Microporous Polymeric Materials Research Articles

The Kinetics of Formation of Microporous Polytriazine in Diphenyl Sulfone.

This study highlights the value of nonisothermal kinetic methods in selecting temperature conditions for the isothermal preparation of microporous polymeric materials. A dicyanate ester is synthesized and the kinetics of its polymerization in diphenyl sulfone are studied by calorimetry under nonisothermal conditions. The kinetics are analyzed by a model-based approach, using the Kamal model, as well as by a model-free approach, using an advanced isoconversional method. Both approaches correctly predict the time to completion of polymerization at a given temperature. The material prepared independently at the predicted temperature is characterized by electron microscopy and CO2 adsorption measurements and is confirmed to possess a microporous structure with a multimodal distribution of micropores with two major maxima at ~0.5 and 0.8 nm.

Hybrid Microporous Polymeric Materials with Outstanding Permeability and Increased Gas Transport Stability: PTMSP Aging Prevention by Sorption of the Polymerization Catalyst on HCPS.

The influence of hyper-crosslinked polystyrene (HCPS) MacronetTM MN200 on the gas transport properties and aging of the highly permeable glassy polymer poly(1-trimethylsilyl-1-propyne) (PTMSP) was studied and analyzed in detail. The gas transport characteristics of dense PTMSP membranes containing 0–10.0 wt % HCPS were studied. It was shown that the introduction of a small amount of HCPS into the PTMSP matrix led to a 50–60% increase of the permeability coefficients of the material for light gases (N2, O2, CO2) and slowed down the deterioration of polymer transport properties over time. The lowest reduction in gas permeability coefficients (50–57%) was found for PTMSP containing HCPS 5.0 wt % after annealing at 100 °C for 300 h. It was found that HCPS sorbed residues of tantalum-based polymerization catalyst from PTMSP. In order to investigate the influence of catalysts on transport and physical properties of PTMSP, we purified the latter from the polymerization catalyst by addition of 5 wt % HCPS into polymer/chloroform solution. It was shown that sorption on HCPS allowed for almost complete removal of tantalum compounds from PTMSP. The membrane made of PTMSP purified by HCPS demonstrated more stable transport characteristics compared to the membrane made of the initial polymer. HCPS has a complex effect on the aging process of PTMSP. The introduction of HCPS into the polymer matrix not only slowed down the physical aging of PTMSP, but also reduced chemical aging due to removal of active reagents.

A functionalized metal organic framework-laden nanoporous polymer electrolyte for exceptionally stable lithium electrodeposition.

A nanoporous all-solid-state MOF-laden polymer electrolyte that is simply mediated by an electronic effect shows remarkably high lithium electrodeposition stability of hundreds of charge-discharge cycles and over 1500 operating hours, while maintaining a very small voltage polarization. This result is a significant improvement relative to conventional PEO and, when used in an all-solid-state battery (ASSB), this electrolyte enabled enhanced cycle life. This new all-solid-state electrolyte shows a promising rational design for the emerging microporous polymeric materials as novel SPEs in ASSBs.

Pd NPs Decorated on POPs as Recyclable Catalysts for the Synthesis of 2‐Oxazolidinones from Propargylic Amines via Atmospheric Cyclizative CO2 Incorporation

AbstractA novel approach has been taken for the synthesis of a microporous polymeric materials of BBA‐1 and BBA‐2 (benzene−benzylamine), which is a POP (porous organic polymer) with its excellent surface area determined by BET study, via Friedel‐Crafts alkylation of benzene and benzylamine (or 4‐methoxybenzylamine) by utilizing a cross‐linker (formaldehyde dimethyl acetal) and a promoter (anhydrous FeCl3). Pd NPs were decorated over BBA‐1 and modified BBA‐2 to generate the desired catalysts (Pd@BBA‐1 and Pd@BBA‐2 respectively). The characterizations of the synthesized nanomaterials have been conducted by FE‐SEM, wide‐angle powder XRDmethods, N2 adsorption/desorption studies and high resolution transmission electron microscopy (TEM). Pd NPs decorated porous polymers are described here to facilitate the carboxylative cyclization of several propargylamine derivatives leading to the corresponding desired products (2‐oxazolidinone) under the application of ambient conditions (0.1 MPa of CO2, DMSO, 40–80 °C, 30–60 mg nanocatalyst). The Pd NPs‐loaded POP is competitive with previously reported catalytic systems. These pure polymeric microporous catalytic systems exhibited outstanding catalytic performances for the generation of oxazolidinones from several propargylic amines in the absence of organic and inorganic bases through atmospheric cyclizative CO2 incorporation. The modified nanocatalyst (Pd@BBA‐2) displayed exceptional recycling efficiency for the generation of oxazolidinones up to five runs without any noticeable decay in the activity of Pd@BBA‐2.

Modeling Amorphous Microporous Polymers for CO2 Capture and Separations.

This review concentrates on the advances of atomistic molecular simulations to design and evaluate amorphous microporous polymeric materials for CO2 capture and separations. A description of atomistic molecular simulations is provided, including simulation techniques, structural generation approaches, relaxation and equilibration methodologies, and considerations needed for validation of simulated samples. The review provides general guidelines and a comprehensive update of the recent literature (since 2007) to promote the acceleration of the discovery and screening of amorphous microporous polymers for CO2 capture and separation processes.

A large deformation poroplasticity theory for microporous polymeric materials

A coupled theory accounting for fluid diffusion and large deformations of elastic-viscoplastic microporous polymeric materials is presented. The theory is intended to represent the coupled deformation–diffusion response of a material which at a microscopic scale consists of a porous polymeric skeleton and a freely moving fluid in a fully connected pore space. Potential applications of the theory include modeling the response of polymer microfiltration membranes, as well as modeling the response of several hydrated biological tissues which are microporous polymeric materials containing a high concentration of liquids.

Towards high water permeability in triazine-framework-based microporous membranes for dehydration of ethanol.

The microstructural evolution of a series of triazine framework-based microporous (TFM) membranes under different conditions has been explored in this work. The pristine TFM membrane is in situ fabricated in the course of polymer synthesis via a facile Brønsted-acid-catalyzed cyclotrimerizaiton reaction. The as-synthesized polymer exhibits a microporous network with high thermal stability. The free volume size of the TFM membranes gradually evolved from a unimodal distribution to a bimodal distribution under annealing, as analyzed by positron annihilation lifetime spectroscopy (PALS). The emergence of the bimodal distribution is probably ascribed to the synergetic effect of quenching and thermal cyclization reaction. In addition, the fractional free volume (FFV) of the membranes presents a concave trend with increasing annealing temperature. Vapor sorption tests reveal that the mass transport properties are closely associated with the free volume evolution, which provides an optimal condition for dehydration of biofuels. A promising separation performance with extremely high water permeability has been attained for dehydration of an 85 wt % ethanol aqueous solution at 45 °C. The study on the free volume evolution of the TFM membranes may provide useful insights about the microstructure and mass transport behavior of the microporous polymeric materials.

Restricted Access: On the Nature of Adsorption/Desorption Hysteresis in Amorphous, Microporous Polymeric Materials

The phenomenon of low-pressure adsorption/desorption hysteresis, which is commonly observed in microporous polymers, is investigated by detailed gas adsorption studies. Diffusional limitations by pore blocking effects, which arise as a consequence of the micropore morphology and connectivity, are discussed as the origin of the hysteresis rather than swelling effects, which have been suggested previously. Micropores with narrow openings, which cannot be filled easily, are expected to be present next to open pores. Those pores are termed restricted-access pores and are only filled in the course of the adsorption process as a consequence of the increasing solvation pressure exhibited from already filled micropores. As a consequence of the results presented here, it is suggested to use the desorption branch in addition to the adsorption branch for the extraction of the porosity characteristics, such as specific surface area, pore volume, and pore size distribution. The magnitude of the low-pressure hysteresis might hence give an idea of the micropore connectivity, which is important information for potential applications.

Design and manufacture of microporous polymeric materials with hierarchal complex structure for biomedical application

Porous biodegradable polymeric scaffolds are essential for tissue engineering application since they should provide the adequate three-dimensional structure for cellular attachment and tissue development. In particular, pore size and shape and overall porosity are key structural features in controlling neotissue formation. Since scaffolds structural properties play a relevant role in all processes involved in tissue genesis including cell adhesion, migration, proliferation, growth, differentiation and biosynthesis, an accurate control over the pore size and its distribution, pore shape, pore interconnectivity, and overall porosity of scaffolds is mandatory for the success of any tissue engineering approach. Several methods have been proposed to tailor make porous scaffolds to obtain the desired pore structure. Here, three techniques to emboss a controlled pattern of porosity in biodegradable polymers, particulate leaching, phase separation and gas foaming along with their combinations, are critically reviewed highlighting process–structure–property relationship.

Permeable, Microporous Polymeric Membrane Materials Constructed from Discrete Molecular Squares

Microporous polyester membranes (see Figure) have been formed via interfacial polymerization. The reactants were porphyrin‐based square assemblies functionalized with phenol groups and bis(acid chloride) linkers. The membranes are free‐standing and display size‐selective porosity, allowing transport of molecules smaller than the intra‐square cavity and displaying blocking behavior with respect to larger molecules.

Theoretical Modeling of Mechanical Resistance and Stability and Related Characteristics of Polymeric Systems with Branching/Cross-Linking

A theoretical (thermodynamic) method for the estimation of mechanical characteristics of polymeric systems is proposed. This method uses the statistical polymer method for modeling of branched/cross-linked structures. The weak interaction between macromolecules is modeled in the approach of their mutual interpenetration. The proposed method is used for the estimation of mechanical resistance and stability of microporous polymeric materials. An engineer method for the evaluation of mechanical stability and resistance of polymeric materials is derived.

Modeling of Mechanical Properties of Polymeric Systems with Branching/Crosslinking, Particularly Their Mechanical Resistence and Stability

A theoretical method for the estimation of mechanical characteristics of polymeric structures is proposed. This method uses the statistical polymer method for modeling branched/crosslinked structures. The proposed method is utilized for the estimation of mechanical resistance and stability of microporous polymeric materials. An engineering method for the evaluation of mechanical stability and resistance of polymeric materials is derived.

Modeling of Mechanical Properties of Polymeric Systems with Branching/Crosslinking, Particularly Their Mechanical Resistence and Stability

A theoretical method for the estimation of mechanical characteristics of polymeric structures is proposed. This method uses the statistical polymer method for modeling branched/crosslinked structures. The proposed method is utilized for the estimation of mechanical resistance and stability of microporous polymeric materials. An engineering method for the evaluation of mechanical stability and resistance of polymeric materials is derived.

Formation of microporous polymeric materials by microemulsion radiation polymerization of butyl acrylate

A microemulsion system composed of butyl acrylate (BA) and water with a mixture of sodium 12-acryloxy-9-octadecenate (SAO) and octylphenoxypoly(ethoxyethanol) as an emulsifier was initiated by γ-ray radiation at room temperature to polymerize and produce microporous polymeric materials. The morphology and swelling characteristics of the resulting polymeric materials were studied. It was found that they strongly depended on the composition (water content, crosslinker content, emulsifier content) of the precursor microemulsions. In addition, the swelling properties of the polymer so prepared were found to be sensitive to the pH of the swelling medium. The change in swelling behaviors of the polymeric materials is discussed in terms of the polyelectrolyte effect exhibited by the polymerized anionic emulsifier SAO. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1989–1993, 2000

Microporous polymeric materials by microemulsion polymerization: effect of the ratio of long and short alkyl chain length cationic surfactants

Bicontinuous microemulsions consisting of methyl methacrylate, 2-hydroxyethyl methacrylate, ethylene glycol dimethacrylate, and water mixtures of long and short alkyl chain length cationic n-alkyltrimethyl-ammonium bromides as surface-active agent, were used as precursors for the formation of porous polymeric materials. It was found that the mixing ratio of long and short chain length surfactants has a pronounced influence on the morphology and microstructure of the polymeric materials so obtained. At a particular ratio of long to short alkyl chain length cationic surfactants, the pores were found to be irregular and sponge-like in structure resembling that of a bicontinuous structure. All electron microscopy investigation, swelling and permeability studies indicate an increase in pore sizes of the polymeric materials on increasing the weight ratio of long chain length relative to that of short chain length surfactant. The modification in the microstructure of the polymeric materials is discussed in terms of the interfacial film rigidity.

Formation of microporous polymeric materials by microemulsion polymerization of methyl methacrylate and 2-hydroxyethyl methacrylate

The investigated microemulsion system consisted of methyl methacrylate, 2-hydroxyethyl methacrylate and water using sodium dodecyl sulphate as surfactant. Ethylene glycol dimethacrylate acting as a cross-linker was also incorporated to enhance the mechanical strengths of the microporous polymeric materials. The polymerization was carried out at room temperature using a reactive redox initiator comprising ammonium persulphate and N,N,N′,N′-tetramethylethylene diamine. The conductivities of the microemulsion samples were monitored during the course of polymerization. The conductivities for a bicontinuous microemulsion before and after polymerization were found to be very similar. In addition, the transformation of microstructures was also examined using a transmission as well as a field emission scanning electron microscope. It is evidenced from the micrographs that microporous polymeric materials prepared from bicontinuous microemulsion polymerization are attributed to numerous coagulations of spherical particles. A possible mechanism for the microstructural transformation is discussed based on the information of conductivity measurements and electron micrographs. © 1996 John Wiley & Sons, Inc.

Microporous polymeric materials by polymerization of microemulsions containing different alkyl chain lengths of cationic surfactants

Abstract Microemulsion systems formulated with methyl methacrylate, 2-hydroxyethyl methacrylate, cross-linking agent, ethylene glycol dimethacrylate (EGDMA) and water using cationic surfactants of n-alkyl trimethyl ammonium bromide with alkyl chain lengths varying from C12 to C16 have been investigated. Photoinitiated polymerization was carried out only for bicontinuous microemulsion samples to form microporous polymeric materials. The opacity of the resulting polymeric materials decreased with the use of shorter alkyl chain lengths of the cationic surfactants. In addition, the morphology of the microporous polymeric solids as observed by Field Emission Scanning Electron Microscope shows a drastic change from worm-like, oval-shaped to globular structures on decreasing the alkyl chain length of the surfactant at a particular concentration. These polymeric materials possessed open-cell structures. Their pore sizes were smaller and their pore volume distributions were narrower for polymer samples using shorter alkyl chain-length surfactants. This study shows the feasibility of controlling the microstructures and pore dimensions of the polymeric materials prepared by polymerization of bicontinuous microemulsions containing different alkyl chain lengths of cationic surfactants.

Microporous Polymeric Materials by Microemulsion Polymerization: Effect of Surfactant Concentration

The microemulsion system comprising water, methyl methacrylate, 2-hydroxyethyl methacrylate, and n-dodecyltrimethylammonium bromide was polymerized and cross-linked with ethylene glycol dimethacrylate. Fast polymerization of the microemulsions to form solid polymers could be easily obtained using dibenzyl ketone as a photoinitiator. Morphology of the resulting polymeric materials formed from bicontinuous microemulsions indicates the existence of open-cell type microporous structures as determined by thermogravimetric analysis. Their pore sizes, as revealed by field emission electron microscope, decreased on increasing the surfactant concentration. This study provides the first simple method for varying the pore size of polymeric materials by microemulsion polymerization of a suitable system using different surfactant concentrations.

Microporous Polymeric Materials from Polymerization of Zwitterionic Microemulsions

A new microemulsion system consisting of a polymerizable zwitterionic surfactant of (((acryloyloxy)undecyl)dimethylammonio)acetate (AUDMAA), methyl methacrylate (MMA), water with or without a cross-linking agent of ethylene glycol dimethacrylate (EGDMA) was investigated. Transparent solid polymeric materials can be produced by photoinitiated polymerization of some of these microemulsion compositions. Microemulsions with higher concentrations of EGDMA (>4%) or MMA (>50%) produced only turbid polymeric materials. However, it required a minimum of about 25% AUDMAA for producing a transparent polymeric material. Most of the bicontinuous microemulsions investigated could be gelled within 10 min and transparent solid polymers were finally obtained. Electron micrographs of these transparent polymers reveal the existence of not only the open-cell type microstructures but also the bicontinuous nature. The widths of the bicontinuous structures were about 50-70 nm, their lengths were long and winding and they appear to be randomly distributed. The microporous structures of these transparent polymeric materials seem to be related to the microstructures of the precursor bicontinuous-microemulsions. Perhaps, this is the first report to show the bicontinuous structures of microporous polymeric materials prepared by microemulsion polymerization.

Morphology of microporous polymeric materials by polymerization of methyl methacrylate and 2-hydroxyethyl methacrylate in microemulsions

A microemulsion system consisting of methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA) and a crosslinking agent, ethylene glycol dimethacrylate, in water using sodium dodecyl sulfate as a surface-active agent was investigated. A study on the phase behaviour of the system was conducted to determine the type of microstructures that may be present. Polymerization was carried out at room temperature using dibenzyl ketone as a photoinitiator. The morphology (microstructure) of the resulting polymeric materials was found to depend strongly on the composition (water content, surfactant content, and MMA to HEMA ratio) of the precursor microemulsions.