develop a dual-responsive polymer micelle system with sheddable polyethylenimine (PEI) shells for actively targeted drug delivery. This system exhibits an ultrasensitive negative-to-positive charge reversal in response to the extracellular pH value, resulting in greatly enhanced uptake by cancer cells via electrostatic interaction. Moreover, the active targeting ability can further promote the selective uptake of the nanocarriers in the cancer cell. Once the micelles escape from the lysosomes, the disulfide linkages can be cleaved by GSH in the cytoplasm, and in turn the hydrophilic PEI shell is deshielded, leading to the rapid release of the encapsulated agent into the nuclei. The antitumor activity in 4T1 tumor-bearing mice reveals that this novel system possesses a long blood circulation due to the originally negatively charged surface and can significantly promote the cell internalization and intracellular drug release, thus leading to a high therapeutic efficacy against resistant tumors and fewer side effects to normal tissues.

Cross-linked polyacrylonitrile/polyethyleneimine–polydimethylsiloxane composite membrane for solvent resistant nanofiltration

A new approach to the facile preparation of high-performance composite membrane for solvent resistant nanofiltration is presented herein. Within the composite membrane, hydrophilic polyethyleneimine (PEI) and hydrophobic hydroxyl terminated trifluoride polydimethylsiloxane (PDMS) are cross-linked as skin layer, whereas polyacrylonitrile (PAN) ultrafilitration membrane serves as support layer. The microstructure and physicochemical properties of the membrane are extensively investigated. It is found that PEI chains and PDMS chains are covalently cross-linked via trimesoyl chloride through interfacial polymerization, generating hydrophilic–hydrophobic hybrid network. The cross-linking inhibits the chain mobility of PEI, affording the composite membrane enhanced thermal and mechanical stabilities relative to the membrane without PDMS. Combining the advantages of both hydrophilic and hydrophobic materials endows the composite membrane with excellent solvent resistance properties and nanofiltration performances in both polar solvents and nonpolar solvents, such as isopropanol, butanone, ethyl acetate, and n-heptane. Particularly, the composite membrane achieves permeate fluxes of 37.8, 3.5, 5.4, and 4.7Lm−2h−1 for these four solvents, respectively, along with the area swellings below 3.2%. After being equilibrated in these solvents, the composite membrane exhibits good structural stability with molecular weight cut-off of 600. The operation stability of the composite membrane is also explored.

Synthesis and Characterization of Highly Fluorescent Water Dispersible ZnO Quantum Dots

We report the synthesis of stable and water dispersible fluorescent zinc oxide (ZnO) quantum dots (QDs). Hydrophilic polyethyleneimine (PEI) was used to stabilize QDs in water and trisodiumcitrate was used as linker between ZnO and PEI. X-ray diffraction reveals the nanocrystalline nature and hexagonal wurtzite structure of as synthesized ZnO QDs. High-resolution transmission electron micrograph suggests nearly spherical particles of size 3-6 nm and lattice spacing of 0.28 nm corresponding to the (100) plane of zinc oxide. Water dispersed ZnO QDs exhibit efficient yellow-green fluorescence centered at 555 nm (2.23 eV) with an excitation wavelength of 360 nm, which is found to be stable for two month revealing the high stability of QDs in water.