Preparation of Thermal-responsive Chitosan-graft-N-isopropylacrylamide Membranes via γ-Ray Irradiation

A novel thermo-sensitive switching membrane has been prepared by radiation-induced simultaneous grafting N-isopropylacrylamide （NIPAAm） onto chitosan membrane. Fourier transform infrared spectroscopy （FTIR） was used to identify the structure of the grafted membranes. The surface morphology of the grafted membrane was observed from scanning electron microscopy （SEM）. Pure water flux measurements showed that water flux of the grafted membrane decreased with the increase of temperature, while that of chitosan membrane was constant. It was proved that grafted membrane was sensitive to temperature.     

Radiation-grafting of 4-vinylpyridine and N-isopropylacrylamide onto polypropylene to give novel pH and thermo-sensitive films

Here 4-vinylpyridine (4VP) was grafted onto polypropylene films (PP) by mutual irradiation method to give PP-g-4VP; N-isopropylacrylamide (NIPAAm) was then grafted onto the PP-g-4VP films to give (PP-g-4VP)-g-NIPAAm by pre-irradiation method, using a ⁶⁰Co γ-source. The dependence of grafting percentage on radiation dose, temperature, reaction time, and monomer concentration was studied. (PP-g-4VP)-g-NIPAAm films were characterized by infrared spectroscopy (FTIR-ATR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The critical pH point and lower critical solution temperature (LCST) were determined by swelling and water contact angle measurements. The LCST also was determined by DSC. The binary graft copolymer films are shown to be thermo-pH sensitive.     

PVDF Hollow fiber Membrane with High Flux and High Rejection Ratio Prepared by Irradiation Induced Grafting of PAA

Summary: A modified poly (vinylidene fluoride) (PVDF) hollow fiber membrane with higher flux and flux recovery rate was prepared by γ-radiation induced grafting of acrylic acid (AA). The influence of radiation dose and monomer concentration on the grafting degree was investigated. The results indicated that the grafting degree increased in the lower monomer volume fraction until the monomer volume fraction exceeded 20%. The grafting degree increased with the increase of radiation dose. Structural and morphological of the original and grafted membrane surface were characterized by FT-IR, scanning electron microscopy (SEM). The results indicated that acrylic acid was grafted onto PVDF hollow fiber membrane and the grafted membrane was more hydrophilic than original PVDF. There was a slight increase of breaking strength and yield stress with the increase of the grafting degree of AA. The pure water flux increased initially but decreased subsequently with the raise of grafting degree. When the grafting degree was 4.4%, the maximum pure water flux reached 1496.3 L/m² × h, 1.79 times of original membrane. The pure water flux, flux recovery rate and rejection ratio for bovine serum albumin could improve simultaneously in a low grafting degree (<4.4%).     

Gamma Radiation-Induced Graft Copolymerization of Styrene Onto Polyethyleneterephthalate Films: Application in Fuel Cell Technology as a Proton Exchange Membrane

Polyethyleneterephthalate (PET) based proton exchange membrane for using in fuel cells was successfully prepared by gamma radiation-induced graft copolymerization of styrene monomer onto PET film and the consequent selective sulfonation of the grafting chain in the film state using chlorosulfonic acid (ClSO₃H). The effects of grafting conditions (e.g., monomer concentration, irradiation dose) on the degree of grafting and sulfonation condition (e.g., optimum concentration of ClSO₃H) on the degree of sulfonation were studied. The degree of grafting, the degree of sulfonation and the physico-chemical properties (such as, water uptake, mechanical strength, thermal durability, hydrolytic stability, oxidative stability) of the gamma radiation-induced grafted membrane were found to be better when compared to those of the UV-radiation grafted membrane. The membrane shows higher ion exchange capacity (0.9 mmol g^?1) and higher proton conductivity (0.075 S cm^?1), similar to those of Nafion membrane.     

Characterization of N-isopropyl acrylamide/acrylic acid grafted polypropylene nonwoven fabric developed by radiation-induced graft polymerization

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was carried out on polypropylene nonwoven fabric to develop a thermosensitive material and has been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with different monomer ratios were characterized by thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), contact angle and atomic force microscopy (AFM). Results of FTIR clearly indicated that poly(acrylic acid) and poly(N-isopropyl acrylamide) were successfully grafted onto the membrane surface. TGA results showed that the thermal stability of PP fabric increased after grafting of NIPAAm/AA. The crystallinity values from DSC and XRD were found to decrease with increase in degree of grafting because of the addition of grafted chains within the noncrystalline region. The decrease in contact angles of the grafted fabric with an increase of the degree of grafting shows that PNIPAAm/PAA exists as the hydrophilic component. The increase in surface roughness after grafting was observed by AFM.     

Temperature-sensitive porous membrane production through radiation co-grafting of NIPAAm on/in PVDF porous membrane

N-isopropylacrylamide (NIPAAm) monomer was grafted on and in poly(vinylidene fluoride) (PVDF) micro-pore membrane by γ-irradiation. The influence of irradiation and reaction conditions on the grafting yield was investigated in detail. The chemical structure of NIPAAm-grafted PVDF (NIPAAm-g-PVDF) membrane was characterized by Fourier transform infrared spectra and X-ray photoelectron spectra measurements. The morphology of the sample surface as well as the cross-section before and after grafting was characterized by scanning electron microscope. The temperature sensitive properties of the membrane were monitored by measuring the conductance as well as the water flux through the sample thickness. The results show that the membrane exhibits clearly temperature-sensitive permeability to water as expected, i.e. the permeability of water changes dramatically as the temperature goes over the lower critical solution temperature of NIPAAm.     

Radiation grafting of N,N′-dimethylacrylamide and N-isopropylacrylamide onto polypropylene films by two-step method

Polypropylene (PP) films were modified by the consecutive grafting of N,N′-dimethylacrylamide (DMAAm) and N-isopropylacrylamide (NIPAAm) (two-step method) using preirradiation method with gamma-rays. The effect of absorbed dose, monomer concentration and reaction time on the degree of grafting was determined. The grafted samples were verified by the FTIR-ATR spectroscopy; thermal properties were analyzed by differential scanning calorimetry (DSC) and the stimuli-responsive behavior was studied by swelling and contact angle in water as well as DSC. Thermoresponsive films of (PP-g-DMAAm)-g-NIPAAm presented a lower critical solution temperature (LCST) at 36.5 °C.     

PP films grafted with N-isopropylacrylamide and N-(3-aminopropyl) methacrylamide by γ radiation: synthesis and characterization

Simultaneous grafting of N-isopropylacrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) on polypropylene (PP) was investigated for obtaining interfaces that are stimuli-responsive under physiological conditions. A pre-irradiation method was optimized tuning the γ-irradiation dose, reaction time, temperature, and monomers concentrations. FT-IR ATR and XPS analysis of the grafted copolymers evidenced a greater content in NIPAAm than in APMA; the APMA/NIPAAm ratio increasing with the concentration of APMA in the reaction medium and when the grafting was carried out in 1 M NaNO₃. The grafted films were characterized regarding their thermal properties (DSC and TGA) swelling behavior and contact angle. Immersion of the pre-irradiated films in 1 M NIPAAm/0.5 M APMA aqueous solution rendered PP-g-(1NIPAAm-r-0.5APMA) which exhibited rapid and reversible transitions showing a LCST around the physiological temperature. By contrast, a greater content in APMA enhanced the hydrophilicity and prevented the shrinking of PP-g-(1NIPAAm-r-1APMA).     

Pervaporation of ethanol-water mixtures through temperature-sensitive poly(vinyl alcohol-g-N-isopropyacrylamide) membranes

Novel temperature-sensitive membranes have been synthesized by grafting poly(N-isopropyacrylamide) (poly(NIPAAm)) onto a poly(vinyl alcohol) (PVA) backbone using hydrogen peroxide-ferrous ion as initiator. Due to the grafting of poly(NIPAAm), the hydrophilic/hydrophobic balance and the polarity of the pendent groups within the membranes are modified. Significant temperature sensitivity of the grafted membranes is observed close to the LCST of linear poly(NIPAAm) in the pervaporation processes for ethanol-water separation. Both the pervaporation and sorption selectivities for water show a maximum value in the vicinity of 30–32°C for an ethanol content of 75 and 80%. The temperature sensitivity of the grafted membranes also depends on the ethanol concentration. The maxima of pervaporation and sorption selectivities disappear when the ethanol content is lower than 75% because the much larger degree of swelling reduces the size screening effect of the membranes.     

Preparation of thermosensitive membranes by radiation grafting of acrylic acid/N-isopropyl acrylamide binary mixture on PET fabric

Thermosensitive membranes were prepared by radiation-induced graft copolymerization of monomers on PET fabrics. A binary mixture of N-isopropyl acrylamide (NIPAAm) and acrylic acid (AA) was grafted on polyester fabric as a base material to introduce thermosensitive poly(N-isopropyl acrylamide) pendant chains having LCST slightly higher than 37 °C in the membrane. The influence of ferrous sulfate, radiation dose and monomer composition on the degree of grafting was studied. The structure of the grafted fabric was characterized by thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy. The thermosensitive nature of the fabric was monitored by swelling at different temperatures. The graft copolymerization of AA with NIPAAm enhanced the LCST of the resultant membrane to ∼37 °C. The moisture vapor transmission rate (MVTR) and air permeability of the fabric decreased slightly, may be due to the slight blocking of the fabric pores. The immobilization of tetracycline hydrochloride as the model drug and its release characteristics at different temperatures were monitored.     

聚丙烯表面接枝PNIPAAm膜Ⅰ.光接枝反应和表面形态结构研究

以氧杂蒽酮或二苯甲酮为引发剂 ,通过紫外光引发表面接枝聚合的方法在聚丙烯薄膜表面引入了具有温度敏感特性的聚异丙基丙烯酰胺 (PNIPAAm)接枝聚合物层 .提高紫外光强度和接枝反应温度均有利于接枝率增大 ,而单体浓度对接枝率的影响存在最佳值 ,为 0 1 8mol L .在引发剂预浸渍引发接枝和休眠基引发接枝这两种方式中 ,后者能够实现更高的接枝率 .红外光谱 (FTIR)、X射线光电子能谱化学分析 (ESCA)和扫描电子显微镜 (SEM)等对接枝层组成的表征结果证实了接枝层的存在 .在不同温度下 ,接枝膜的FTIR谱图中酰胺I带和酰胺II带特征吸收峰发生位移 ,表明它具有温度敏感特性 .同时 ,SEM研究发现由于接枝膜的温度敏感特性而导致的球状表面形态结构     

Modification of isotactic polypropylene film by radiation-induced graft copolymerization

In the present communication we report on the radiation induced grafting of methyl methacrylate (MMA) onto irradiated isotactic polypropylene film (IPP) by Peroxidation method to prepared grafted membrane (IPP-g-MMA). The radioactive isotope ⁶⁰Co was used as the source of gamma radiation. A plausible mechanism of grafting has been proposed. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters such as radiation dose, inhibitor concentration, monomer concentration, reaction time and reaction temperature respectively. Maximum percentage of grafting (85%) was obtained at [radiation dose] = 25 kGy, [inhibitor concentration] = 0.04 wt%, [MMA] = 6 wt%, [Reaction Temperature] = 60 °C in a [Reaction time] of 120 min. The evidence of grafted membrane was characterized by Fourier transform infrared spectroscopy, Atomic force microscopy method, Scanning electron microscopy which indicates that MMA has been grafted onto IPP. Hydrolysis of the grafted membranes in 1 N NaOH transformed ester groups of the grafted membranes to carboxylic acid and hydroxyl groups to form hydrolyzed grafted membranes. Hydrolyzed grafted membranes were investigated for their swelling behavior. Swelling properties of the hydrolyzed grafted membranes were performed in different solvents such as water, N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). Maximum percentage swelling value of IPP-g-MMA was observed in pure DMSO, followed by DMF and water.     

Gas-phase and liquid-phase pre-irradiation grafting of AAc onto LDPE and HDPE films for pervaporation membranes

A study has been made on gas-phase and liquid-phase pre-irradiation grafting of acrylic acid onto LDPE and HDPE films for pervaporation membranes of ethanol-water mixtures. It was found that the degree of grafting, percent volume change of grafted membranes and length of grafting chains depend on the methods of grafting, crystal state of substrate films and diffusion rate of the monomer in the films. The pervaporation characteristics of grafted membranes is influenced directly by the surface hydrophilicity of grafted membranes, temperature of the feed, degree of grafting, crosslinking of grafted chains and alkaline metal ions in the functional groups. The potassium ion exchange membrane of HDPE synthesized by gas-phase grafting has better pervaporation efficiency. At 80 wt% ethanol in the feed, 25°C feed temperature and 70% degree of grafting a grafted membrane has a 0.65 kg/m²h flux and a separation factor of 20.     

Radiation grafting of pH and thermosensitive N-isopropylacrylamide and acrylic acid onto PTFE films by two-steps process

Polytetrafluoroethylene (PTFE) was grafted (g) with acrylic acid (AAc) by γ-ray pre-irradiation method to get PTFE-g-AAc films, then N-isopropylacrylamide (NIPAAm) was grafted onto PTFE-g-AAc films with γ-ray to get (PTFE-g-AAc)-g-NIPAAm. PTFE films were irradiated in air at a dose rate of 3.0 kGy h^–1 and different radiation dose. The irradiated films were placed in glass ampoules, which contained aqueous solutions with different monomer concentration (AAc), and then they were heated at different temperatures and reaction time. NIPAAm onto PTFE-g-AAc was carried out with the same procedure with monomer concentration of 1 mol L⁻¹. The thermosensitivity of the samples was defined and calculated as the ratio of the grafted samples swelling at 28 and 35 °C, and pH sensitivity defined as the ratio of the grafted samples swelling at pH 2 and 8.     

Surface modification of lyocell fibres by graft copolymerization of thermo-sensitive poly-N-isopropylacrylamide

Thermo-sensitive poly-N-isopropylacrylamide (poly-NIPAAm) was grafted onto lyocell fibres using cerium ammonium nitrate (CAN) as initiator. The effects of initiation time, initiator concentration, monomer concentration and grafting time on the degree of grafting were investigated. A 15-60 min exposure time, 7.5 mM CAN solution concentration and a 0.5-1 mM NIPAAm monomer concentration were optimal for obtaining a maximum degree of grafting (60-70% at 24 h grafting time) of poly-NIPAAm on lyocell fibres. Higher degree of grafting was obtained increasing the grafting time, such as 120% at 72 h.The properties of the obtained poly-NIPAAm/lyocell copolymer were also investigated. Specifically, the effects of temperature and degree of grafting of poly-NIPAAm on the swelling behaviour of the copolymer were experimentally determined. Moreover, structural characterization, thermal behaviour and morphology of the poly-NIPAAm/lyocell copolymers were examined by Fourier Transform Infrared Spectroscopy (FTIR), Differencial Scanning Calorimetry (DSC) and Scanning electron microscopy (SEM) techniques, respectively.     

Stimuli-responsive membranes through peroxidation radiation-induced grafting of 2-hydroxyethyl methacrylate (2-HEMA) onto isotactic polypropylene film (IPP)

Stimuli-responsive membranes were prepared by peroxidation radiation-induced grafting of 2-hydroxyethyl methacrylate (2-HEMA) onto IPP. The radioactive isotope ⁶⁰Co was used as the source of gamma radiation. A plausible mechanism of grafting has been proposed. Using this method, the degree of grafting and morphology could be controlled through the variation of reaction parameters such as total dose, inhibitor concentration, monomer concentration, reaction time, reaction temperature and solvents. Maximum percentage of grafting (210?%) was obtained at total radiation dose of 20?kGy. The graft copolymerization reaction was carried out for 3?h with 20?v/v% of the monomer (2-HEMA) in methanol at 85?°C using 0.06?wt% of FeCl₃ as inhibitor. The chemical structures of grafted membranes were characterized by Fourier transform infrared spectroscopy (FTIR) which indicates that HEMA has been grafted onto IPP. The atomic force microscopy (AFM), scanning electron microscopy (SEM) techniques were used to assess the morphological characterization of the membranes, revealing the roughness of the surface. These membranes were investigated for their swelling behavior. pH-sensitivity and the dyeability of the grafted and ungrafted membranes have also been studied.     

苯乙烯/马来酸酐和苯乙烯/甲基丙烯酸二甲氨基乙酯二元体系在聚四氟乙烯多孔膜上的γ辐射接枝

在氮气的氛围下用γ辐照的方法在聚四氟乙烯多孔膜上接枝苯乙烯 马来酸酐、苯乙烯 甲基丙烯酸二甲氨基乙酯二元单体 .并且研究了剂量、剂量率、溶液中单体的浓度和二元单体的摩尔比等条件对接枝率的影响 .探讨了两种单体的竞聚率对接枝率、接枝膜的组成及性能的影响 .结果表明 ,苯乙烯 马来酸酐二元体系对接枝率有协同效应 ,苯乙烯 甲基丙烯酸二甲氨基乙脂二元体系对接枝率表现为加合效应 .制备的二元接枝的聚四氟乙烯多孔膜可以进一步磺化来制备用于质子交换膜燃料电池的质子交换膜 .     

Microfluidic chip with thermoresponsive boronate affinity for the capture–release of cis‐diol biomolecules

The polydimethylsiloxane microfluidic chip grafted with poly(N‐isopropylacrylamide‐3‐acrylamidephenylboronic acid) (P(NIPAAm‐co‐AAPBA)) was fabricated by UV‐induced grafting polymerization for the capture–release of cis‐diol‐containing biomolecules by temperature‐modulated changes instead of changing the pH value of the mobile phase. Based on the optimal time for benzophenone soaking and UV irradiation of grafting polymerization, P(NIPAAm‐co‐AAPBA) was successfully grafted on the polydimethylsiloxane substrates, which were characterized by scanning electron microscopy, water contact angle measurements, and Fourier transform infrared spectroscopy. The P(NIPAAm‐co‐AAPBA)‐grafted polydimethylsiloxane microfluidic chip can be successfully used for the capture and release of cis‐diol‐containing adenosine by adjusting the temperature from 4 to 55°C, and the result was validated by Triple Quad liquid chromatography with mass spectrometry. With further development, the fabricated polydimethylsiloxane microfluidic chips might be chosen as a potential tool for the capture and release of cis‐diol‐containing macromolecules, such as horseradish peroxidase and glycoprotein.     

Radiation-induced grafting of styrene onto ultra-high molecular weight polyethylene powder and subsequent film fabrication for application as polymer electrolyte membranes: I. Influence of grafting conditions

Ultra-high molecular weight polyethylene (UHMWPE) powder was irradiated by gamma rays using a ⁶⁰Co source. Simultaneous and pre-irradiation grafting was performed in air and in inert atmosphere at room temperature. The monomer selected for grafting was styrene, since the styrene-grafted UHMWPE could be readily post-sulfonated to afford proton exchange membranes (PEMs). The effect of absorbed radiation dose and monomer concentration in methanol on the degree of grafting (DG) is discussed. It was found that the DG increases linearly with increase in the absorbed dose, grafting time and monomer concentration, reaching a maximum at a certain level. The order of rate dependence of grafting on monomer concentration was found to be 2.32. Furthermore, the apparent activation energy, calculated by plotting the Arrhenius curve, was 11.5 kJ/mole. Lower activation energy and high rate dependence on monomer concentration shows the facilitation of grafting onto powder substrate compared with film. The particle size of UHMWPE powder was measured before and after grafting and found to increase linearly with increase in level of grafting. FTIR-ATR analysis confirmed the styrene grafting. The grafted UHMWPE powder was then fabricated into film and post-sulfonated using chlorosulfonic acid for the purposes of evaluating the products as inexpensive PEM materials for fuel cells. The relationship of DG with degree of substitution (DS) of styrene per UHMWPE repeat unit and ion exchange capacity (IEC) is also presented.     

Relations entre la structure et les proprietes des membranes de polytetrafluoroethylene greffe—I. Membranes monogreffees carboxyliques ou basiques

We have determined the equilibrium properties (neutralization and swelling and the transport properties: conductivity and dialysis) of hydrophilic membranes obtained by radiation grafting of acrylic acid or 4-vinylpyridine onto thin PTFE films. The presence of strong counter-ion-membrane interaction (PTFE-PAA-K⁺ and PTFE-P4VP-ClO^?₄) has been confirmed in the beginning of neutralization. The grafting ratios of the samples ranged between a few percent and several hundreds percent. The properties have been studied in connection with the average degrees of ionization and the average molalities of the reactive groups throughout the whole thickness of the membrane. The parameters of the synthesis which determine the structure of acid or basic grafted chains also have an influence on the properties of the resulting membranes. For a high dose-rate (> 100 rad min^?1), the properties of carboxylic membranes are related to the degree of cross-linking: for smaller dose rates, the properties are related to the length of the grafted branches and/or to the state of the skeleton of PTFE. For the basic membranes, the properties are controlled by the length of the grafted branches and the importance of the micro-phase-separation between PTFE and the grafted chains; for low dose rates, when the grafted branches are long, separation of hydrophobic and ionizable zones is noticed for grafting ratios higher than 5%. The carboxylic membranes with lower degrees of grafting, prepared with a high dose rate, exhibit very good permselectivity. The pyridinic membranes with a low degree of grafting could be of practical interest, viz. the manufacture of selective electrodes for perchlorate ions.