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     

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.     

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     

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.     

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.     

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     

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.     

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^*.     

Preparation and adsorption behavior for metal of chitosan crosslinked by dihydroxy azacrown ether

A new type of crosslinked chitosan was prepared using Dihydroxy azacrown ether as the crosslinking agent. Its structure was confirmed by elemental analysis, Fourier transform infrared (FTIR) spectra analysis, solid‐state ¹³C nuclear magnetic resonance (NMR) analysis, and X‐ray diffraction analysis. Its static adsorption properties for Ag⁺, Cd²⁺, Hg²⁺, and Co²⁺ were studied. The experimental results showed that the Dihydroxy azacrown ether crosslinked chitosan has good adsorption capacities and high selectivity for adsorption of Ag⁺ with the coexistence of Hg²⁺ and Co²⁺. The selectivity coefficients of crosslinked chitosan are k/ = 5.47, k/ = 4.64, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 530–535, 2002     

Variable‐energy positron lifetime study of silicon‐oxide films plasma deposited from hexamethyldisiloxane and oxygen mixtures

Mixtures of hexamethyldisiloxane [HMDSiO, (CH₃)₃SiOSi(CH₃)₃] and oxygen are plasma polymerized at different oxygen pressures (P = 1.3–11.4 Pa) and a fixed monomer pressure (P_m = 2.6 Pa). The discharge power is kept at 100 W throughout the work. Nanometer‐size holes in the deposited films are characterized by variable‐energy positron annihilation lifetime spectroscopy (PALS). Additional information on the film composition and structure is obtained by X‐ray photoelectron spectroscopy and IR absorption spectroscopy. The ortho‐positronium lifetime τ₃ and intensity I₃ increase with the P up to 6.2 Pa and then decrease with the P. PALS measurements after annealing at 400°C show that films prepared at high oxygen pressure have a less stable structure than a film deposited at a lower oxygen pressure. These results are discussed in comparison with plasma deposition of pure HMDSiO, as are the possible effects of oxygen radicals on the film structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 974–980, 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     

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     

Several features of vinyl chloride–diallyl phthalate suspension copolymerization

Vinyl chloride–diallyl phthalate (VC–DAP) suspension copolymerization was carried out in a 5‐L autoclave and 200‐mL stainless steel vessel at 45°C. The apparent reactivity ratios of VC–DAP suspension copolymerization system were calculated as r_VC = 0.77 and r_DAP = 0.37. It shows that VC–DAP copolymer contains no gel when the feed concentration of DAP (f) is lower than a critical concentration (f_cr, inside the range of 0.466–0.493 mmol/mol VC at 80–85% conversion), the polymerization degree (DP) of copolymer increases with the increase of f and conversion. VC–DAP copolymer is composed of gel and sol fractions when f is larger than f_cr. The DP of sol fraction decreases as f increases, but the gel content and the crosslinking density of gel increase. The gel content also increases as conversion increases. The results also show that the index of polydispersity of molecular weight of sol changes with f, a maximum value appears when f is close to f_cr. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 156–162, 2000     

Electrochemical synthesis and properties of poly(3‐methylthiophene): Novel synthesis of poly(3‐methylthiophene) with pentachlorostannate and hexachloroantimonate

Poly(3‐methylthiophene) (P3‐MeT) doped with different anions were prepared electrochemically in the presence of tetraalkylammonium salts. The new poly(3‐methylthiophene) SnCl and SbCl (P3‐MeT SnCl₅ and P3‐MeT SbCl₆) were prepared electrochemically using tetra‐n‐butylammonium pentachlorostannate and tetra‐n‐butylammonium hexachloroantimonate as the supporting electrolytes. The effect of current density, salt concentration, reaction temperature, and the nature of solvents on the polymer yield and polymer conductivities have been investigated. Cyclic voltammetry of poly(3‐methylthiophene) has been examined at platinum electrode in 1,2‐dichloroethane medium containing n‐Bu₄NSnCl₅, Bu₄NSbCl₆, and Bu₄NClO₄ as the supporting electrolytes in the range of −1.0 to 1.7 V versus SCE in the presence and absence of 3‐methylthiophene. Electrical conductivity, magnetic susceptibility measurements, and structural determination by elemental analysis and infrared studies were also made. Scanning electron microscopy revealed a globular, branched, fibrous and a spongy, fibrous morphology of poly(3‐methylthiophene) SnCl, ClO, and SbCl, respectively. The thermal analysis of the polymers was also investigated. Possible causes for the observed lower conductivity of these polymers have also been discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 91–102, 1999     

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     

Relationship in polypropylene melt between its linear viscoelasticity and its steady capillary flow properties

It is the object of the present study to obtain clear knowledge of the relations in the polypropylene melt between its linear viscoelasticity and its nonlinear steady capillary flow, paying particular attention to the elastic properties in its capillary flow. By representing the linear viscoelasticity numerically with zero-shear viscosity, η₀, and steady-state compliance, J, evaluation has been made of the properties concerning the elasticity of polymer melt in the capillary flow, such as non-Newtonianity, the entrance pressure loss, the end correction, the Barus effect, and the melt fracture. The steady flow viscosity η, the entrance pressure loss P₀, the critical shear stress, τ_c, and the critical shear rate $\dot \gamma _c$ at which melt fracture begins to occur are subject to η₀ as follows: From the well-known relationship between η and the weight-average molecular weight M?_w, these quantities are governed by M?_w. Meanwhile, for such quantities as structural viscosity index N, end correction coefficient ν, and elastic pressure loss ratio P₀/P, following correlations hold: As η₀ and J are respectively determined mainly by M?_w and the molecular weight distribution MWD, these quantities are governed by both M?_w and MWD. Physical meanings of η₀·J and η₀² · J are, respectively, mean relaxation time and a measure of stored energy in steady flow. The Barus effect has a positive correlation to J, ν, and P₀/P. (The symbol ∝ employed here means positive correlation.)     

Morphological studies of the modified materials: Low-density polyethylene/poly(acrylic acid)/europium(III) and low-density polyethylene/poly(acrylic acid)/uranyl ion

The morphology of low-density polyethylene (LDPE) modified by in situ sorption and thermal polymerization of acrylic acid (AA) in the matrix was examined. The microstructure of the LDPE/poly(acrylic acid) (PAA) materials after Eu³⁺ and UO ion exchange was investigated. The phase behavior of these materials was analyzed using X-ray diffraction, scanning electron microscopy (SEM), and thermal measurements (DSC). The X-ray dif-fraction studies showed that PAA is located at amorphous region of the matrix. The LDPE/PAA surface, as investigate by SEM, was apparently homogeneous before and after Eu³⁺ and UO ion exchange, respectively. Two T_g values were found for the LDPE/PAA material before and after Eu³⁺ ion exchange. Also, three and four T_g values were found for LDPE/PAA after UO ion exchange depending on the amount of UO in the modified matrix. This indicates microphase domains in the LPDE/PAA-, LPDE/PAA/Eu³⁺-, and LPDE/PAA/UO -modified materials, although a lack of visible phase separation in the micrographs was observed. © 1996 John Wiley & Sons, Inc.     

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.     

The effect of side chains on the partial specific volumes of poly(o-alkylphenyl methacrylate)s and polydiitaconates

Partial specific volumes ν of a series of poly(o-alkyl phenyl methacrylate)s and polydiitaconates were determined by density measurements, in toluene and tetrahydrofuran solutions, respectively. The effect of the size and nature of the side groups on partial specific volume is analyzed. Good agreement is found between the experimental ν values and those obtained theoretically from the group contribution method.     

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.