Gas transport in poly(alkoxyphosphazenes)

The permeability of four structurally related poly(alkoxyphosphazenes), three isomers of poly(dibutoxyphosphazenes) (PBuP), and poly(di-neopentyloxyphosphazene) (Pneo-PeP), to 13 gases has been determined by the time-lag method. Systematic variations in chemical structure have shown a large effect of side chains on permeabilities and permselectivities. The permeability of poly(di-n-butoxyphosphazene) (Pn-BuP) is of the order of 10^?8 cm³ (STP) cm/(cm² s cmHg) for many gases, and the value for a large gas is higher than that for a smaller one. For small gases such as He and H₂, poly(di-sec-butoxyphosphazene) (Ps-BuP) is as permeable as Pn-BuP, but its diffusivities for larger gases such as Xe and C₃H₈ are about one order lower than those of Pn-BuP. While the permselectivity of Pn-BuP is determined by the solubility, that of Ps-BuP depends on both the diffusivity and solubility factors. The property of poly(diisobutoxyphosphazene) (Pi-BuP) is intermediate between them. These polymers are constitutionally identical, and the only difference is the arrangements of carbons in the side groups. As the side chains become bulky, the permeability decreases, whereas the permselectivity increases. Further decreases of diffusivity and then permeability are observed for Pneo-PeP, whose side groups have one more methyl group than does Pi-BuP. But the solubility data are not much different from other three polymers and the diffusivity factor becomes more significant in permselectivity. The diffusivity depends on the polymer structure much more than does the solubility. The relationships between chemical structure and gas diffusivity and solubility are discussed.     

Synthesis and gas permeability of ester substituted poly(p-phenylene)s

Polymerizations of various ester substituted 2,5-dichlorobenzoates [substituent: linear alkyl groups (1a-f), branched alkyl groups (1g-l), cyclohexyl groups (1m-o), phenyl groups (1p-r), and oxyethylene units (1s-v)] were investigated with Ni-catalyzed/Zn-mediated system in 1-methyl-2-pyrrolidone (NMP) at 80 °C. Most of monomers bearing linear and branched alkyl groups successfully polymerized to give relatively high-molecular-weight polymers (M_n = 10,000-20,800). However, the molecular weight of the polymer having eicocyl groups was low because of steric hindrance of long alkyl chain. The polymerizations of cyclohexyl 2,5-dichlorobenzoate and phenyl 2,5-dichlorobenzoate produced low-molecular-weight polymers, while the polymerizations of monomers with alkyl cyclohexyl and alkyl phenyl groups proceeded to afford polymers with relatively high-molecular-weights. The polymers possessing oxyethylene units were obtained, but the molecular weights were low when the oxyethylene chains were long. The gas permeability of membranes of poly(p-phenylene)s with alkyl chains increased as increasing the length of alkyl chain. The membranes of poly(p-phenylene)s with phenyl groups and oxyethylene units exhibited high densities and relatively low gas permeability. However, the CO₂/N₂ separation factor of membrane of poly(p-phenylene) having oxyethylene units was as large as 73.6.     

Chelate membrane from poly(vinyl alcohol)/poly(N-salicylidene allyl amine) blend. III. Effect of Mn(II) and Co(II) on oxygen/nitrogen separation

Facilitated transport of oxygen through Co(II) and Mn(II) chelate membranes from poly(vinyl alcohol)/poly(N-salicylidene allyl amine) was investigated. As the membranes became chelated, oxygen diffusivity decreased and the solubility toward oxygen was enhanced. The oxygen permeability of the base poly(vinyl alcohol)/poly(N-salicylidene allyl amine) membrane was 2.6 × 10⁻³ cm³(STP)cm/cm² cm Hg sec (barrer), and the selectivity toward oxygen was 2.2. As Co(II) was introduced into this membrane, oxygen permeability and oxygen selectivity increased to 2.82 × 10⁻² barrer and 8.5, respectively. The permeability and selectivity of Mn(II) chelate membrane were 3.28 × 10⁻² and 5, respectively. A major reason for the increased selectivity was the enhanced solubility of oxygen in chelate membrane upon chelation. The transport behavior of chelate membranes followed a dual-mode transport, and the parameters were estimated and compared between Co(II) and Mn(II) membranes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 483–490, 1997     

Gamma‐radiation‐induced graft copolymerization of N‐[4‐(N′‐substituted amino carbonyl)phenyl] maleimide onto poly(vinlyl chloride) films

Three types of N[4‐(N‐substituted amino carbonyl)phenyl] maleimide (RPhMI:N‐substituent (R) = phenyl, cyclohexyl, p‐chlorophenyl) were grafted onto poly(vinyl chloride) (PVC) films by using gamma irradiation. The effects of different parameters on the graft yield were investigated. These parameters included radiation dose and monomer concentration. Thermal properties of the grafted polymer were investigated by the determination of dehydrochlorination rate, thermal gravimetric behavior, and UV stability.     

Gas transport in poly(vinyl cyclohexanecarboxylate)

Low-pressure gas permeation measurements were performed on poly(vinyl cyclohexanecarboxylate) to evaluate its transport characteristics. The transport data of CO₂, O₂, N₂, He, and Ar, were presented as a function of temperature ranging from 15 to 85°C. The apparent transport parameters were determined by the time lag method above and below the glass transition temperature and they were compared with other polymers of similar chemical structures. The side chain of the polymer has a bulky cyclohexyl group, which seemed to increase gas diffusivity. The activation energy for diffusion seemed to be related with the polarity of side chain. The relationships between gas diffusivity, physical properties, and chemical structure were qualitatively discussed in comparison with the data on poly(vinyl benzoate) and poly(vinyl acetate).     

Separability of SO2 from SO2/N2 mixture through sulfoxide-modified poly(vinyl alcohol) and cellulose membranes

Separability of SO₂ from mixtures of SO₂ and N₂ gases was studied for membranes of poly(vinyl alcohol) (PVA) and cellulose modified with methyl, ethyl, t-butyl, and phenyl vinyl sulfoxides. Of these sulfoxide-modified polymers, the phenyl vinyl sulfoxide-modified PVA membranes were found to give the best separation of SO₂. In the phenyl vinyl sulfoxide modified PVA membranes, the permeability coefficient of SO₂ increased with sulfoxide content while separability of SO₂ was maximum at a sulfoxide content of 23.5 mol %; the separation factor of SO₂ was about 170 at this sulfoxide content. © 1993 John Wiley & Sons, Inc.     

Synthesis of Novel C<Subscript>60</Subscript>-containing Polymers Based on Poly(vinyl phenol) and Their Photo-transformation Properties

Summary Nitroxide-terminated poly(p-tert-butoxystyrene), poly(p-acetoxystyrene), and poly(p-tert-butoxycarbonyloxystyrene) were synthesized by a living radical polymerization technique. C₆₀-bearing polymers were obtained by the reaction of C₆₀ with nitroxide-terminated polymers. Transformation of the precursor polymers into C₆₀-bearing poly(vinyl phenol) was carried out by UV (254 nm) irradiation of the films of the C₆₀-bearing precursor polymers in the presence of a photoacid generator and followed by post-exposure baking. The transformation was confirmed by the appearance of O-H stretching in IR spectra. C₆₀-bearing poly(vinyl phenol) showed the some solubility in solvents as observed for poly(vinyl phenol). This revised version was published online mid-November 2004. Unfortunately, an earlier version was originally published by mistake.     

Fundamental salt and water transport properties in directly copolymerized disulfonated poly(arylene ether sulfone) random copolymers

Water and sodium chloride solubility, diffusivity and permeability in disulfonated poly(arylene ether sulfone) (BPS) copolymers were measured for both acid and salt form samples at sulfonation levels from 20 to 40 mol percent. The hydrophilicity of these materials, based on water uptake, increased significantly as sulfonation level increased. The water permeability of BPS materials in both the salt and acid forms increases more than one order of magnitude as sulfonation level increases from 20% to 40%, while NaCl permeability increases by two orders of magnitude. The water and salt diffusivity and permeability were correlated with water uptake, consistent with expectations from free volume theory. In addition, a tradeoff was observed between water/salt solubility, diffusivity, and permeability selectivity and water solubility, diffusivity and permeability, respectively. This finding suggests a water/salt permeability/selectivity tradeoff, similar to that operative in gas separation polymers, in this family of polymers.     

Sorption, diffusion, and permeation of light olefins in poly(ether block amide) membranes

Sorption, diffusion, and permeation of three olefins (i.e., C₂H₄, C₃H₆, and C₄H₈) in poly(ether block amide) (PEBA 2533) membranes at different temperatures and pressures were investigated. This is pertinent to olefin recovery from resin off gas in polyolefin manufacturing. The relative contribution of solubility and diffusivity to the preferential permeability of olefins over nitrogen was elucidated. It was revealed that the favorable olefin/nitrogen permselectivity was primarily attributed to the solubility selectivity, whereas the diffusivity selectivity may affect the permselectivity negatively or positively, depending on the operating temperature and pressure. The olefin permeability is in the order of C₄H₈>C₃H₆>C₂H₄, the same order as their solubility in the membrane. In general, a low temperature favors both the permeability and selectivity. With an increase in pressure and/or a decrease in temperature, the sorption uptake of the olefin in the membrane increases progressively, and the diffusivity and hence the permeability are also enhanced because of the increased membrane plasticization/swelling caused by the penetrant sorbed in the membrane. At a given temperature, the pressure dependence of solubility and permeability could be described empirically by an exponential function. The limiting solubility at infinite dilution was correlated with the reduced temperature, and the hypothetical diffusivity at zero pressure was related to temperature by the Arrhenius equation.     

Synthesis of block copolymers of poly(p-dioxanone) block poly(tetrahydrofuran)

Summary The triblock copolymers of poly(p-dioxanone)-b-poly(tetrahydrofuran)-b-poly(p-dioxanone) were synthesized by ring-opening polymerization of p-dioxanone in the presence of dihydroxyl poly(tetrahydrofuran)(PTHF) using stannous octoate (SnOct₂) as a catalyst. The effects of feed ratio, reaction time and reaction temperature on the copolymerization were investigated. It was found that the optimal reaction temperature and time were 80 °C and 42 hours, respectively, and the molar ratio of p-dioxanone/SnOct₂ (PDO/cat.) had little influence on the inherent viscosity of the copolymers. The triblock copolymers were characterized by various analytical techniques such as ¹H-NMR and DSC.     

Synthesis and Properties of Cross-Linked Poly(vinylene-arsine)

Summary Cross-linked poly(vinylene-arsine)s (4) were synthesized by a free-radical terpolymerization of phenylacetylene (2), hexaphenylcyclohexaarsine (l), and p- or m-diethynylbenzene (p- or m-3) at different compositions in the presence of a catalytic amount of AIBN. The number-average molecular weights of the resulting polymers were a few thousands estimated by gel permeation chromatography (GPC) analysis. By gas chromatography (GC) analysis p-3 was found to be more reactive during the polymerization than m-3 and the resulting cross-linked polymer (p-4) showed lower solubility than that of m-4. The cross-linked poly(vinylene-arsine)s showed higher glass transition temperature in the measurement of differential scanning calorimetry (DSC) and more red-shifted emission in chloroform solution than that of the linear poly(vinylene-arsine). These properties could be tuned by varying the monomer feed ratio.     

Role of specific interactions on fiber formation in the electrospinning of poly(vinyl phenol)/poly(vinyl pyrrolidone) blend solutions

The minimum concentration (C_i) required for electrospinning polymeric fibers from solutions of mixtures of poly(vinyl phenol) and poly(vinyl pyrrolidone) has been experimentally determined for different blend compositions. This minimum concentration C_i has its lowest value when the polymers are mixed in a 1/1 molar ratio. This article shows different results that seem to indicate that the strong hydrogen bonding interactions between the two polymers and the corresponding higher apparent molecular weight cause the reduction of the C_i value. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Hydrophilic interpolymer membranes from crosslinked blends of poly(vinylalcohol), poly(styrene sodium sulfonate) and poly(vinyl methyl ether–alt–maleic anhydride)

Interpolymer ion exchange membranes were prepared from a compatible casting solution that contained poly(styrene sodium sulfonate), poly(vinyl methyl ether–alt–maleic anhydride), and poly(vinyl alcohol). Crosslinking of the films was accomplished through the formation of ester linkages that were stable in aqueous environments. Membrane properties (water content, capacity, concentration potential, equivalent conductivity) were measured over a wide range of membrane compositions. Ultrafiltration was carried out with a feed solution that was 0.01N in KCI and 15 ppm in erythrosin. Rejection and hydraulic permeability data were reported as a function of membrane composition.     

Carbon molecular sieve membranes derived from trimethylsilyl substituted poly(phenylene oxide) for gas separation

Carbon molecular sieve membranes for gas separation prepared using poly(phenylene oxide) (PPO) as precursor have been examined. The PPO precursor was modified by introducing a trimethylsilyl (TMS) substituent and its effect on the gas transport property of the resulting carbon membrane was examined. TMS-substituted PPO (TMSPPO) was prepared in a high yield by a simple one-step reaction, and its carbon membrane was successfully fabricated. The modification improved the gas permeability of the resulting membrane which also exhibited excellent O₂/N₂ and CO₂/CH₄ separation performance comparable to those of polyimide-derived carbon membranes. From the analysis of the microstructure of the TMSPPO carbon membranes, it is believed that the TMS groups improve gas diffusivity by increasing the micropore volume.     

Miscibility in poly(vinyl chloride)/chlorinated poly(vinyl chloride) blends,and blends of different chlorinated poly(vinyl chlorides)

Blends of poly(vinyl chloride) with chlorinated poly(vinyl chloride) (PVC), and blends of different chlorinated poly(vinyl chlorides) (CPVC) provide an opportunity to examine systematically the effect that small changes in chemical structure have on polymer-polymer miscibility. Phase diagrams of PVC/CPVC blends have been determined for CPVC's containing 62 to 38 percent chlorine. The characteristics of binary blends of CPVC's of different chlorine contents have also been examined using differential calorimetry (DSC) and transmission electron microscopy. Their mutual solubility has been found to be very sensitive to their differences in mole percent CCl₂ groups and degree of chlorination. In metastable binary blends of CPVC's possessing single glass transition temperatures (T_g) the rate of phase separation, as followed by DSC, was found to be relatively slow at temperatures 45 to 65° above the T_g of the blend.     

Gravimetric and volumetric study of the sorption of gases and vapors in poly(vinyl chloride) powders

The sorption of a variety of gases and organic vapors in poly(vinyl chloride) (PVC) powders has been studied gravimetrically with a recording microbalance and volumetrically with a gas pycnometer and an automatic surface area analyzer. For nitrogen, carbondioxide, vinyl chloride, methanol, acetone, n-butane, and benzene at low penetrant activities and temperatures below T_g, sorption isotherms exhibit the downward curvature characteristic of dual-mode sorption. The solubility of each of these penetrants is lower in heat-treated PVC samples than in samples recovered from the polymerization without additional heating. It has been possible to estimate the parameters of the dual-mode sorption model for carbondioxide, vinyl chloride, and methanol. The results indicate that the history-dependence of gas or vapor solubility is associated only with the “hole-filling” term of the dual-mode model; the normal dissolution or Henry's Law term is essentially unaffected by the prior heat treatment of the PVC.     

Gas permeation properties of poly(2,5‐benzimidazole) derivative membranes

In this article, three novel polymers based on poly(2,5‐benzimidazole) (ABPBI) were synthesized by introducing propyl, isobutyl or n‐butyl groups to its side chain through an alkyl substitution reaction. FTIR and ¹³C NMR were applied to confirm the formation of corresponding chemical groups. Their physical properties including crystallinity, thermal stability, mechanical strength, and micro‐morphology were also characterized. Their solubility in common solvents were also tested to see if the modification will bring any improvement. Gas permeation properties of three derivative membranes prepared by a casting and solvent‐evaporation method were tested with pure gases including H₂, N₂, O_2, CH₄, and CO₂. It has been revealed that gas with a smaller molecular size owned a larger permeability. This means gas permeation in all prepared membranes should be diffusivity selective. Among all three modified ABPBI membranes, isobutyl substitution modified ABPBI (IBABPBI) showed the best selectivity of H₂ over other gases such as N₂ (～185) and CO₂ (～6.3) with a comparable permeability (～9.33 barrer) when tested at 35°C and 3.0 atm. Testing temperature increase facilitated gas permeation for all three membranes obviously; while in term of gas selectivity temperature increase showed diverse alteration because it brought variable impact on gas solubility of different gases. Even so, IBABPBI membrane still owned acceptable selectivity of H₂ over N₂ (～118) and CO₂ (～6.3) with an almost doubled permeability (～17.5 barrer) when tested at 75°C and 3.0 atm. Additional tests showed that running at high pressure did not bring any obvious deterioration to gas separation performance of IBABPBI membrane. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40440.     

Permeability of polyimides derived from non-coplanar diamines and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride

A series of polyimides including a non-coplanar moiety were synthesized in order to investigate the effect on gas permeability and selectivity. The gas permeation properties of He, H₂, O₂, N₂, CH₄ and CO₂ were measured using a constant-volume method. Only 6FDA-terphenyl consisting of laterally attached phenyl groups shows a substantial increase because its terphenyl moiety is a rigid structure with a high aspect ratio. The order of permeability increase from 6FDA-phenyl to 6FDA-terphenyl is consistent with the calculated fraction free volume and measured permittivity. It is observed that the most gain in permeability for 6FDA-terphenyl polyimide arises from the enhancement in apparent diffusion coefficient, while the permeability increase for 6FDA-biphenyl is mainly due to the increase in solubility. A relationship of diffusivity vs. gas penetrant size as well as gas solubility vs. critical temperature of gas penetrant was also investigated.     

Gas Diffusion and Solubility in Poly(organophosphazenes): Results of Molecular Simulation Studies

A combination of quantum chemistry, molecular dynamics, and Monte Carlo methods have been used to investigate gas diffusion and solubility in three isomeric poly[di(butoxyphosphazenes)] and in amorphous and crystalline states of poly[bis(2,2,2-trifluoroethoxyphosphazene)] (PTFEP). In this review of recently published studies reported from our laboratory, conclusions are reached in regards to the relationship between polymer structure and gas diffusion and sorption in poly(organophosphazenes). These conclusions also serve to validate our current understanding of the nature of gas transport in other polymers. Specifically, gas diffusivity has been shown to increase with increasing side-chain and main-chain mobility as determined from vectorial autocorrelation function analysis; however, high diffusivity is accompanied by a loss in diffusive selectivity resulting in decreasing permselectivity with increasing permeability. Simulation of crystalline supercells of PTFEP indicate that gas diffusion is unrestricted in the crystalline state as has been reported only for a few other polymers, principally poly(4-methyl-1-pentene). Gas solubility in poly(organophosphazenes) correlates well with gas condensability as measured by the Lennard–Jones potential well depth parameter, ɛ/k. Exceptions are cases where specific interactions can occur between gas molecules and the polymer chain such as is the case of CO₂ and PTFEP. High-level ab initio calculations of the interaction of CO₂ with low-molecular-weight fluoroalkanes indicate the presence of a weak quadrupole–dipole interaction. Association of CO₂ with the trifluoromethyl groups of the trifluoroethoxy side chain of PTFEP has been confirmed by radial distribution function (RDF) analysis of MD trajectories. Comparison between solubility coefficients obtained from Grand Canonical Monte Carlo (GCMC) simulations of amorphous cells with experimental values of microcrystalline PTFEP indicates that gas solubility in polyphosphazenes such as PTFEP that exhibit a mesophase/crystalline state is greatly reduced. This paper is dedicated to Prof. Harry Allcock for his scientific contributions to inorganic and organometallic polymers.     

Synthesis and evaluation of some fatty esters as plasticizers and fungicides for poly(vinyl acetate) emulsion

n-Fatty alcohols (average molecular weight 187), prepared from n-paraffins, were treated with a series of dibasic acids such as malonic, succinic, glutaric, adipic and phthalic anhydride to give the corresponding fatty esters. The prepared fatty esters were formulated with poly(vinyl acetate) emulsion and used as films or textile coatings. Tests such as rate of drying, mechanical properties and resistance to micro-organisms were carried out. Samples of poly(vinyl acetate) plasticized with dibutyl phthalate were also prepared and evaluated for the purpose of comparison. The antifungal activity of these compounds was studied. The results obtained indicate that the prepared fatty esters can be used not only as plasticizers but also as fungicides and in some respects they are better than the conventional dibutyl phthalate plasticizer.