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1.
Poly(N‐vinyl 2‐pyrrolidone‐g‐citric acid) (PVP‐g‐CA) hydrogels with varying compositions were prepared from ternary mixtures of N‐vinyl 2‐pyrrolidone–citric acid–water by using 60Co γ‐rays. The effect of gel composition on the uranyl ions adsorption capacity of PVP‐g‐CA hydrogels was investigated. Uranyl adsorption capacity of these hydrogels were found to be in the range of 18–144 mg [UO]/g dry gel from the aqueous solution of uranyl nitrate and 22–156 mg [UO]/g dry gel from the aqueous solution of uranyl acetate, depending on the content of citric acid in the hydrogel, while poly(N‐vinyl 2‐pyrrolidone) hydrogel did not sorb any uranyl ion. The swelling of PVP‐g‐CA hydrogel containing 2.7 mol % CA was observed in water (1620%), in uranyl acetate solution (1450%) and in uranyl nitrate solution (1360%), as compared to 700% swelling of pure PVP hydrogels. The diffusion coefficients were varied from 12.57 up to 4.04 • 10−8 m2 s−1. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1037–1043, 2000  相似文献   

2.
Poly‐electrolyte N‐vinyl 2‐pyrrolidone‐g‐tartaric acid (PVP‐g‐TA) hydrogels with varying compositions were prepared in the form of rods from ternary mixtures of N‐vinyl 2‐pyrrolidone/tartaric acid/water. The effect of external stimuli, such as the solution pH, ionic strength, and temperature, on uranyl adsorption by these hydrogels was investigated. Uranyl adsorption capacities of the hydrogels were determined to be 53.2–72.2 (mg UO/g dry gel) at pH 1.8, and 35.3–60.7 (mg UO/g dry gel) at pH 3.8, depending on the amount of TA in the hydrogel. The adsorption studies have shown that the temperature and the ionic strength of the swelling solution also influence uranyl ion adsorption by PVP‐g‐TA hydrogels. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2219–2226, 2000  相似文献   

3.
A complex of poly-4-vinylpyridine with iodine is formed when a thin film of the polymer is immersed in a I/I redox couple solution. A hydroxyaluminum phthalocyanine photoelectrochemical cell presents short-circuit current up to 107.3 μA cm−2 for a conversion efficiency of 0.035% when the organic film is coated with the polymer layer in an iodine/iodide electrolyte. This improvement is assigned to the contribution of the complex itself and to the decrease in the series resistance of the cell.  相似文献   

4.
Thermally‐induced self‐crosslinking behaviour has been found in copolymers containing N‐methyl‐N‐vinylbenzylpyrrolidinium chloride (MVBPC) and methyl methacrylate (MMA). NMR, IR and low molecular weight model reactions demonstrate that this crosslinking reaction occurs between the methyl ester groups of the MMA units and the quaternary ammonium salts, with the resulting benzyl esters forming chemical links between the MVBPC and MMA units with the formation of N,N‐dimethylpyrrolidinium chloride. Similar crosslinking behaviour has also been found when the Cl anion is replaced by Br and I, but not in the case of BF as counter anion. © 2000 Society of Chemical Industry  相似文献   

5.
Surface activity and micellar behavior in aqueous media in the temperature range 20–50°C of the two block copolymers, Me2N(CH2)2OE39B18, (DE40B18) and I?Me3N+(CH2)2OE39B18, (TE40B18) in the premicellar and postmicellar regions have been studied by surface tensiometry, viscometry, and densitometry. Where E represents an oxyethylene unit while B an oxybutylene unit. Various fundamental parameters such as, surface excess concentrations (Γm), area per molecule (a) at air/water interface and standard Gibbs free energy for adsorption, ΔG have been investigated for the premicellar region at several temperatures. The thermodynamic parameters of micellization such as, critical micelle concentrations, CMC, enthalpy of micellization, ΔH, standard free energy of micellization ΔG, and entropy of micellization ΔS have also been calculated from surface tension measurements. Dilute solution viscosities have been used to estimate the intrinsic viscosities, solute‐solvent interaction parameter and hydration of micelle. Partial specific volume and density of the micelle were obtained from the density measurements at various temperatures. The effect of modifying the end group of the hydrophilic block was investigated by comparing the behavior of trimethylammonium‐ and dimethylamino‐tipped copolymers, designated TE40B18, and DE40B18, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

6.
The structure and optical properties of the complex formed in the crystal phase of PVA that is caused by soaking at very high iodine concentration are investigated. In the resonance Raman spectra of lightly and heavily iodinated specimens, two Raman shifts appeared at 109 and 161 cm?1. The 109 cm?1 peak due to the I mode was much stronger than the 161 cm?1 peak in a heavily iodinated specimen, whereas the peak was comparable with the 161 cm?1 peak in a lightly iodinated specimen. The complex formed in the crystal phase is identified as the I mode complex. It has an averaged iodine–iodine distance of 3.2 Å, which is different from the 3.08 Å of the I mode complex formed in the amorphous phase. The effect of KI concentration in the soaking solution on the formation of the complex is also examined. The increased KI concentration in the soaking solutions at a fixed iodine concentration increases the amount of the complex formed in the crystal phase. The change in the hydrogen-bonding state in the crystal phase with the complex formation can be evidenced by IR and NMR. © 1994 John Wiley & Sons, Inc.  相似文献   

7.
Systems that are capable of removing highly toxic anions from wastewater effluents, even at extremely low concentrations, are a major need in the defense industry. This study reports on the features of two new batch and continuous‐flow sorption processes with regard to ultimate removal and recovery of the perchlorate (ClO) anion from ammonium perchlorate (NH4ClO4) wastewater. The sorbent developed is a crosslinked poly(allylamine hydrochloride) (PAA·HCl) polymeric hydrogel. The pH‐sensitive PAA·HCl hydrogels were synthesized by chemically crosslinking a solution of linear PAA·HCl chains with epichlorohydrin (EPI). The perchlorate‐binding capacity of the polymer gels was measured in standard solutions and studied as a function of gel synthesis parameters. Equilibrium perchlorate loadings of 5770 ± 870 mg ClO/g gel were calculated from measurement of the decrease in perchlorate concentration in aqueous standard solutions using UV‐Vis spectrophotometry. Batch experiments in wastewater originating from the Naval Surface Warfare Center (NSWC) Indian Head Division showed that perchlorate concentrations decreased by 85%. Preliminary lab‐scale packed‐column experiments in wastewater achieved up to 40% reduction in total perchlorate content. The regeneration ability of the gels was demonstrated by release of the bound perchlorate anions, upon washing with a 1N NaOH solution, providing opportunities to recover and reuse the hydrogel over multiple regeneration cycles. The PAA·HCl hydrogels are demonstrated to be appropriate materials for treating wastewaters that contain ammonium perchlorate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2073–2083, 2001  相似文献   

8.
The composites of the polypyrrole (PPy) and polyelectrolyte copolymers (PE) were prepared by electrochemical polymerization. The various compositions of the polyelectrolyte copolymers were used as a dopant, and were composed of copolymers of water‐soluble polymers and 2‐Acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS). Thermally sensitive (N‐isopropyl acrylamide, NiPAAm) and insensitive (acrylamide, AAm) polymers were used as the water‐soluble polymer. The electrochemical activity and mass change during the redox process of the PPy composites were investigated by potentiodynamic voltametry and electrochemical quartz crystal microbalance (EQCM). The mass change during the redox process was mainly concerned with the cation in the electrolyte solution. When the electrochemical activity of the PPy was larger than the amount of the polyelectrolyte anion (AMPS), the insertion/expulsion of the monoanion (ClO) into/from the PPy composite also occurred to ionically bond with the PPy in the redox process. The PPy/P(NiPAAm/AMPS) shows a significant mass decrease with increasing the temperature compared with the PPy/P(AAm/AMPS). The transition temperature of the PPy/P(NiPAAm/AMPS) is higher in the oxidized state than in the reduced state. The transition temperature of PPy composite increases with the composition of the hydrophilic electrolyte (AMPS). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 311–321, 1999  相似文献   

9.
Investigations on the Counter Ion Structure of the Cationics Polymerization of Isobutylvinylether with Iodine Based Systems The structure of counter ions of iodine based initiators for the cationic polymerization of isobutylvinylether is elucidated by means of u.v.-spectroscopy using as model system: Increasing electrophilicity of the cation causes a decrease of the counter ion stability. High concentrations of iodine lead to the formation of polyiodides, as I and I, respectively. The influence on chain propagation by iodine and monomer concentration as well have been followed by GPC and u.v.-spectroscopy. Both influences, strongly affects the propagation reaction. Triphenylmethylbromide in conjunction with iodine is a convenient initiating system, realizing a long living and transfer suppressed propagation, when solvents of higher polarity are used. An activated carbon-halide bond is concluded to be the active species.  相似文献   

10.
The elastic constants of closed mesh braided/woven fabrics are generally obtained from finite element analysis, fabric geometry model, and modified classical laminate plate theory. These models are complex and often impractical for industrial design purposes and do not address the cases of open mesh braided/woven fabrics. This paper proposes an alternative to existing models and software packages. Simple regression‐based empirical equations were developed to obtain Ex, Ey, Gxy, and νxy of braided/woven fabrics at any angle‐ply angle using the braid/weave unit cell volume fraction (Vf0), the fiber volume fraction (Vf), and the elastic constants of an equivalent angle‐ply laminate (E, E, G, ν). Design equation predictions were verified by comparing them to a previously validated modified classical laminate plate theory (CLPT) model using various fiber/resin combinations. Excellent agreement was found for each set of results. POLYM. COMPOS., 26:152–164, 2005. © 2005 Society of Plastics Engineers  相似文献   

11.
The atom‐transfer radical polymerization (ATRP) of methyl methacrylate (MMA), using α,α′‐dichloroxylene as initiator and CuCl/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst was successfully carried out under microwave irradiation (MI). The polymerization of MMA under MI showed linear first‐order rate plots, a linear increase of the number‐average molecular weight with conversion, and low polydispersities, which indicated that the ATRP of MMA was controlled. Using the same experimental conditions, the apparent rate constant (k) under MI (k = 7.6 × 10?4 s?1) was higher than that under conventional heating (k = 5.3 × 10?5 s?1). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2189–2195, 2004  相似文献   

12.
The existence of structural order is found in the polyacrylonitrile (PAN)-iodine complex obtained by immersing PAN film in an aqueous solution of I2/KI. We provide an interpretation for the key features of this structural order and for the structural change of PAN by iodine sorbing. The observed diffractions suggest that iodine penetrates into the crystalline phase of PAN at relatively low iodine concentrations and are intercalated between PAN molecular cylinders in the form of polyiodine columns that are composed mainly of I (most likely the I2/I complex). Pseudohexagonal crystals of PAN are expanded uniaxially by replacement of PAN molecular cylinders by the polyiodine columns. The intercalated polyiodine column layers are arrayed parallel with PAN chain layers in the crystalline phase. The results led to a proposal of an intercalation model for the crystalline structure of the PAN–iodine complex. The crystalline structures are expected to exist with two different types of the polyiodine layers. The crystalline transition between these structures occurs by thermal mobility of PAN chains. © 1994 John Wiley & Sons, Inc.  相似文献   

13.
Polyaniline (PANI) electrode was synthesized on a conducting indium tin oxide glass by in situ oxidative polymerization to construct a low production cost counter electrode of dye‐sensitized solar cell (DSSC). The scanning electron microscopy image showed that PANI electrode was a porous state with the particles diameter in 20–30 nm. The cyclic voltammogram measurement revealed that PANI electrode had smaller charge transfer resistance and higher electrocatalytic activity for I/I? redox reaction. The Brunauer–Emmett–Teller (BET) surface area of PANI was high to 53.114 m2/g, and the high surface area of PANI electrode benefited for the absorption of electrolyte. Finally, we compared the photoelectric properties of DSSC using the PANI counter electrode and platinized counter electrode. The results indicated the efficiency of DSSC with PANI electrode reached 2.64%, which was higher than that with platinized electrode (1.75%). Therefore, the PANI counter electrode with excellent catalytic performance is a potential substitute for platinized electrode to save cost of DSSC. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers  相似文献   

14.
To get more information on the structure of iodinated poly(vinyl alcohol) (PVA), thermal analyses of unoriented and oriented PVA films were conducted. Unoriented and oriented PVA films iodinated with aqueous solutions at selected concentrations were carried out by thermogravimetry (TG) and differential scanning calorimetry (DSC). The TG curves for the iodinated film shows four or five weight‐loss zones associated with degradation and evaporation of excess I2 molecules and I2 molecules from I, partial OH side groups on PVA, and I2 from I, the remaining OH groups and the partial main chains, the remaining main chains, and a very small amount of residue from PVA. The char of KI salts remained. By investigating the TG results, it was identified that the amount of I ions increased with increasing I2/KI up to 65%, but above that weight gain, the rate of increase diminished and the amount of I ions from the I ions increased. The TG curve for the oriented film was very similar to that for the unoriented film except for its greater weight loss at zone I due to narrow space in amorphous region. The DSC thermogram of iodinated films indicated two peaks at 145°C and 160–170°C, corresponding to the melting of crystals and the degradations of OH groups and main chains, respectively. The maximum temperatures of peaks were much lower than that of the untreated one. ©2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2407‐2415, 2004  相似文献   

15.
Poly(3‐mesityl‐2‐hydroxypropyl methacrylate) (PMHPMA) was synthesized in a 1,4‐dioxane solution with 2,2′‐azobisisobutyronitrile as the initiator at 60°C. The homopolymer and its monomer were characterized with 1H‐ and 13C‐NMR, Fourier transform infrared, differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and elemental analysis techniques. According to size exclusion chromatography analysis, the number‐average molecular weight, weight‐average molecular weight, and polydispersity index of PMHPMA were 65,864 g/mol, 215,375 g/mol, and 3.275, respectively. According to thermogravimetric analysis, the carbonaceous residue value of PMHPMA was 14% at 500°C. The values of the specific retention volume, adsorption enthalpy, sorption enthalpy, sorption free energy, sorption entropy, partial molar free energy, partial molar heat of mixing, weight fraction activity coefficient of solute probes at infinite dilution (Ω), and Flory–Huggins interaction parameter (χ) were calculated for the interactions of PMHPMA with selected alcohols and alkanes by the inverse gas chromatography method at various temperatures. According to Ω and χ, selected alcohols and alkanes were nonsolvents for PMHPMA at 423–453 K. Also, the solubility parameter of PMHPMA (δ2) was found to be 24.24 and 26.33 (J/cm3)0.5 from the slope and intercept of (δ/RT) ? χ/V1 = (2δ2/RT1 ? δ/RT at 443 K, respectively [where δ1 is the solubility parameter of the probe, V1 is the molar volume of the solute, T is the column temperature (K), and R is the universal gas constant]. The glass‐transition temperature of PMHPMA was found to be 386 and 385 K by inverse gas chromatography and differential scanning calorimetry techniques, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 101–109, 2006  相似文献   

16.
A novel ultraviolet (UV)‐curable monomer α,ω‐dichloropolysiloxane was synthesized by the telomerization of dichlorodimethylsilane and octamethylcyclotetrasiloxane (D4). The products with very low peel strength (<0.332 N/cm) could be used as release agents in pressure‐sensitive adhesives. Moreover, the values of the dispersion component of surface energy (γ) from the films of UV‐curable prepolymers (26.40–33.75 mJ/m2) were determined and the effects of γ on the reduction of adhesion were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2135–2139, 2002  相似文献   

17.
The polymerization kinetic of methacrylamide with the KMnO4/glycine redox system has been investigated volumetrically at 35±0.1°C under nitrogen atmosphere in aqueous sulfuric acid medium in a dimethylsulfoxide/H2O mixture (5% v/v). The rates of polymerization were found to obey the following equation: Rp ∝ [Methacrylamide]1.08[Glycine]0.44[KMnO]0.46. A glycine end group containing polymethacrylamide was prepared by the MnO/glycine redox system under mild conditions. The reaction proceeded with radical mechanism and the overall energy of activation (Ea) was calculated to be 29.87 kJ/mol from the Arrhenius plot in the temperature range 25–50°C. Molecular weight of the polymer was determined by viscometry. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3918–3924, 2003  相似文献   

18.
A range of fatty acid esters is now being produced commercially with immobilized microbial lipases (glycerol ester hydrolases; EC) in nonaqueous solvents. In this study, a synthetic hydrogel was prepared by the copolymerization of methacrylic acid and dodecyl methacrylate in the presence of a crosslinker, N,N‐methylene bisacrylamide. A purified alkaline thermotolerant bacterial lipase from Bacillus cereus MTCC 8372 was immobilized on a poly(methacrylic acid‐co‐dodecyl methacrylate‐clN,N‐methylene bisacrylamide) hydrogel by an adsorption method. The hydrogel showed a 95% binding efficiency for the lipase. The bound lipase was evaluated for its hydrolytic potential toward various p‐nitrophenyl acyl esters with various C chain lengths. The bound lipase showed optimal hydrolytic activity toward p‐nitrophenyl palmitate at a pH of 8.5 and a temperature of 55°C. The hydrolytic activity of the hydrogel‐bound lipase was enhanced by Hg2+, Fe3+, and NH ions at a concentration of 1 mM. The hydrogel‐bound lipase was used to synthesize geranyl acetate from geraniol and acetic acid in n‐heptane. The optimization of the reaction conditions, such as catalyst loading, effect of substrate concentration, solvent (n‐pentane, n‐hexane, n‐heptane, n‐octane, and n‐nonane), reaction time, temperature, molecular sieve (3 Å × 1.5 mm) and scale up (at 50‐mL level), was studied. The immobilized lipase (25 mg/mL) was used to perform an esterification in n‐alkane(s) that resulted in the synthesis of approximately 82.8 mM geranyl acetate at 55°C in n‐heptane under continuous shaking (160 rpm) after 15 h when geraniol and acetic acid were used in a ratio of 100 : 100 mM. The addition of a molecular sieve (3 Å × 1.5 mm) to the reaction system at a concentration of 40 mg/mL in reaction volume (2 mL) resulted in an increase in the conversion of reactants into geranyl acetate (90.0 mM). During the repetitive esterification under optimum conditions, the hydrogel‐bound lipase produced ester (37.0 mM) after the eighth cycle of reuse. When the reaction volume was scaled up to 50 mL, the ester synthesized was 58.7 mM under optimized conditions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

19.
The dispersion force component of surface free energy, γ, and the nondispersive interaction free energy between solid and water, I, were determined by the two-liquid contact-angle method, i.e., by the measurement of contact angles of water drops on plain solids in hydrocarbon, for commercialy available organic polymers such as nylons, halogenated vinyl polymers, polyesters, etc. A method to estimate the I values from the knowledge of the polymer composition is also proposed, on the basis of the assumption of the spherical monomer unit and the sum of interactions between functional groups and water molecules at the surface.  相似文献   

20.
Titanium dioxide (TiO2) nanoparticles were functionalized with toluene‐2,4‐diisocyanate and then polypropylene/polyamide 6/(PP/PA6) blends containing functionalized‐TiO2 were prepared using a twin screw extruder. Isothermal crystallization and melting behavior of the as‐prepared composites were investigated using differential scanning calorimetry and wide‐angle X‐ray diffraction. Isothermal crystallization analysis shows that the TiO2 nanoparticles have two effects on PP/PA6 blends, i.e., it can favor the improvement of crystallization ability and decrease the crystallization rate of PP/PA6 blends. The improvement of crystallization ability is superior over decreasement of crystallization rate of PA6 chains caused by TiO2, therefore PA6 in PP/PA6/TiO2 nanocomposites have higher crystallization rate than that of PA6 in pure PP/PA6 blends, which indicated TiO2 nanoparticles favored the crystallization of PA6. The TiO2 nanoparticles show no effects on the equilibrium melting temperature (T) values of PP phase but decreases the T values of PA6 phase. In addition, the TiO2 nanoparticles did not change the crystalline polymorph of PP/PA6 blends basically; however, favored the formation of β‐PP. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers  相似文献   

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