Towards predicting the solubility of CO2 and N2 in different polymers using a quasi-SMILES based QSPR approach

The solubility of gases in various polymers plays an important role for the design of new polymeric materials. Quantitative structure–property relationship (QSPR) models were designed to predict the solubility of gases such as CO₂ and N₂ in polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl acetate (PVA) and poly (butylene succinate) (PBS) at different temperatures and pressures by using quasi-SMILES codes. The dataset of 315 systems was split randomly into training, calibration and validation sets; random split 1 led to 214 training (r² = 0.870 and RMSE = 0.019), 51 calibration (r² = 0.858 and RMSE = 0.020) and 50 validation (r² = 0.869 and RMSE = 0.017) sets. The suggested approach based on the quasi-SMILES, which are analogues of the traditional SMILES gives reasonable good predictions for solubility of CO₂ and N₂ in different polymers. The described methodology is universal for situations where the aim is to predict the response of an eclectic system upon a variety of physicochemical and/or biochemical conditions.     

Differential Kinetic Spectrophotometric Determination of Methamidophos and Fenitrothion in Water and Food Samples by Use of Chemometrics

A spectrophotometric method for simultaneous analysis of methamidophos and fenitrothion was proposed by application of chemometrics to the spectral kinetic data, which was based upon the difference in the inhibitory effect of the two pesticides on acetylcholinesterase (AChE) and the use of 5,5′‐dithiobis(2‐nitrobenzoic acid) (DTNB) as a chromogenic reagent for the thiocholine iodide (TChI) released from the acetylthiocholine iodide (ATChI) substrate. The absorbance of the chromogenic product was measured at 412 nm. The different experimental conditions affecting the development and stability of the chromogenic product were carefully studied and optimized. Linear calibration graphs were obtained in the concentration range of 0.5–7.5 ng·mL^?1 and 5–75 ng·mL^?1 for methamidophos and fenitrothion, respectively. Synthetic mixtures of the two pesticides were analysed, and the data obtained processed by chemometrics, such as partial least square (PLS), principal component regression (PCR), back propagation‐artificial neural network (BP‐ANN), radial basis function‐artificial neural network (RBF‐ANN) and principal component‐radial basis function‐artificial neural network (PC‐RBF‐ANN). The results show that the RBF‐ANN gives the lowest prediction errors of the five chemometric methods. Following the validation of the proposed method, it was applied to the determination of the pesticides in several commercial fruit and vegetable samples; and the standard addition method yielded satisfactory recoveries.     

The influence of different fillers on mechanical and physical properties of high-molecular-weight biodegradable aliphatic polyesters

Poly(ethylene succinate) and poly(butylene succinate) are synthetic biodegradable polymers, and much attention is paid to study the properties of pure polymers and the polymers modified by different comonomers and filling materials. The literature data on the physical properties of these polymers vary widely depending on their method of preparation and subsequent modifications. Most of the studies deal with low- and moderate-molecular-weight polymers or commercial grade polymers, modified by different comonomers and chain-extension agents. The data on pure high-molecular-weight polymers are scarce. In this work, we have prepared high-molecular-weight (MW range of (1.4–1.8) × 10⁵) poly(ethylene succinate) and poly(butylene succinate) by direct polycondensation at 200°C in a nitrogen flow without chain-extension agents. We have further studied the properties of pure polymers and examined the effect of different fillers (carbon nanotubes, SiO₂, Aerosil®) on the mechanical and physical properties of these polymers. Because of high-molecular-weight, the polymers possess increased tensile and storage moduli and thermostability. Even very low filler contents (up to 1 wt %) have a pronounced influence on the polymer properties: the polymer tensile and the storage modulus increases, the elongation at break decreases, and the thermal stability of the polymers decreases slightly. The effects of fillers are less pronounced compared with those for low- and moderate-molecular-weight polymers. When mixed together, poly(ethylene succinate) and poly(butylene succinate) crystallize independently from each other as evident from the mechanical and thermal analysis data.     

Neural networks for predicting air gap membrane distillation performance

The hollow fiber air gap membrane distillation (AGMD) has recently attracted tremendous attention for desalination and wastewater treatment due to its high packing density, low conductive heat loss, and latent heat recovery capability. Utilizing fast and accurate modeling tools to predict MD performance can result in the further development of desalination technologies. However, simple and time-saving prediction models to assess the AGMD performance were not abundant. Herein, AGMD performance, including permeate flux (J) and gained output ratio (GOR) was predicted through multiple linear regression (MLR) model, back propagation neural network (BP ANN) and radial basis function neural network (RBF ANN) under different hot temperatures (T_h), coolant temperatures (T_c), feed flow rates (F), and feed concentration (c). A total of 30 sets of data were used to train the proposed models, the other 10 external validation datasets not used for training the models were applied to validate the prediction accuracy. The results depicted that RBF ANN (SPREAD = 30, N = 30) showed greatest prediction performance (R² = 0.99–1) compared with BP ANN and MLR models (R² = 0.98–0.99; R² = 0.89–0.97). The computing time consumption of RBF ANN was higher than BP ANN. According to the Mean impact value (MIV) analysis, T_h had the strongest effect on J and GOR. Increasing T_h and decreasing c both had positive impacts on J and GOR, but increasing T_c or F resulted in a trade-off influence. A genetic algorithm (GA) was employed to optimize J and GOR simultaneously, the optimum J and GOR could reach 6.00 kg/m²·h and 7.70 respectively. In this study, the three prediction models proved their abilities to predict AGMD performance and further provide guidance in the actual membrane distillation water treatment process.     

High‐Performance Polymers for Membrane CO2/N2 Separation

This Concept examines strategies to design advanced polymers with high CO₂ permeability and high CO₂/N₂ selectivity, which are the key to the success of membrane technology for CO₂ capture from fossil fuel‐fired power plants. Specifically, polymers with enhanced CO₂ solubility and thus CO₂/N₂ selectivity are designed by incorporating CO₂‐philic groups in polymers such as poly(ethylene oxide)‐containing polymers and poly(ionic liquids); polymers with enhanced CO₂ diffusivity and thus CO₂ permeability are designed with contorted rigid polymer chains to obtain high free volume, such as polymers with intrinsic microporosity and thermally rearranged polymers. The underlying rationales for materials design are discussed and polymers with promising CO₂/N₂ separation properties for CO₂ capture from flue gas are highlighted.     

Evaluation of gas sorption parameters and prediction of sorption isotherms in glassy polymers

A model of continuous‐site distribution for gas sorption in glassy polymers is examined with sorption data of CO₂ and Ar in polycarbonate. A procedure is presented for determining from a measured isotherm the number of sorption sites in a polymer, an important parameter that previously had to be assumed. With this parameter value and solubility data obtained at zero pressure, the model can reasonably predict sorption isotherms of CO₂ in glassy polycarbonate for a wide temperature range. The number of sorption sites and the average site volume evaluated from CO₂ sorption isotherms are employed for the prediction of Ar sorption isotherms with zero‐pressure solubility data and the independently measured partial molar volume of Ar. A reasonable fit to the measured isotherms of Ar is achieved. With the proposed procedure, the continuous‐site model shows several advantages over the conventional dual‐mode sorption model. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 883–888, 2000     

Gas sorption and characterization of poly(ether‐b‐amide) segmented block copolymers

The solubilities of He, H₂, N₂, O₂, CO₂, CH₄, C₂H₆, C₃H₈, and n‐C₄H₁₀ were determined at 35°C and pressures up to 27 atmospheres in a systematic series of phase separated polyether–polyamide segmented block copolymers containing either poly(ethylene oxide) [PEO] or poly(tetramethylene oxide) [PTMEO] as the rubbery polyether phase and nylon 6 [PA6] or nylon 12 [PA12] as the hard polyamide phase. Sorption isotherms are linear for the least soluble gases (He, H₂, N₂, O₂, and CH₄), convex to the pressure axis for more soluble penetrants (CO₂, C₃H₈, and n‐C₄H₁₀) and slightly concave to the pressure axis for ethane. These polymers exhibit high CO₂/N₂ and CO₂/H₂ solubility selectivity. This property appears to derive mainly from high carbon dioxide solubility, which is ascribed to the strong affinity of the polar ether linkages for CO₂. As the amount of the polyether phase in the copolymers increases, gas solubility increases. The solubility of all gases is higher in polymers with less polar constituents, PTMEO and PA12, than in polymers with more polar PEO and PA6 units. CO₂/N₂ and CO₂/H₂ solubility selectivity, however, are higher in polymers with higher concentrations of polar repeat units. The sorption data are complemented with physical characterization (differential scanning calorimetry, elemental analysis, and wide angle X‐ray diffraction) of the various block copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2463–2475, 1999     

Exploring amino acid‐tethered polymethacrylates as CO2‐sensitive macromolecules: A concealed property

Carbon dioxide (CO₂)‐responsive polymers have been gaining considerable interest because of their reactions with CO₂, giving rise to gas‐switchable properties, which can easily be reversed by mild heating or purging with inert gases. Herein, the synthesis of a series of side‐chain amino acids (alanine, leucine, isoleucine, phenylalanine, tryptophan) appending poly(meth)acrylates carrying primary amine (? NH₂) groups via reversible addition‐fragmentation chain transfer (RAFT) polymerization method was reported. It was found that alanine, leucine, isoleucine containing polymers displayed solubility–insolubility transition behavior and their associated property changes (solution transmittance, electrical conductivity, pH, zeta potential, and hydrodynamic diameter) in water upon alternate bubbling of CO₂/N₂ at room temperature. Among the three CO₂‐sensitive polymers only leucine based macromolecule was further chain extended with a thermoresponsive motif, di(ethylene glycol) methyl ether methacrylate (DEGMMA), via RAFT polymerization. CO₂‐tunable lower critical solution temperature and self‐assembling behavior of the diblock copolymer was carefully examined by UV–vis, ¹H NMR spectroscopy, dynamic light scattering (DLS), and field emission‐scanning electron microscopy (FE‐SEM) to establish dual thermo and gas‐tunable flip–flop micellizaion from the as‐synthesized block copolymer. Formation of polyammonium methacrylate bearing bicarbonate as counter anion is responsible for pendant primary amine containing polymer induced CO₂‐responsiveness. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2794–2803     

Effects of tertiary amines and quaternary ammonium halides in polysulfone on membrane gas separation properties

Polymers containing CO₂‐philic groups are of great interest for CO₂/light gas separation membranes because the affinity toward CO₂ can effectively increase CO₂ solubility and thus permeability. In this study, polysulfones (PSUs) modified with different degrees of benzyldimethylamine (DMA), benzyltrimethylammonium fluoride (TMAF), and benzyltrimethylammonium iodide (TMAI) were synthesized using sequential post‐functionalization reactions and investigated for CO₂/N₂ and CO₂/CH₄ separation. The physical properties of these polymers were studied, including density, fractional free volume, and glass transition temperature. In contrast to the conventional wisdom that tertiary amines exhibit an affinity toward CO₂, this study convincingly shows that the DMA substituent has a minimal impact on CO₂ solubility and CO₂/light gas solubility selectivity in PSUs under dry condition. On the other hand, incorporating TMAF and TMAI in PSU significantly increases CO₂ solubility. Particularly, introducing TMAI with a molar ratio of 1.07 relative to PSU repeating units increases CO₂/CH₄ solubility from 4.4 to 5.2, CO₂/CH₄ permeability selectivity from 21 to 45, and CO₂/N₂ permeability selectivity from 24 to 33 at 35 °C, while the CO₂ permeability decreases from 5.6 to 1.7 Barrers. The effect of these functional groups in PSUs on gas diffusivity and diffusivity selectivity can be satisfactorily described by the free volume model. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1239–1250     

Biobased poly(2,5‐furandimethylene succinate‐co‐butylene succinate) crosslinked by reversible Diels–Alder reaction

We synthesized biobased poly(2,5‐furandimethylene succinate‐co‐butylene succinate) [P(FS‐co‐BS)] copolymers by polycondensation of 2,5‐bis(hydroxymethyl)furan, 1,4‐butanediol, and succinic acid. These copolymers could be crosslinked to form network polymers by means of a reversible Diels–Alder reaction with bis‐maleimide. The thermal properties, mechanical properties, and healing abilities of the P(FS‐co‐BS)s and the network polymers were investigated. The mechanical properties of the network polymers depended on the comonomer composition of the P(FS‐co‐BS)s and the maleimide/furan ratio in the network polymers. Some of the copolymers exhibited healing ability at room temperature, and their healing efficiency was enhanced by solvent or heat. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 216–222     

Crystallization kinetics and morphology of biodegradable poly(butylene succinate‐co‐propylene succinate)s

The crystallization behavior of biodegradable poly(butylene succinate) and copolyesters poly(butylene succinate‐co‐propylene succinate)s (PBSPS) was investigated by using ¹H NMR, DSC and POM, respectively. Isothermal crystallization kinetics of the polyesters has been analyzed by the Avrami equation. The 2.2‐2.8 range of Avrami exponential n indicated that the crystallization mechanism was a heterogeneous nucleation with spherical growth geometry in the crystallization process of polyesters. Multiple melting peaks were observed during heating process after isothermal crystallization, and it could be explained by the melting and recrystallization model. PBSPS was identified to have the same crystal structure with that of PBS by using wide‐angle X‐ray diffraction (WAXD), suggesting that only BS unit crystallized while the PS unit was in an amorphous state. The crystal structure of polyesters was not affected by the crystallization temperatures, too. Besides the normal extinction crosses under the POM, the double‐banded extinction patterns with periodic distance along the radial direction were also observed in the spherulites of PBS and PBSPS. The morphology of spherulites strongly depended on the crystallization temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 420–428, 2007     

Synthesis and properties of hyperbranched poly(ether sulfone)s prepared by self‐polycondensation of novel AB2 monomer

Hyperbranched poly(ether sulfone)s were prepared by the self‐polycondensation of the novel AB₂ monomer, 4‐(3,5‐hydroxyphenoxy)‐4′‐fluorodiphenylsulfone. The high‐molecular‐weight polymers were isolated in good yields. The degree of branching (DB) of the resulting polymers was investigated by the preparation of dendritic and linear model compounds. The DB determined by gated decoupling ¹³C NMR measurements was in the range 0.17–0.41 and was dependent on the base used for the self‐polycondensation. It was found that cesium fluoride was an effective base to form the polymer having the DB of 0.41. The resulting hyperbranched poly(ether sulfone)s showed good solubility in organic solvents. The solubility and the glass transition temperature of the polymers were influenced by the terminal functional groups. The unique thermal crosslinking phenomenon was observed during the DSC measurements of the hydroxyl‐terminated hyperbranched poly(ether sulfone) under air condition. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Miscibility enhancement and formation of interpenetrating spherulites in ternary blends of crystalline polymers

Miscible blends of three crystalline polymers, namely poly(butylene succinate) (PBS), poly(ethylene succinate) (PES), and poly(oxyethylene) (POE), exhibited interpenetrating spherulites, where a spherulite of one component grows inside the spherulites of other components. PBS and PES were immiscible above the melting points, T_m, of these substances, while ternary blends with POE showed miscibility, which depended on the molecular weight of POE. PBS and PES exhibited the same spherulitic growth process as in a miscible binary blend when they were crystallized from a homogeneous ternary melt. Spherulites of PBS, which is the highest‐T_m component, filled the whole volume first when a miscible ternary blend was quenched below T_m of POE, the lowest‐T_m component. Then, the blends showed either two types of crystallization processes. One was successive nucleation and growth of PES and POE spherulites, that is, PES nucleated and developed spherulites inside the PBS spherulites and then POE spherulites grew inside the interlocked spherulites of PBS and PES. The other was simultaneous growth and the formation of interpenetrating spherulites of PES and POE inside the PBS spherulites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 706–711, 2010     

超临界CO2在聚合物中的溶解计算研究进展

本文以超临界CO2在聚合物中的溶解计算模型为例,综述了状态方程、经验方程和人工神经网络计算方法的实现原理、研究现状和优缺点;依据人工神经网络预测方法存在的问题,重点阐述基于混合智能方法的神经网络溶解计算模型;并对溶解计算研究进行了总结和展望。     

Chain extension of adipic acid and (or) succinic acid/butanediol polyesters with 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoylbiscaprolactamate combined chain extenders

This paper provided an easy and flexible method to synthesize high molecular weight polyesters by polycondensation and chain extension. Low molecular weight polybutylene adipate, polybutylene succinate, and poly(butylene succinate‐co‐butylene adipate) (PBSA) were synthesized through melt condensation polymerization from adipic acid and/or succinic acid with butanediol. The prepolyesters obtained had different amount of ? COOH and ? OH terminal groups. Chain extension of them was carried out at 180–240°C using 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoyl biscaprolactamate as combined chain extenders. The influencing factors of the chain extension were studied. At the optimal conditions, chain‐extended polybutylene adipate with M_n up to 39,100, polybutylene succinate with intrinsic viscosity of 0.99 dl/g, and PBSA with intrinsic viscosity from 0.73 to 0.81 dl/g were synthesized. The chain‐extended polyesters were characterized by IR spectrum, ¹H NMR spectrum, differential scanning calorimetry, thermogravimetric analysis (TGA), wide angle X‐ray scattering, and tensile test. The thermal analysis showed that chain extension often led to slight decrease of the regularity, the crystallinity, and the melting point. This deterioration of the properties is not harmful enough to impair their thermal properties and obstruct them from being used as biodegradable thermoplastics. The TGA showed that the chain‐extended polyesters were stable with initial decomposition temperature over 354.7°C. The tensile strength of the chain extended PBS and PBSAs with butylene adipate units less than 20 mol% was in the range of 18.95–31.22 MPa. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of a novel AB2 monomer and corresponding hyperbranched poly(arylene ether phosphine oxide)s

A novel AB₂ monomer, 4‐(fluorophenyl)‐4′,4″‐(bishydroxyphenyl) phosphine oxide, was synthesized. The monomer was successfully polymerized to a modest molecular weight with various catalysts, including K₂CO₃ and Cs₂CO₃/Mg(OH)₂. Hyperbranched polymers exhibited exceptionally high thermal stability and solubility in conventional polar organic solvents and basic water solutions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3736–3741, 2000     

Fabrication‐controlled morphology of poly(butylene succinate) nano‐microcellular foams by supercritical CO2

Poly(butylene succinate) urethane ionomer (PBSUIs) foams with nano‐microcellular morphology were fabricated using supercritical CO₂ (sc‐CO₂) at different parameters. Effect of urethane ionic group (UIG) content (ranged from 1% to 5%) on the rheology and crystallization of PBSUIs were evaluated by intrinsic, dynamic rheological, X‐ray diffraction, and differential scanning calorimetry measurements. The results show that the complex viscosity of PBSUIs vastly improved, while their intrinsic viscosity and crystallinity decreased. They also evidenced that CO₂ promoted the formation of crystallites in the amorphous and increased the X_c of PBSU and PBSUIs foams. Scanning electron microscope was employed to explore the influences of UIG content and foaming parameters on the morphologies of PBSUIs microcellular foams, and it revealed that UIG content was the dominated factor. The cell size and cell densities of PBSUIs microcellular foams were smaller than 5.0 micrometers and higher than 1.5 × 10¹⁰ cells/cm³, respectively, even foamed at diverse variations of foam temperature and pressure. Interestingly, PBSUIs with 3% and 5% UIG content achieved microcellular foams in nano‐cells, high‐stretched elliptical shape. The mechanism was ascribed that these PBSUIs with high melt viscosities could retard the CO₂ bubbles to merge during the foam process and induce the cells to stretch and orient in depressururization direction. This study proposed a novel method for fabricating PBS nano‐microcellular foams.     

Microcellular foaming of polylactide and poly(butylene adipate‐co‐terphathalate) blends and their CaCO3 reinforced nanocomposites using supercritical carbon dioxide

Foamed polylactide (PLA), PLA–PBAT (poly (butylene adipate‐co‐terphathalate)) blend and their composites with CaCO₃ were prepared in a batch process using supercritical carbon dioxide (CO₂) at 12 MPa and 45°C. The solubility of CO₂ and its diffusion patterns in different PLA samples was investigated. PLA systems had a relatively high CO₂ solubility related to the carboxyl groups. CO₂ desorption behaviors in PLA systems first followed the Fickian diffusion mechanism in short time and then decreased slowly to a plateau. The addition of both PBAT and CaCO₃ into PLA impeded the desorption of CO₂. In the presence of second phase PBAT, nanoparticles CaCO₃ and dissolved CO₂, the PLA crystallization behavior investigated by DSC technique was greatly changed. As the desorption time increased, the gas induced crystallinity slightly decreased in consequence of less CO₂ content in each system and thus less plasticization effect. The cell morphology of foamed PLA and PLA composites showed interesting microstructure patterns. The prepared pure PLA foam exhibits a typical bimodal structure because of the foaming in both the amorphous and crystalline zones. With PBAT and CaCO₃ into PLA, the composite foam presented significant increase in cell uniformity and cell density. With less CO₂ content in each PLA sample, the cell structure showed interesting variation. Pure PLA foam presented transition from bimodal structure to more uniform cell structure with decreased cell density. In contract, PLA–PBAT foam show unfoamed regions because of none CO₂ left in the separated PBAT phase. Copyright © 2016 John Wiley & Sons, Ltd.     

Gas transport properties of poly(ether‐b‐amide) segmented block copolymers

The permeation properties of H₂, N₂, and CO₂ were determined at 35 °C and pressures up to 15 atm in phase‐separated polyether‐b‐polyamide segmented block copolymers. These polymers contain poly(ethylene oxide) [PEO] or poly(tetramethylene oxide) [PTMEO] as the rubbery polyether phase and nylon‐6 [PA6] or nylon‐12 [PA12] as the hard polyamide phase. Extremely high values of polar (or quadrupolar)/nonpolar gas selectivities, coupled with high CO₂ permeability coefficients, were observed. CO₂/H₂ selectivities as high as 9.8 and CO₂/N₂ selectivities as high as 56 were obtained in polymers with CO₂ permeability coefficients of approximately 220 × 10⁻¹⁰ cm³(STP) cm/(cm² s cmHg). As the amount of polyether increases, permeability increases. Gas permeability is higher in polymers with less polar constituents, PTMEO and PA12, than in those containing the more polar PEO and PA6 units. CO₂/N₂ and CO₂/H₂ selectivities are higher in polymers with higher concentrations of polar groups. These high selectivity values derive from large solubility selectivities in favor of CO₂. Because CO₂ is larger than H₂ and has, therefore, a lower diffusion coefficient than H₂, the weak size‐sieving ability of the rubbery polyether phase, which is the locus of most of the gas permeation, also contributes to high CO₂/H₂ selectivity. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2051–2062, 2000