Simulation of experimentally observed dilation phenomena during integral gas sorption in glassy polymers

A molecular modeling investigation of dilation effects induced by sorbed gas molecules in two glassy polymers is presented. As experimental reference, integral sorption of CO₂ and CH₄ was measured for polysulfone (PSU) and a polyimide (6FDA‐TrMPD, PI4) at 308 K and a pressure of 10 bar. Simultaneously, the gas induced swelling effect was measured with a dilatometer based on a capacitive distance sensor recorded. The experimental evidence of the (on the observed time scale and concentration levels) elastic nature of the gas induced dilation is supported by the dilation and contraction behavior observed in molecular dynamics (MD) simulations of respective detailed atomistic packing models. These models were constructed in accordance with gas concentration levels obtained from the experimental sorption results. Quantitative deviations between simulated and measured dilations are discussed as a consequence of an anelastic response of the polymer matrix which is too fast to be resolved in the experiments whose kinetics is dominated by diffusional processes. In the simulation, the initial insertion of penetrant molecules into equilibrated packing models “circumvents” the slow diffusional process of the experiment and allows a reasonable representation of the dilation process as well as a closer investigation. Our simulation approach reveals a different behavior for PSU and PI4 on the corresponding time scale. Most likely, the different chain mobility of the two polymers is responsible for the respective response to the inserted amount of gas molecules which is discussed in terms of the different chain mobilities of the two polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 59–71, 2008     

Dilation of polyethylene by sorption of carbon dioxide

The dilation of low-density polyethylene accompanied by the sorption of CO₂ was measured by microscopy under pressures up to 50 atm at temperatures from 25 to 55°C. The dilatometry measurement, which is also applied to the determination of the thermal expansion coefficient, is directly performed by a cathetometer. The dilation of LDPE by sorbed CO₂ is linear with concentration. The buoyancy correction is described for the CO₂ sorption isotherms in LDPE. The partial molar volume of CO₂ in LDPE, calculated from the dilation and the sorption isotherms, is almost independent of temperature.     

High‐pressure sorption of carbon dioxide and methane in all‐aromatic poly(etherimide)‐based membranes

The sorption of compressed carbon dioxide and methane in a series of all‐aromatic poly(etherimide) (PEI) thin films is presented. The polymer films are derived from the reactions between an arylether diamine (P1) and four different dianhydrides [3,3′,4,4′‐oxydiphthalic dianhydride (ODPA), 3,3′,4,4′ biphenyltetra‐carboxylic dianhydride (BPDA), 3,3′,4,4′‐benzo‐phenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA)] that have been selected to systematically change the flexibility of the polymer backbone, the segmental mobility, and the nonequilibrium excess free volume (EFV) of the polymer. The EFV, gas sorption capacities, and sorption‐ and temperature‐induced dynamic changes in film thickness and refractive index have been investigated by spectroscopic ellipsometry. The sorption capacity depends to a great extent on the PEI backbone composition. PMDA‐P1 shows the highest carbon dioxide sorption, combined with the lowest sorption selectivity because of the predominant sorption of methane in the EFV. For ODPA‐P1, the highest sorption selectivity is obtained, while it shows little long‐term relaxations at carbon dioxide pressures up to 25 bar. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 986–993     

Sorption of carbon dioxide in fluorinated poyimides

Sorption isotherms of CO₂ for ten fluorinated polyimides measured at 35°C and up to about 25 atm are analyzed according to the dual-mode sorption model. Sorption properties for these polyimides are compared with those for other glassy Polymers including unfluorinated polyimides. The glassy polymers with higher glass transition temperatures T_g tend to show greater CO₂ sorption. Introduction of a ? C (CF₃)₂? linkage into the repeat unit of the main chain increases the sorption by 20–80%. For glassy polymers, including the fluorinated and unfluorinated polyimides, the Langmuir affinity constant b and Henry's law solubility constant k_D are correlated with the content of functional (carbonyl or sulfonyl) groups [FG], and composite parameter reflecting the magnitude of both [FG] and free-space fraction V_F, respectively, with some exceptions. The Langmuir capacity constant C′_H is correlated with T_g, but there are two correlation lines; one for unfluorinated polyimides and a different one for other glassy polymers including fluorinated polyimides. The slope of the former group is smaller probably because of smaller differences in thermal probably because of smaller differences in thermal expansion coefficients in rubbery and glassy states. Most fluorinated polyimides show greater solubility of CO₂ than unfluorinated polyimides and other glassy polymers, because of their larger C′_H and k_D. © 1993 John Wiley & Sons, Inc.     

Lowering the dielectric constant of polyimide thin films by swelling with supercritical carbon dioxide

The swelling with supercritical carbon dioxide (sc‐CO₂) of thin films of polyimides having various structures was investigated. It was shown that the degree of swelling is significantly influenced by the solvent which was used for the synthesis of those polyimides, by the solvent which was used for the preparation of thin films and by the conformational rigidity of the polymers. The presence of hexafluoroisopropylidene groups in the main chain of a polymer prevents its swelling with sc‐CO₂. The best results were obtained for polyimide film ULTEM, based on m‐phenylene‐diamine and isopropylidene‐diphenoxy‐bis(phthalic anhydride), synthesized in benzoic acid, whose free volume increased twice and its dielectric constant decreased from 3.15 to 2.45 by swelling with sc‐CO₂. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and characterization of some novel aromatic polyimides

Three new diamines 1,2-di(p-aminophenyloxy)ethylene, 2-(4-aminophenoxy)methyl-5-aminobenzimidazole and 4,4-(aminopheyloxy) phenyl-4-aminobenzamide were synthesized and polymerized with 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BP), 4,4′-(hexafluoroisopropyledene)diphthalic anhydride (HF) and 3,4,9,10-perylene tetracarboxylic acid dianhydride (PD) either by one step solution polymerization reaction or by two step procedure. The later includes ring opening poly-addition to give poly(amic acid), followed by cyclodehydration to polyimides with the inherent viscosities 0.62-0.97 dl/g. Majority of polymers are found to be soluble in most of the organic solvents such as DMSO, DMF, DMAc, m-cresol even at room temperature and few becomes soluble on heating. The degradation temperature of the resultant polymers falls in the ranges from 240 °C to 550 °C in nitrogen (with only 10% weight loss). Specific heat capacity at 300 °C ranges from 1.1899 to 5.2541 J g⁻¹ k⁻¹. The maximum degradation temperature ranges from 250 to 620 °C. T_g values of the polyimides ranged from 168 to 254 °C.     

Dilation of polycarbonate by carbon dioxide

A new technique is described for dilatometry under high pressure. The technique is based on optical interferometry and is analogous to measuring the thickness of thin, nonabsorbing films and coatings. The procedure is demonstrated for the well-characterized system of n-pentane sorption by polyisobutylene, and then results for the dilation of polycarbonate by the sorption of carbon dioxide are presented. The dilation of polycarbonate by CO₂ is nearly linear with concentration; the partial molar volume of CO₂ decreases slightly with increasing pressure. This result indicates that all sorbed CO₂ molecules contribute equally to the dilation of the polymer matrix and that none reside in microvoids or in preexisting free-volume elements which do not contribute to volume expansion of the polymer.     

Polyhydroxybutyrate production from carbon dioxide by cyanobacteria

Genetic characterization and enhancement of polyhydroxybutyrate (PHB) accumulation in cyanobacteria were investigated for efficient PHB production from CO₂. The genome DNAs in the PHB-accumulating strains Synechococcus sp. MA19 and Spirulina platensis NIES46 retained the highly homologous region to phaC of Synechocystis PCC6803, whereas low homology was detected in the nonaccumulating strains Synechococcus sp. PCC7942 and Anabaenacylindrica NIES19. Synechococcus sp. MA19, which accumulates PHB up to 30% of dry cell weight from CO₂ as the sole carbon source, was mutated by insertion of transposon Tn5 to enhance the PHB accumulation. Genetic and physiological analysis of the mutant indicated that decreased phosphotransacetylase activity could trigger an increase of acetyl coenzyme A leading to enhancement of PHB accumulation. PHB synthase in Synechococcus sp. MA19 was probably attached to thylakoid membrane since PHB granules were associated with pigments. A genetically engineered cyanobacteria retaining soluble PHB synthase from Ralstonia eutropha accumulated pigment-free PHB granules, which is an advantage for the purification of PHB.     

Dilation of poly[1-(trimethylsilyl)-1-propyne] during sorption of n-nonane

The linear expansion and contraction in the principal planar directions of poly[1-(trimethylsilyl)-1-propyne] film were measured concurrently with the sorption of n-nonane at 35°C. After the first sorption cycle, in which the polymer exhibited markedly nonisotropic volumetric dilation, the polymer expanded and contracted reproducibly during subsequent multiple sorption and desorption cycles. These reversible dilation isotherms were reproducible from sample to sample. The fractional change in length was identical in arbitrarily selected, orthogonal directions in the plane of the film, suggesting that the expansion and dilation of the sample are isotropic. When plotted versus the activity of n-nonane, the linear expansions in the plane of the film are slightly concave to the activity axis, reaching levels over 10% at the highest activities. The experimental partial specific volume of the polymer is near its pure component value but that of the penetrant is much less than its pure component value. Moreover, the magnitude of dilation observed is described rather closely by the dilation which would result solely from the Henry's law portion of sorption, assuming zero volume-change of mixing. These results are consistent with the explicit notions of “hole-filling” associated with the Langmuir mode in the dual-mode model. © 1993 John Wiley & Sons, Inc.     

低活性无烟煤固定床二氧化碳催化气化反应动力学研究

在内径18 mm的固定床反应器中研究了福建低活性无烟煤二氧化碳催化气化反应动力学。考察了消除内外扩散影响的实验条件。在750 ℃～907 ℃，以碳酸钠为催化剂分别测定了永安丰海筛无烟煤、永安加福筛无烟煤和永定无烟煤的转化率与时间的关系；以碳酸钾及纸浆黑液为催化剂测定了永定无烟煤的转化率与时间的关系。永安加福筛无烟煤采用均相一级反应模型及未反应缩芯模型进行拟合，得出气化反应速率常数、反应活化能和指前因子，与热天平的实验结果进行比较，固定床反应速率常数明显变大，活化能和指前因子也大，是由于固定床中有较高的二氧化碳到煤粒表面的传递速率和较高的升温速率所致。     

Unexpected selective enhancement of the thermal stability of aromatic polyimide materials by cerium dioxide nanoparticles

The unusual effect of selective enhancement of the thermal stability of aromatic polyimide materials was established through the introduction of cerium dioxide nanoparticles into these polymers as nanofiller. Depending on the chemical structure of the polymers, a marked increase or a substantial decrease in the thermal stability of the nanocomposite material was registered by thermal analysis, as compared with that of unfilled polymer material. The positive effect was registered only for the composite materials based on the matrix polyimides containing the sulfur atoms located in the sulfonic groups arranged in the elementary units. The results of the thermogravimetric examination are compared with the data obtained during the mechanical tests of the same samples. The possible reasons for the alteration of the thermal stability of polymers by ceria nanoparticles are discussed. The effect above can be of substantial practical interest providing new options for the design of polyimide nanocomposite materials with enhanced thermal stability.     

Transport of carbon dioxide and methane in glassy aromatic polyesters

Solubilities and diffusivities of CO₂ and CH₄ in two aromatic polyesters [Ardel® poly(bisphenol A phthalate) (PAr) and poly(phenolphthalein phthalate) (PPha)] and one polycarbonate [Lexan® (PC)], generated from independent sorption and permeation measurements at 35°C and up to 25 atm, are compared. The permeability ratio for CO₂ over CH₄, at 20 atm and 35°C, ranges from 24 for PC, to 21 for PAr, and 27 for PPha. However, the permeability of PPha and PAr are 40 and 120% higher, respectively, than that of PC. Less than 21% change in the gas diffusivity was observed; therefore, a major portion of the observed higher permeability of PPha and PAr is attributed to an increase in the gas solubility. These data are interpreted qualitatively in terms of changes in the calculated packing density, chain torsional mobility of the polymer, and gas-polymer attraction.     

Synthesis and characterization of organosoluble ditrifluoromethylated aromatic polyimides

Two novel diamine monomers, 1,4‐bis (4‐aminophenoxy)‐2‐[(3′,5′‐ditrifluoromethyl)phenyl]benzene and 1,4‐bis [2′‐cyano‐3′(4″‐amino phenoxy)phenoxy]‐2‐[(3′,5′‐ditrifluoromethyl)phenyl] benzene, were synthesized from (3,5‐ditrifluoromethyl)phenylhydroquinone. A series of ditrifluoromethylated aromatic polyimides derived from the diamines were prepared through a typical two‐step polymerization method. These polyimides had a high thermal stability, and the temperatures at 10% weight loss were above 507 °C in nitrogen. Most of the polymers showed good solubility in anhydrated 1‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, chloroform, and tetrahydrofuran at room temperature. All the polymers formed transparent, strong, and flexible films with tensile strengths of 63.6–95.8 MPa, elongations at break of 5–10%, and Young's moduli of 2.38–2.96 GPa. The dielectric constants estimated from the average refractive indices are 2.69–2.89. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3018–3029, 2005     

Interaction of carbon dioxide with ditoluenetitanium

The interaction of ditoluenetitanium with CO{in2} has been studied. Based on hydrolysis, thermolysis, and IR spectral data, the conclusion is drawn that a low-valent titanium oxalate is formed.This study was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-5538).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2241–2242, December, 1994.     

Infrared spectroscopic studies of CO2 sorbed in glassy and rubbery polymeric membranes

Infrared spectra of CO₂ sorbed in rubbery and glassy polymers were measured to examine the relationships between the spectroscopic data and physical properties of the polymeric membranes. The “V-shape” tendency in the plot of W₁ [i.e., half-width of CO₂ peak sorbed in the membranes] vs glass-transition temperature (T_g) is observed, and has exactly the same tendency that is widely known from the plot of log D (diffusion coefficient) vs T_g. It is suggested that the membranes having a wider W₁ give a faster diffusion coefficient, since W₁ is inversely related to the moment of inertia of CO₂ in the membranes. Two distinct peaks of CO₂ were not observed in the infrared spectra of CO₂ sorbed in the glassy polymers. This suggests that the states of CO₂ in the Henry mode and Langmuir mode in the glassy polymers are similar in the spectroscopic measurements. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of new soluble aromatic polyimides from diaminotetraphenylimidazolinone and aromatic tetracarboxylic dianhydrides

A series of new soluble aromatic polyimides with inherent viscosities of 0.65–1.12 dL/g were synthesized from 1,3-bis(4-aminophenyl)-4,5-diphenylimidazolin-2-one and various aromatic tetracarboxylic dianhydrides by the conventional two-step procedure that included ring-opening polyaddition and subsequent thermal cyclodehydration. These polyimides could also be prepared by the one-pot procedure in homogeneous m-cresol solution. Most of the tetraphenyl-pendant polyimides were soluble in organic solvents such as N,N-dimethylacetamide, 1,3-dimethyl-2-imidazolidone, and m-cresol. Some polyimides gave transparent, flexible, and tough films with good tensile properties. The glass transition temperatures and 10% weight loss temperatures under nitrogen of the polyimides were in the range of 287–326 and 520–580°C, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1767–1772, 1998     

Hydrocarbon solubility,permeability, and competitive sorption effects in polymer of intrinsic microporosity (PIM‐1) membranes

The sorption and permeation of pentane, hexane, and toluene through highly permeable polymer of intrinsic microporosity (PIM‐1) membranes were investigated. It was established that the hydrocarbons sorbed strongly within the micro‐void regions of the PIM‐1 membrane. The sorption concentration was similar for the paraffins, pentane and hexane, but greater for aromatic toluene at high vapor activities. The magnitude of the hydrocarbon permeability was associated with the critical temperature of the hydrocarbon. The PIM‐1 membrane displayed selectivity for the three hydrocarbons over CO₂. As a consequence, the presence of the three hydrocarbons dramatically reduced the permeability of CO₂ and N₂ under mixed gas–vapor conditions to 68%–95% below the dry gas value. For all three hydrocarbons the N₂ permeability was more strongly impacted than CO₂ permeability, and hence the ideal CO₂/N₂ selectivity of PIM‐1 increased. It was determined that CO₂ and N₂ solubility decreased because of hydrocarbon competitive sorption while CO₂ and N₂ diffusivity also decreased because of anti‐plasticization, which was due to the presence of hydrocarbon clusters within the membrane structure. There was a clear correlation between the magnitude of anti‐plasticization and the critical temperature of the hydrocarbon. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 397–404