Binding properties of polyamidoamine dendrimers

Dendrimers are globular, hyperbranched polymers possessing a high concentration of surface functional groups and internal cavities. These unique features make them good host molecules for small ligands. To reveal relationships between dendrimer size and its encapsulating properties, the interactions of the fourth and the sixth generations of polyamidoamine dendrimers (PAMAM G4 and PAMAM G6) with a fluorescent dye 1‐anilinonaphthalene‐8‐sulfonate (ANS) were studied. Because ANS is a fluorescent molecule and its fluorescence is very sensitive to changes in its microenvironment, it was possible to use spectrofluorometric methods to evaluate the interactions with dendrimers. A double fluorometric titration method was used to estimate a binding constant and the number of binding centers. There were two types of dendrimer binding centers characterized by different affinity towards ANS. For PAMAM G4, the values of K_b and n for low‐affinity and high‐affinity sites equaled to 2.6 × 10⁵, 0.60 and 3.70 × 10⁶, 0.34, respectively, whereas in the case of PAMAM G6, these values equaled to 1.2 × 10⁵, 76.34 and 1.38 × 10⁶, 22.73. It was observed that the size of the dendrimer had a strong impact on the number of ANS molecules that interacted with dendrimers and their location within the macromolecule. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2036–2040, 2007     

High‐performance PDMS membranes for pervaporative removal of VOCs from water: The role of alkyl grafting

To improve the pervaporation performance of PDMS membrane, alkyl groups with different chain length were grafted into PDMS matrix. The prepared membranes were characterized by ATR‐IR, DSC, TGA, PALS, and tensile testing. The effects of alkyl grafting on pervaporation performance of PDMS membrane were investigated in separation of ethyl acetate/water mixture. Experimental results show that the separation factor of PDMS membrane is largely improved by alkyl grafting because of the enhanced preferential sorption of ethyl acetate, and this improvement depends on alkyl grafting ratio and alkyl chain length. The total flux of PDMS membrane reduces after alkyl grafting owing to the decreased free volume. When grafting ratio is above 6.9%, membrane grafted with shorter alkyl groups is preferred for pervaporation. The best pervaporation performance is achieved by 9% octyl grafted PDMS membranes with a separation factor of 592 and a total flux of 188 gm^?2 h^?1 in separation of 1% ethyl acetate/water mixture at 40 °C. Moreover, this octyl grafted PDMS membrane also exhibits excellent separation performance in removal of butyl acetate, methyl‐tert‐butyl ether, and n‐butanol from water. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43700.     

A study of antimicrobial property of textile fabric treated with modified dendrimers

Dendrimers have been used as a vehicle to develop the antimicrobial properties of textile fabrics. We have taken advantage of the large number of functional groups present in the regular and highly branched three‐dimensional architecture of dendrimers. In this study, the poly(amidoamine) (PAMAM) G‐3 dendrimer was modified to provide antimicrobial properties. Following a procedure similar to what is suggested in the literature, PAMAM (G3) with primary amine end groups was converted into ammonium functionalities. The modification was then confirmed by FTIR and ¹³C‐NMR analysis. Dendrimers have unique properties owing to their globular shape and tunable cavities, this allows them to form complexes with a variety of ions and compounds; and also act as a template to fabricate metal nanoparticles. AgNO₃–PAMAM (G3) complex as well as a MesoSilver–PAMAM (G3) complex were formed and these modified dendrimers were characterized by a UV–Visible spectrophotometer to study the complex formation. Modified dendrimers were applied to the Cotton/Nylon blend fabric. SEM and EDX analysis were performed to study the dispersion of silver nanoparticles onto the fabric. An antimicrobial test of the treated‐fabric against Staphylococcus aureus exhibited significant biocidal activities for each type of modified‐dendrimer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Grafting of N‐carbamyl maleamic acid onto a styrene–butadiene–styrene copolymer

A styrene–butadiene–styrene block copolymer (SBS) was functionalized with N‐carbamyl maleamic acid (NCMA) using two peroxide initiators with the aim of grafting polar groups onto the molecular chains of the polymer. The influence of the concentration of benzoyl peroxide (BPO) and 2,5‐dimethyl, 2,5‐diterbuthylperoxihexane (DBPH) was studied. The concentration of peroxy groups ranged between 0.75 and 6 × 10^?4 mol % while the concentration of NCMA was constant at 1 wt %. The reaction temperature was chosen according to the type of peroxide employed, being 140°C for BPO and 190°C for DBPH. FTIR spectra confirmed that NCMA was grafted onto the SBS macromolecules. It was found that the highest grafting level was achieved at a concentration of peroxy groups of about 3 × 10^?4 mol %. Contact angle measurements were used to characterize the surface of the SBS and modified polymers. The contact angle of water drops decreased with the amount of NCMA grafted from 95°, the one corresponding to the SBS, to about 73°. T‐peel strength of polymer/polyurethane adhesive/polymer joints made with the modified polymers was larger than those prepared with the original SBS. The peel strength of SBS modified with 1.5 and 3 × 10^?4 mol % of peroxy groups from BPO were five times larger than that of the original SBS. The materials modified using BPO showed peel strengths higher than the ones obtained with DBPH. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4468–4477, 2006     

The effect of side chains on the reactive rate and surface wettability of pentablock copolymers by ATRP

The reactive rate and surface wettability of three pentablock copolymers PDMS‐b‐(PMMA‐b‐PR)₂ (R = 3FMA, 12FMA, and MPS) obtained via ATRP for coatings are discussed. Poly(dimethylsiloxane) (PDMS) is used as difunctional macroinitiator, poly(methyl methacrylate) (PMMA) as the middle block, while poly(trifluoroethyl methacrylate) (P3FMA), poly(dodecafluoroheptyl methacrylate) (P12FMA) and poly(3‐(trimethoxysilyl)propyl methacrylate) (PMPS) as the end block, respectively. Their reactive rates obtained by gas chromatography (GC) analysis indicate that 3FMA gains 8.053 × 10^?5 s^?1 reactive rate and 75% conversion, higher than 12FMA (4.417 × 10^?5 s^?1, 35%), but MPS has 1.9389 × 10^?4 s^?1 reactive rate and 96% conversion. The wettability of pentablock copolymer films is characterized by water contact angles (WCA) and hexadecane contact angles (HCA). The PDMS‐b‐(PMMA‐b‐P12FMA)₂ film behaves much higher advancing and receding WAC (120° and 116°) and HCA (60° and 56°) than PDMS‐b‐(PMMA‐b‐P3FMA)₂ film (110° and 106° for WAC, 38° and 32° for HAC) because of its fluorine‐rich surface (20.9 wt % F). However, PDMS‐b‐(PMMA‐b‐PMPS)₂ film obtains 8° hysteretic contact angle in WAC (114°–106°) and HAC (32°–24°) due to its higher surface roughness (138 nm). Therefore, the fluorine‐rich and higher roughness surface could produce the lower water and oil wettability, but silicon‐rich surface will produce lower water wettability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40209.     

Novel PDMS‐based membranes: Sodium chloride and glucose permeability

Permeation of sodium chloride and glucose through polydimethylsiloxane‐poly(N‐isopropylacrylamide) (PDMS‐PNIPAAm) interpenetrating polymer networks (IPNs) of two different microstructures was investigated. We have successfully developed small‐molecule permeable IPNs, by modifying PDMS film structure. A group of PDMS films was prepared using conventional solvent casting (SC) method and another group produced by introducing oil, followed by SC and leaching the oil out (SCOL method). Scanning electron microscopy (SEM) and attenuated total reflection fourier transformer infrared (ATR‐FTIR) spectroscopy results confirmed the presence of PNIPAAm in the SC and SCOL IPNs. Results obtained from spectra of differential scanning calorimetry (DSC) showed that these IPNs had a phase transition temperature at about 32°C. Permeation measurements showed that the presence of PNIPAAm as the second phase in the IPN, improved the permeability of PDMS film. According to the results, maximum permeation coefficient was related to SCOL IPN containing 15.8% ± 0.3%PNIPAAm, at 23°C (5.98 × 10^?7 ± 7.93 × 10^?9 cm²/s for sodium chloride and 3.6 × 10^?7 ± 7 × 10^?9 cm²/s for glucose). These results suggested that these PDMS‐PNIPAAm IPNs with sodium chloride and glucose permeability may be further developed as ophthalmic biomaterials or corneal replacements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and characterization of transparent and foldable polysiloxane‐poly(methyl methacrylate) membrane with a high refractive index

In this article, carbazole‐grafted methacrylic polysiloxane (MA‐CZ‐PDMS) macromonomer was synthesized and its structure was confirmed by proton nuclear magnetic resonance (¹H NMR). The polysiloxane macromonomer can homogeneously copolymerize with methyl methacrylate (MMA) to prepare transparent and foldable carbazole‐grafted polysiloxane‐poly(methyl methacrylate) (PDMS‐PMMA) membranes with a high refractive index (RI). The membranes were characterized by light transmittance, RI value, and dynamic mechanical thermal analysis (DMTA). The results indicated that the carbazole‐grafted PDMS‐PMMA membranes had excellent light transmittance that decreased slightly with increasing carbazole‐grafted polysiloxane content. Incorporation of carbazole‐grafted polysiloxane in the materials improved its RI value; however decreased the glass transmission temperature (T_g) that can be adjusted to less than 30°C, enable the membrane foldable at room temperature. The data demonstrate that the carbazole‐grafted PDMS‐PMMA membranes have a potential application as high RI intraocular lens (IOL) suitable for implantation by minimally invasive surgery. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42491.     

Plasma‐induced grafting of hydroxyethyl methacrylate (HEMA) onto chitosan membranes by a swelling method

Hydroxyethyl methacrylate (HEMA) was grafted onto chitosan membranes by plasma‐graft polymerization. Effects of monomer concentration, plasma power and plasma time on the amount of grafting were investigated. The results showed that there were two processes: grafting polymerization and etching of the membrane. The surface of the grafted membrane was evaluated by FTIR. Scanning electron microscopy indicated that the surface morphology of the grafted membrane could be adjusted through plasma power. Water contact angles of the chitosan surface decreased from 78.2° to 45.4° while the amount of grafting increased from 0 to 12.2%, indicating improved hydrophilicity of the membrane surface. Permeation coefficients through the original membrane, the membrane treated at 55 W for 15 min, and the membrane treated at 55 W for 30 min for creatinine were 9.12 × 10^?7, 10.6 × 10^?7 and 8.57 × 10^?7 cm² s^?1, respectively. Thermogravimetry and mechanical testing showed that there were no significant changes on the bulk property of chitosan membrane after modification. © 2003 Society of Chemical Industry     

Gel permeation chromatography of poly(dimethyl siloxane). I. The universal calibration

The Benoit universal calibration method has been tested for evaluation of GPC data of polydimethylsiloxane (PDMS) in toluene at 60°C. For the conversion of the calibration curve for polystyrene to the PDMS calibration curve, the Mark–Houwink equation for PDMS in toluene at 60°C was derived: [η] = 9.77 × 10^?5 M^0.725. The applicability of this universal calibration was proved by the experimental results on five PDMS model samples. For the correct evaluation of the PDMS elution curve, the use of the true calibration is inevitable, because the hydrodynamic volume of PDMS molecular weight unit is somewhat different from the polystyrene one.     

Retention and reusability of trypsin activity by covalent immobilization onto grafted polyethylene plates

This study investigated the activity of trypsin that had been covalently immobilized onto acrylic acid (AA)– and methacrylic acid (MAA)–grafted polyethylene (PE) plates—PE–g–PAA and PE–g–PMAA—using a water‐soluble carbodiimide as a coupling agent, as a function of the immobilized amount, the grafted amount, the pH value on immobilization, and the pH value and temperature at the activity measurement. The activity of trypsin immobilized on the PE–g–PAA plates at pH 6.0 decreased with an increase in the immobilized amount because of the crowding of trypsin molecules in the vicinity of the surfaces of the grafted PAA layers. The increase in the grafted amount resulted in a decrease in the activity of immobilized trypsin because of a decrease in the diffusivity of BANA molecules caused by the formation of dense grafted PAA layers for the PE–g–PAA plates and led to the increased activity because of the increase in the hydrophilicity of the whole grafted layers for the PE–g–PMAA plates. The activity of trypsin immobilized on the PE–g–PAA and PE–g–PMAA plates at pH 6 increased with an increase in the pH value, probably because of the expansion of trypsin‐carrying grafted PAA and PMAA chains and the increased diffusivity of Nα‐benzoyl‐DL ‐arginine‐nitroanilide hydrochloride molecules in the grafted layers. The optimum temperature of the activity of immobilized trypsin shifted to 50°C from 30°C for native trypsin. Immobilized trypsin was reusable without any denaturation and isolation at temperatures ranging from 20°C to 60°C and pH values ranging from 6 to 10. Trypsin immobilized on a PE–g–PAA plate had 95% of the remaining activity in relation to native trypsin at 30°C after preservation in a pH 7.8 buffer at 4°C over 6 months. These results made clear that alkaline and thermal stability, reusability, and storage stability can be much improved by the covalent coupling of trypsin on PE–g–PAA and PE–g–PMAA plates. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3574–3581, 2003     

Application of recycled polyol and benzimidazole to the enhancement of antifungal activity of polyurethane

Recycled polyol and benzimidazole were both grafted onto polyurethane (PU) to enhance the surface hydrophilicity and antifungal activity, respectively. The two grafted groups affected the viscosity, crosslink density, soft segment glass transition, breaking stress, flexibility at freezing temperature, shape recovery at ?10 °C, surface hydrophilicity, and antifungal activity. The glass transition temperature increased from ?67.5 °C for plain PU up to ?60.8 °C after the grafting of polyol. The breaking stress and shape recovery of the grafted PU increased up to 425% and 200%, respectively, relative to plain PU because of the chemical linking by the grafted polyol. The hydrophilicity of PU, evaluated by the water contact angle and water swelling ratio, increased with increasing polyol content. A PU sample demonstrated excellent low‐temperature flexibility in comparison to plain PU and control sample. Finally, the PUs modified with grafted polyol and benzimidazole completely suppressed fungal growth. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46600.     

Poly(L‐lactide). X. Enhanced surface hydrophilicity and chain‐scission mechanisms of poly(L‐lactide) film in enzymatic,alkaline, and phosphate‐buffered solutions

Attempts were carried out to enhance the surface hydrophilicity of poly(L ‐lactide), that is, poly(L ‐lactic acid) (PLLA) film, utilizing enzymatic, alkaline, and autocatalytic hydrolyses in a proteinase K/Tris–HCL buffered solution system (37°C), in a 0.01N NaOH solution (37°C), and in a phosphate‐buffered solution (100°C), respectively. Moreover, its chain‐scission mechanisms in these different media were studied. The advancing contact‐angle (θ_a) value of the amorphous‐made PLLA film decreased monotonically with the hydrolysis time from 100° to 75° and 80° without a significant molecular weight decrease, when enzymatic and alkaline hydrolyses were continued for 60 min and 8 h, respectively. In contrast, a negligible change in the θ_a value was observed for the PLLA films even after the autocatalytic hydrolysis was continured for 16 h, when their bulk M_n decreased from 1.2 × 10⁵ to 2.2 × 10⁴ g mol^?1 or the number of hydrophilic terminal groups per unit weight increased from 1.7 × 10^?5 to 9.1 × 10^?5 mol g^?1. These findings, together with the result of gravimetry, revealed that the enzymatic and alkaline hydrolyses are powerful enough to enhance the practical surface hydrophilicity of the PLLA films because of their surface‐erosion mechanisms and that its practical surface hydrophilicity is controllable by varying the hydrolysis time. Moreover, autocatalytic hydrolysis is inappropriate to enhance the surface hydrophilicity, because of its bulk‐erosion mechanism. Alkaline hydrolysis is the best to enhance the hydrophilicity of the PLLA films without hydrolysis of the film cores, while the enzymatic hydrolysis is appropriate and inappropriate to enhance the surface hydrophilicity of bulky and thin PLLA materials, respectively, because a significant weight loss occurs before saturation of θ_a value. The changes in the weight loss and θ_a values during hydrolysis showed that exo chain scission as well as endo chain scission occurs in the presence of proteinase K, while in the alkaline and phosphate‐buffered solutions, hydrolysis proceeds via endo chain scission. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1628–1633, 2003     

Selective determination of dopamine in the presence of ascorbic acid using ferrocenyl-tethered PAMAM dendrimers modified glassy carbon electrode

Determination of dopamine (DA) in the absence and presence of ascorbic acid (AA) by ferrocenyl-tethered PAMAM G3 dendrimers (Fc-D) modified glassy carbon electrode (GCE) was reported. The modified electrode was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Factors influencing the detection processes were optimized and kinetic parameters were calculated. The sensor exhibited excellent catalytic activities for the oxidation–reduction reactions of DA and eliminated the interference of AA. Under optimal condition, the linear range of 1 × 10⁻⁵–1.5 × 10⁻³ mol L⁻¹ and the detection limit of 4.7 × 10⁻⁶ mol L⁻¹ was obtained. This study provides a new idea for the determination of DA in the presence of AA.     

Grafting of methyl methacrylate (MMA) onto Antheraea assama silk fiber

Graft copolymerization of methyl methacrylate (MMA) onto nonmulberry silk fiber Antheraea assama was investigated in aqueous medium using the KMnO₄–oxalic acid redox system. Grafting (%) was determined as a function of the reaction time, temperature, and monomer and initiator concentrations. The rate of grafting increased progressively with increase of the reaction time up to 4 h and then decreased. The extent of grafting was maximum at 55°C. The extent was also dependent upon monomer and initiator concentrations up to 75.5 × 10^?2 and 6 × 10^?3 M, respectively. The grafted products were evaluated by infrared spectroscopy and their thermal decompositions were studied by TG and DTG techniques in static air at 20°C min^?1 and 30°C min^?1 in the range 30–800°C. The kinetic parameters for ungrafted and grafted fibers were evaluated using the Coats and Redfern method. The grafted products were found to be thermally more stable than were those of the ungrafted fibers. The surface characteristics of the ungrafted and grafted fibers were evaluated by scanning electron microscopy. The water‐retention values (WRVs) of the grafted fibers were in decreasing order with increase in the grafting (%). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2633–2641, 2001     

Rhodium Complexed C2‐PAMAM Dendrimers Supported on Large Pore Davisil Silica as Catalysts for the Hydroformylation of Olefins

Polyamidoamine (PAMAM) dendrimers up to the third generation were grown for the first time on the surface of a large‐pore (18 nm) Davisil silica support. The supported dendrimers of generations 0, 1, 2 and 3 were phosphinomethylated and complexed with rhodium. All the generations were found to be very active for the hydroformylation of olefins. The hydroformylation of 1‐octene was accomplished with a turnover frequency of 1700 h⁻¹ at 70 °C. The G(1) material was found to be the most active when the different generations were compared at 50% conversion at 70 °C     

Chemically functionalized graphene/polymer nanocomposites as light heating platform

Chemically functionalized graphene (CFG) is proposed as a novel nanoscale optical heater by uniformly dispersing it in poly(dimethylsiloxane) (PDMS) matrix. And subsequently, a simple, fast, and localized heating method on microfluidic chips is demonstrated. CFG is prepared through simultaneous modification and reduction of graphene oxide with dodecylamine by a solvothermal route. It is well dispersed in PDMS suspension to form uniform CFG/PDMS composite due to the presence of the long‐dodecyl chain. The obtained CFG/PDMS composites are readily made into microfluidic chips by standard soft lithography. The localized optical heating on the chip is realized by employing a conventional semiconductor laser as light source. The prepared chips with low to 0.05 wt% CFG contents can exhibit temperature increase (<1 min) at very low power illumination. The optical heating effects were observed not only under irradiation with long wavelength, but also under the wavelengths as short as 405 nm. Our studies illustrated that CFG/PDMS composite can serve as a practical optical heating platform for microfluidic chips with the advantages of simple, low cost, and high efficiency. POLYM. COMPOS., 37:1350–1358, 2016. © 2014 Society of Plastics Engineers     

Graft copolymerization of N-isopropylacrylamide on styrene-butadiene-styrene block copolymer

Graft polymerization of N-isopropylacrylamide (NIPAAm) onto styrene-butadiene-styrene (SBS) block copolymer using benzoyl peroxide was studied to improve the water absorptivity and thermosensitivity of SBS. The influence of various grafting reaction factors on the conversion of NIPAAm and the grafting percentage of SBS-g-NIPAAm were also investigated in the study. The experimental results showed that the conversion of SBS-g-NIPAAm was enhanced as the monomers of NIPAAm were increased. The maximum conversion of SBS-g-NIPAAm was observed when the molar ratio of NIPAAm to butadiene was 1.25. In addition, increasing the reaction time enhanced the conversion of SBS-g-NIPAAm; the maximum grafting percentage was obtained with a 4-h reaction. The optimal concentration of the initiator was 3 × 10⁻⁴ mol/20 mL of toluene, and the grafting reaction occurred at over 65°C. The test results of the hydrophilicity of the grafted membranes showed that the hydrophilicity and thermosensitivity were significantly enhanced by grafting NIPAAm onto SBS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2641–2650, 2001     

Biopolymer brushes grown on PDMS contact lenses by in situ atmospheric plasma-induced polymerization

It is critical for silicone based-contact lens development by improving surface characterization to prevent protein adsorption. In this paper, the silicone (polydimethylsiloxane, PDMS) contact lenses were modified by varied molecular weights of poly(ethylene glycol) methacrylate (PEGMA, Mw 360 and 500 Da) polymer brushes by in situ atmospheric plasma-induced surface copolymerization. After PDMS contact lenses were homogenously immersed in PEGMA monomer solutions, varied gases (oxygen, nitrogen, and argon) with the atmospheric plasma were employed in the process of polymerization. The characterizations of PEGMA polymer brushes modified on the PDMS contact lenses would be evaluated by atomic force microscopy, FT-IR spectroscopy, X-ray photoelectron spectroscopy, and contact angle test. The results show that the hydrophilicity of the PEGMA polymer brush-modified surface is obviously improved. The contact angle of PEGMA-modified surface decreases about 20°–40° by varied atmospheric plasma (O₂, N₂, and Ar gases), compared to the pristine lenses. Importantly, the hydrophilicity of the PEGMA polymer brush-modified surface could be retained beyond 2 weeks. PEGMA-modified PDMS contact lenses also display superior anti-protein (fibrinogen and human serum bovine) adsorption ability. Therefore, immobilization of PEGMA polymer brushes by in situ atmospheric plasma-induced polymerization would be a great and rapid method to enhance the hydrophilicity and anti-protein adsorption ability in the PDMS contact lenses.     

Preparation of well-dispersed and anti-oxidized Ni nanoparticles using polyamioloamine dendrimers as templates and their catalytic activity in the hydrogenation of <Emphasis Type="Italic">p</Emphasis>-nitrophenol to <Emphasis Type="Italic">p</Emphasis>-aminophenol

p-Aminophenol was synthesized by catalytic hydrogenation of p-nitrophenol on Ni nanoparticles prepared by a chemical reduction method using polyamidoamine (PAMAM) dendrimers as templates. The as-prepared Ni nanoparticles were characterized by XRD, LRS, EDS, FTIR, FESEM, HRTEM and N₂ sorption analysis. Smaller-sized, better-dispersed and more active Ni nanoparticles can be successfully achieved using PAMAM dendrimers as templates. Analysis results show the as-prepared Ni nanoparticles are pure f.c.c. nickel. In hydrogenation reactions of p-nitrophenol, Ni nanoparticles show higher catalytic activity than that of Ni nanoparticles prepared in the absence of PAMAM dendrimers. The weight ratio of PAMAM/Ni²⁺ is proved to be an important parameter on the catalytic activity of Ni nanoparticles and the optimal ratio is 15%. The reason proposed for higher catalytic activity of Ni nanoparticles is a combination effect of smaller particle size, better dispersion and more active Ni nanoparticles.     

ZIF-8 Filled Polydimethylsiloxane Membranes for Pervaporative Separation of n-Butanol from Aqueous Solution

ZIF-8-filled polydimethylsiloxane (PDMS) membranes, PDMS/ZIF-8, were prepared by a two-step polymerization process and were used to recover n-butanol from an aqueous solution by pervaporation (PV). Compared with pure PDMS membrane, PDMS/ZIF-8 membranes demonstrated an obviously higher n-butanol permselectivity. As an increase of ZIF-8 content, n-butanol/water selectivity increased initially and then decreased, while the n-butanol and water permeability decreased monotonously. PDMS/ZIF-8 membrane containing 2 wt% ZIF-8, that is, PDMS/ZIF-8-2 showed the highest selectivity. On the other hand, selectivity and permeability for n-butanol and water of PDMS/ZIF-8-2 membrane decreased with the increase of operating temperature. The selectivity and permeability for n-butanol reached 7.1 and 3.28 × 10⁵ barrer, respectively, at 30°C when the feed concentration of n-butanol was 0.96 wt%.