Synthesis,characterization, and adsorption properties of chitosan azacrown ethers bearing hydroxyl group

Two new chitosan azacrown ethers bearing hydroxyl groups (CTS‐DH and CTS‐DO) were synthesized by the reaction of 3‐hydroxyl‐1,5‐diaza‐cycloheptane and 3‐hydroxyl‐1,5‐diaza‐cyclooctane with epoxy‐activated chitosan. Their structures were characterized by elemental analysis, infrared spectra analysis, and X‐ray diffraction analysis. The adsorption and selectivity properties of the hydroxyl azacrown ethers chitosan derivatives for Ag⁺, Cr³⁺, Cd²⁺, and Pb²⁺ were also investigated. The experimental results showed that the two novel chitosan azacrown ethers have good adsorption capacity for Ag⁺, and also showed that the grafted chitosan azacrown ethers have high selectivity for the adsorption of Ag⁺ in the presence of Pb²⁺ and Cd²⁺. The selectivity coefficients of CTS‐DH and CTS‐DO were K = 21, K = 42, K = 20.5, K = 41, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1793–1798, 2001     

Synthesis and adsorption properties of metal ions of novel azacrown ether crosslinked chitosan

Azacrown ether chitosan (CTSC) was synthesized by the reaction of chitosan with N‐allyl benzo 15‐crown‐5 crown ether. Azacrown ether crosslinked chitosan (CCTSC) was prepared by the crosslinked reaction of CTSC and epichlorodydrin. Their structures were confirmed by infrared spectral analysis and X‐ray diffraction analysis. The adsorption properties of CTSC and CCTSC for metal ions were also investigated. The experimental results showed that the two chitosan derivatives not only had a good capacity to adsorb Pd²⁺ and Ag⁺ but also was highly selective for Pd²⁺ and Ag⁺ in the coexistence system containing other metal ions. At 20°C ± 1°C and pH = 4, the adsorption capacity of CTSC and CCTSC for Pd²⁺ was 186.1 and 173.1 mg/g, respectively; and for Ag⁺ was 90.2 and 56.5 mg/g, respectively. The selectivity coefficients were K = 6.99, K = ∞, K = 35.38, K = ∞ for CTSC and K = 10.66, K = ∞, K = 85.45, K = ∞ for CCTSC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2705–2709, 2006     

Preparation and characterization of dihydroxyl mesocyclic diamine derivative of chitosan

The synthesis of a new dihydroxyl mesocyclic diamine grafting chitosan is presented. This derivative is formed by reaction of dihydroxyl azacrown ether with expoxy‐activated chitosan. The obtained copolymer contains amino functional groups in its skeleton and the secondary amine, and more polar hydroxyl groups. Elemental analysis, fourier transform infrared analysis, as well as solid‐state carbon‐13 nuclear magnetic resonance analysis were used to characterize chemical modifications of the chitosan. The adsorption properties of the dihydroxyl mesocyclic diamine grafted chitosan for Ag⁺, Pb²⁺, Cd²⁺, and Cr³⁺ were studied. The experimented results showed that the novel chitosan derivative has good adsorption capacity and high selectivity for Ag⁺ in the presence of Pb²⁺, Cd²⁺, and Cr³⁺, and its adsorption selectivity is better than that of chitosan. The selectivity coefficients were K = 12.25, K = 6.12, and K = 0.52, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2677–2681, 2002     

Study on the adsorption properties of novel crown ether crosslinked chitosan for metal ions

We first synthesized N‐benzylidene chitosan (CTB) by the reaction of benzaldehyde with chitosan (CTS). Chitosan‐dibenzo‐18‐crown‐6 crown ether bearing Schiff‐base group (CTBD) and chitosan‐dibenzo‐18‐crown‐6 crown ether (CTSD) were prepared by the reaction of 4,4′‐dibromodibenzo‐18‐crown‐6 crown ether with CTB and CTS, respectively. Their structures were confirmed by Fourier transform infrared spectral analysis and X‐ray powder diffraction analysis. These novel crown ether crosslinked CTSs have space net structures with embedded crown ethers and contain the double structures and properties of CTS and crown ethers. They have stronger complexation with and better selectivity for metal ions than corresponding crown ethers and CTS. Moreover, these novel CTS derivatives can be used to separate and preconcentrate heavy or precious metal ions in aqueous environments. From this practical viewpoint, we studied the adsorption and selectivity properties of CTB, CTBD, and CTSD for Ag⁺, Cu²⁺, Pb²⁺, and Ni²⁺. The experimental results showed that CTBD had better adsorption properties and higher selectivity for metal ions than CTSD. For aqueous systems containing Pb²⁺–Ni²⁺ and Pb²⁺–Cu²⁺, the selectivity coefficients of CTSD and CTBD were K/Ni²⁺ = 24.4 and K/Cu²⁺ = 41.4 and K/Ni²⁺ = 35.5 and K/Cu²⁺ = 55.3, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 29–34, 2002; DOI 10.1002/app.10180     

Synthesis and characterization of macrocyclic polyamine derivative of chitosan

A novel macrocyclic polyamine derivative of chitosan was synthesized by a reaction between chitosan and epoxy‐activated macrocyclic polyamine. The copolymer that is obtained contains amino functional groups in its skeleton and secondary amine and more polar hydroxyl groups. Four types of analyses were used to characterize the chemical modifications of the chitosan: elemental, FTIR spectra, solid‐state ¹³C‐NMR, and X‐ray diffraction. The adsorption properties of the macrocyclic polyamine grafted chitosan for Ag⁺, Cu²⁺, Co²⁺, and Cr³⁺ were also investigated. The experimental results showed that the new macrocyclic polyamine derivative of chitosan has high adsorption capacity and good selectivity for Ag⁺ in the presence of Ag⁺, Co²⁺, and Cr³⁺. The selectivity coefficients were K = 6.16, K = 14.81, and K = 2.42, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 924–929, 2003     

Composition and temperature effects on air separation through liquid crystalline alkyl cellulose membranes

The air separation through triheptyl cellulose (THC)/ethyl cellulose (EC) blend membranes containing no more than 20 wt % THC at the temperature range from 298 to 358 K was investigated using a variable volume method. The air-separation ability for the THC/EC membranes were greater than that for the THC-free pure EC membrane. P for the THC/EC membranes was between 1.06–8.89 × 10^?9 cm³ (STP) cm/cm² s cmHg and P/P 3.04–3.66. The THC/EC membrane showed a unique trend in its P/P ? P relationship, i.e., the magnitude of P/P increased simultaneously with that of P. The THC/EC membrane yielded a maximum oxygen concentration in the oxygen-enriched air (OEA) of 39.5% at an OEA flux of 6.99 × 10^?4 cm³ (STP)/s cm² for a pressure difference of 0.43 MPa at 358 K. After 300 h of measurement at 0.40 MPa and 313 K, the efficiency of the concentrating oxygen was almost constant. © 1994 John Wiley & Sons, Inc.     

Permeability of dense (homogeneous) cellulose acetate membranes to methane,carbon dioxide,and their mixtures at elevated pressures

Mean permeability coefficients for CH₄ and CO₂ (P̄ and P̄) in cellulose acetate (CA, DS = 2.45) were determined at 35°C (95°F) and at pressures up to about 54 atm (800 psia). The measurements were made with pure CH₄ and CO₂ as well as with CH₄/CO₂ mixtures containing 9.7, 24.0, and 46.1 mol % CO₂. In the measurements with the pure gases, P̄ was found to decrease with increasing pressure, as expected from the “dual-mode” sorption model. By contrast, P̄ passes through a minimum and then increases with increasing pressure, probably due to the plasticization (swelling) of CA by CO₂. The values of P̄ and P̄ determined with the mixtures containing 9.7 and 24.0 mol % CO₂ decrease with increasing total pressure; this behavior is adequately described by the extended “dual-mode” sorption model for mixtures. By contrast, the values of P̄ and P̄ obtained with the mixture containing 46.1 mol % CO₂ pass through a minimum and then increase as the total pressure is raised, probably also due to the plasticization of CA by CO₂. The CO₂/CH₄ selectivity (≡P̄/P̄) of the CA membrances decreases with increasing total pressure and, at constant pressure, decreases with increasing CO₂ concentration in the feed mixture. The effects of exposing the CA membranes to high-pressure CO₂ prior to the permeability measurements (“conditioning” effects) on P̄ and P̄ have also been studied. © 1996 John Wiley & Sons, Inc.     

Application of poly(phthalazinone ether sulfone ketone)s to gas membrane separation

A series of poly(phthalazinone ether sulfone ketone) (PPESK) copolymers containing different component ratios of bis(4‐fluorodiphenyl) ketone and bis(4‐chlorodiphenyl)sulfone with respect to a certain amount of 4‐(4‐hydroxyphenyl)‐2,3‐phthalazin‐1‐one were synthesized by polycondensation. Glass transition temperatures of these polymers were adjusted from 263°C to 305°C by changing the ratios of reactants. Gas permeability and selectivity of the dense membranes of the polymers for three kinds of gases (CO₂, O₂, and N₂) were determined at different temperatures. The result indicated that the membrane of PPESK (S/K = 1/1, mol ratio) had an excellent gas separation property. Permeability of the polymer membranes for CO₂, O₂, and N₂ was P = 4.121 barrier, P = 0.674 barrier, and P = 0.0891 barrier, respectively. Separation factors of α and α were 7.6 and 46, respectively. New material was made into a composite membrane with silicone rubber for blocking up leaks and defects on the surface of its nonsymmetrical membrane. As a result of the test, permeability of the composite membrane was J = 7.2 × 10⁻⁶ cm³ (STP) cm⁻² S⁻¹ cm⁻¹ Hg and J = 0.99 × 10⁻⁶ cm³ (STP) cm⁻² S⁻¹ cm⁻¹ Hg, whereas the α was still higher than 7. These showed that PPESKs had a bright prospect as the potential membrane material for high‐temperature gas separation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2385–2390, 1999     

Gas permeabilities of poly(trimethylsilylpropyne) membranes surface modified with CF4 plasma

Surface fluorination of poly(trimethylsilylpropyne) (PTMSP) membranes by CF₄ plasma was studied. The surface fluorination of the membranes was carried out in an atmosphere of CF₄ in a capacitively coupled discharge apparatus with external electrodes. Dramatic increase in selectivity (P/P) was observed. The effect of fluorination conditions such as duration of treatment and discharge power on the permeabilities of the membranes was studied. X-ray photoelectron spectrometric data of modified PTMSP membranes showed a drastic alternation in the surface layer. The P and P/P of the membranes were observed to be dependent on the F/C atomic ratio. At F/C > 1, the P/P value of the membranes could be more than four. © 1993 John Wiley & Sons, Inc.     

Oxygen/nitrogen transport in ionomer composite membranes containing a cobalt Schiff base complex

Different amounts of (N,N′‐disalicylideneethylenediamin)cobalt (CoS) were blended to a cobalt (II)‐neutralized sulfonated EPDM (Co^(II)‐S‐EPDM) ionomer membrane to enhance its oxygen‐enriching ability. Various influence factors on permeabilities and selectivities of the composite membranes, such as the gas pressure difference, the CoS content, and the testing temperature have been investigated. Oxygen permeability coefficients (P) and oxygen/nitrogen separation factors (α) increased simultaneously by decreasing the gas pressure difference or by increasing the CoS content. In comparison with the EPDM matrix, P and α of Co^(II)‐S‐EPDM–CoS (85/15) composite membrane increased from 11.0 Barrer and 4.38 to 37.0 Barrer and 9.60. Obvious enhancement in the oxygen‐enriching property shows that the dual actions of cobaltous ion crosslinking and addition of an abundant cobalt complex may be an effective way to improve a rubbery polymer membrane. As high as 15 wt % of the CoS could be blended. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1071–1077, 1999     

Intrinsic birefringence of nylon 6

Different values are reported in the literature for the intrinsic birefringence of the crystalline (Δn) and the amorphous (Δn) phases in nylon 6. Mostly, these values have either been determined by extrapolation (and then it is assumed that Δn = Δn) or calculated theoretically. In this study, intrinsic birefringence values Δn and Δn for nylon 6 were determined using the Samuels two-phase model which correlates sonic modulus with structural parameters. Three series of fiber samples were used: (1) isotropic samples of different degrees of crystallinity for estimation of E and E moduli at two temperatures. The following modulus values were obtained: 1.62 × 10⁹ and 6.66 × 10⁹ N/m² for 28.5°C, and 1.81 × 10⁹ and 6.71 × 10⁹ N/m² for ?20°C; (2) anisotropic, amorphous fiber samples for estimation of Δn = 0.076 and E = 1.63 × 10⁹ N/m² at 28.5°C; (3) semicrystalline samples of various draw ratios for estimations of Δn = 0.089 and Δn = 0.078. All measurements were carried out with carefully dried samples to avoid erroneous results caused by moisture.     

Sorption and transport properties of the semi‐interpenetrating network based on crosslinked poly(vinyl alcohol) and poly(styrene sulfonic acid‐co‐maleic anhydride) as proton‐conducting membranes

This study investigates the sorption and transport properties of hydrocarbon membranes based on poly(vinyl alcohol) network and poly(styrene sulfonic acid‐co‐maleic acid) (PSSA‐MA). The water and methanol self‐diffusion coefficients through an 80 wt % PSSA‐MA interpenetrating SIPN‐80 membrane measured 3.75 × 10^?6 and 5.47 × 10^?7 cm²/s, respectively. These results are lower than the corresponding values of Nafion® 115 (8.89 × 10^?6 cm²/s for water and 8.63 × 10^?6 cm²/s for methanol). The methanol permeability of SIPN‐80 membrane is 4.1 × 10^?7 cm²/s, or about one‐fourth that of Nafion® 115. The difference in self‐diffusion behaviors of Nafion® 115 and SIPN‐80 membranes is well correlated with their sorption characteristics. The solvent uptake of Nafion® 115 increased as the methanol concentration increased up to a methanol mole fraction of 0.63, and then decreased. However, the solvent uptake of the SIPN‐80 membranes decreased sluggishly as the methanol concentration increased. The λ values of water and methanol (i.e., λ and λ) in Nafion® 115 are quite close, indicating no sorption preference between water and methanol. In contrast, the λ value is only one‐third λ for a SIPN‐80 membrane. Accordingly, the SIPN membranes are regarded as candidates for direct methanol fuel cell applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Hybrid organic/inorganic dendritic triblock copolymers: Synthesis,nanostructure characterization,and micellar behavior

A new class of amphiphilic dendritic ABA triblock copolymers, which is based on organic linear polyethylene oxide (PEO) and inorganic dendritic carbosiloxane (CSO) was synthesized. The strategy used in synthesizing these materials is based on divergent method using hydrosilylation‐alcoholysis cycles. The reaction conditions and structural features of dendrimers were analyzed by different physicochemical techniques such as: GPC, NMR, UV spectroscopy, DSC, and viscometry. The generational limit of dendrimer after the first generation, OSC‐D‐PEO‐D‐CSO, forced us to employ HSiCl₂CH₃ as branching reagent. Also further hydrosilylation of the third generation yielded an irregular structure species. Self‐assembling and morphological studies of first, OSC‐D‐PEO‐D‐CSO, and second, OSC‐D‐PEO‐D‐CSO, generations in aqueous medium were monitored by using fluorescence, TEM and DLS techniques. However, the dendritic block copolymer with third generation, OSC‐D‐PEO‐D‐CSO, could not be dispersed in aqueous phase. The diameters of denderitic micelles had a narrow distribution in the ranges of 69 and 88 nm, respectively. Although the micelles were stable even in first generation, partition equilibrium constants of pyrene and critical micelle concentration in both of dendritic micelles imply that the micellar behaviors of the supramolecules strongly depend on the hydrophobic block's size in which increasing generation effectively promoted the micelle formation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Facilitated transport of oxygen in ethyl cellulose membranes containing cobalt porphyrins as oxygen carriers

Facilitated transport of oxygen was investigated in ethyl cellulose membranes containing cobalt(II) meso‐tetrakis (substituted phenyl) porphyrins [CoTPP, CoT(2‐Cl)PP, CoT(4‐Cl)PP, CoT(4‐MeO)PP, and CoT(2,4‐2MeO)PP] as fixed oxygen carriers. The oxygen permeability (P) and oxygen/nitrogen selectivity (P/P) of the membranes containing oxygen carriers increase with a decrease in the upstream gas pressure, but the nitrogen permeability (P) is almost independent of the upstream nitrogen pressure. This indicates that the fixed oxygen carriers in the polymer membranes can reversibly interact with oxygen and facilitate oxygen transport in the membranes. The study on the influences of the substituents in the cobalt(II) porphyrins and the fifth ligand (imidazole or pyridine) on the membrane permeation behaviors shows that the porphyrin complex with an electron‐accepting substituent in the meso‐phenyl ring or with imidazole as the fifth ligand could increase the permeability and oxygen/nitrogen selectivity of the membranes much more than that with an electron‐donating substituent or with pyridine as the fifth ligand. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 484–488, 2000     

Elastic characteristics of branched-network polymers

The computed dependencies of elastic characteristics of branched-network polymers were obtained on the basis of the Takayanagi series model. The moduli ratio (λ) for branched-network and branched polymers increases as a result of an increase of the moduli ratio of network and branched phases (E/E) and the network phase fraction (V_net). The λ-increase as a function of V_net is larger than in the case of the E/E dependence. On the basis of computed dependencies, the experimental results for the radiation crosslinked SBS block copolymer were considered. The experimental results agree with the computed de-pendencies for the hetergeneous branched-network polymers with E/E ≈︁ 20. The influence of entanglements on the elastic characteristics of branched-network polymers is discussed. © 1996 John Wiley & Sons, Inc.     

A zeolite/polymer membrane for separation of ethanol-water azeotrope

A novel membrane effective in the separation of ethanol-water mixtures by pervaporation was made by combining zeolite NaA and poly(vinyl chloride) modified by 2-(2′-butoxyethoxy)ethyl thiolate. Under ambient conditions, a separation factor (α) of 29 and pervaporability (P) of 4 × 10^?4 g m^?1 h^?1 were obtained for the azeotropic mixture whereas, in the absence of zeolite, the respective values were 7 and 7 × 10^?5. A mechanism was proposed relating the preferential water transport at ≈? 50% zeolite content to an interfacial “phase” between the zeolite and the modified polymer.     

Forced oscillations in continuous flow stirred tank reactors with nonlinear step growth polymerization

The self-step growth polymerization of RA_f monomers in homogeneous, continuous flow stirred tank reactors (HCSTRs) is simulated under conditions of periodic feed concentration (with frequency ω and amplitude α). By having periodic operation, the polydispersity index of the polymer is found to increase by about 35% over the values at steady state. Periodic operation of HCSTRs is found to lead to gelation only for certain values of the frequency and the dimensionless residence time τ^*. Gelling envelopes have been obtained to give conditions under which HCSTRs should be operated. These envelopes can be described in terms of two critical dimensionless residence times, τ and τ such that nongelling operation is always ensured when τ^* < τ. For τ^* > τ, periodic operation always leads to gelation, and HCSTRs cannot be used. For τ < τ^* < τ, the gelling behavior is found to depend on the functionality f, amplitude α, and the dimensionless residence time τ^*.     

Influence of anionic form on thermal degradation of TMAHP–cellulose

Trimethylammoniumhydroxypropyl (TMAHP)–cellulose in 10 anionic forms (F^?, Cl^?, Br^?, I^?, HSO, NO, OH^?, HCO, H₂PO, CH₃COO^?) was prepared, and the influence of each anion on thermal degradation in inert atmosphere was studied. With the help of dynamic and isothermal thermogravimetry (TG) it was found that H₂PO ions had the greatest retarding effect on TMAHP–cellulose degradation. From the values of rate constants it can be seen that all ionic forms of TMAHP–cellulose have the starting rate of thermal degradation greater than unmodified cellulose. The calculated values of activation energy of thermal degradation for different ionic forms are decreasing in following sequence: H₂PO > F^? > NO > I^? > Br^? > HCO > Cl^? > HSO > OH^? > unmodified cellulose > CH₃COO^?. From the results of pyrolyse measurements in combination with gas chromatography and mass spectrometry (Py–GC–MS) it follows that the products of the elimination of quarternary ammonium salts are trimethylamine, 3-hydroxy-2-propanone, and, in the case of OH^? form, water. In all other ionic forms the third product is the corresponding acid.     

Study on the thermal stability of heterogeneous nucleation effect of polypropylene nucleated by different nucleating agents

The thermal stability of the heterogeneous nucleation effect of polypropylene (PP) nucleated with an organic phosphate (A) and two kinds of sorbitol derivatives (B and D) was investigated by DSC multiscanning. For pure PP, the peak temperature of crystallization (T) was little changed with an increasing number of DSC scans, indicating that nucleation of PP is thermally stable. For the PP nucleated with an organic phosphate (PPA), the temperatures at the onset of crystallization (T) and at the completion of crystallization (T); the peak temperature of crystallization (T) and melting (T); and the heat of crystallization (ΔH_c) and fusion (ΔH_m) of PP are higher than those of pure PP and were little influenced with an increasing number of DSC scans. For PP nucleated with the sorbitol derivatives (PPB and PPD), the T, T, T, and T decreased with an increasing the number of scans. These results indicated that the thermal stability of heterogeneous nucleation effect of the nucleating agent A is higher than that of nucleating agents B and D. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1643–1650, 2002     

Mass transport process for the adsorption of Cr(VI) onto water‐insoluble cationic starch synthetic polymers in aqueous systems

Dynamic adsorption behaviors between Cr(VI) ion and water‐insoluble amphoteric starches was investigated. It was found that the HCrO ion predominates over the initial pH ∼ 2–4, the CrO ion predominates over the initial pH ∼ 10–12, and both ions coexist over the initial pH ∼ 6–8. The sorption process occurs in two stages: the external mass transport process occurs in the early stage and the intraparticle diffusion process occurs in the long‐term stage. The diffusion coefficient of the early stage (D₁) is larger than that of the long‐term stage (D₂) for the initial pH 4 and pH 10. The diffusion rate of HCrO ion is faster than that of CrO ion for both processes. The D₁ and D₂ values are ∼ 1.38 × 10⁻⁷–10.1 × 10⁻⁷ and ∼ 0.41 × 10⁻⁷–1.60 × 10⁻⁷ cm² s⁻¹, respectively. The ion diffusion rate in both processes is concentration dependent and decreases with increasing initial concentration. The diffusion rate of HCrO ion is more concentration dependent than that of CrO ion for the external mass transport process. In the intraparticle diffusion process, the concentration dependence of the diffusion rate of HCrO and CrO ions is about the same. The external mass transport and intraparticle diffusion processes are endothermic and exothermic, respectively, for the initial pH 4 and pH 10. The k_d values of the external mass transport and intraparticle diffusion processes are ∼ 15.20–30.45 and ∼ −3.53 to −12.67 kJ mol⁻¹, respectively. The diffusion rate of HCrO ion is more temperature dependent than that of CrO ion for both processes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2409–2418, 1999