Nonporous Polymer Research Articles

Synthesis, Characterization, and Gas Adsorption Performance of Amine-Functionalized Styrene-Based Porous Polymers

In recent years, porous materials have been extensively studied by the scientific community owing to their excellent properties and potential use in many different areas, such as gas separation and adsorption. Hyper-crosslinked porous polymers (HCLPs) have gained attention because of their high surface area and porosity, low density, high chemical and thermal stability, and excellent adsorption capabilities in comparison to other porous materials. Herein, we report the synthesis, characterization, and gas (particularly CO2) adsorption performance of a series of novel styrene-based HCLPs. The materials were prepared in two steps. The first step involved radical copolymerization of divinylbenzene (DVB) and 4-vinylbenzyl chloride (VBC), a non-porous gel-type polymer, which was then modified by hyper-crosslinking, generating micropores with a high surface area of more than 700 m2 g-1. In the following step, the polymer was impregnated with various polyamines that reacted with residual alkyl chloride groups on the pore walls. This impregnation substantially improved the CO2/N2 and CO2/CH4 adsorption selectivity.

The Increasing Number of Electron Reservoirs in Nonporous, High-Conducting Coordination Polymers Cux BHT (x=3, 4, and 5, BHT=Benzenehexathiol) for Improved Faradaic Capacitance.

Although asymmetric supercapacitors (ASCs) can achieve high energy density, the lifespan and power density are severely suppressed due to the low conductivity of using pseudocapacitive or battery-type electrode materials. Recently, nonporous conductive coordination polymers (c-CPs) have sparked interests in supercapacitors. However, their performance is expected to be limited by the nonporous features, low specific surface area and absence of ion-diffusion channels. Here, it is demonstrated that the capacity of nonporous CPs will be significantly enhanced by maximizing the number of faradaic redox sites in their structures through a comparative investigation on three highly conductive nonporous c-CPs, Cux BHT(x=3, 4, 5.5). They show excellent capacitance of 312.1Fg-1 (374.5Cg-1 ) (Cu3 BHT), 186.7Fg-1 (224.0Cg-1 ) (Cu4 BHT) and 89.2Fg-1 (107.0Cg-1 ) (Cu5.5 BHT) at 0.5Ag-1 in a sequence related to the number of electron storage units in structures and outstanding rate performance and cycle stability. Furthermore, the constructed Cu3 BHT//MnO2 ASC device exhibits capacity retention of 92% (after 1500 cycles at 3Ag-1 ) and delivers a high energy density of 39.1Whkg-1 at power density of 549.6Wkg-1 within a large working potential window of 0-2.2V.

Water vapour induced reversible switching between a 1-D coordination polymer and a 0-D aqua complex.

[Zn(3-tba)2], 1, a 1-D coordination polymer synthesised as 1 DMA, 1α, transformed to a nonporous form, 1β, upon activation. 1β underwent further transformation to the dimeric complex [Zn(3-tba)2(H2O)2], 2, above 40% RH. The reverse transformations, 2 to 1β and 1β to 1α, were accomplished by heating and exposure to DMA, respectively, and were single-crystal-to-single-crystal phase changes. Single crystal X-ray diffraction revealed that the second transformation resulted from Zn-carboxylate bond breakage and concomitant coordination of water molecules. Other solvent molecules did not induce a phase change.

Crystallographic Visualization of a Guest-Induced Solar-Driven Cycloaddition Reaction Based on a Recyclable Nonporous Coordination Polymer.

Stimuli-responsive solids with adjustable photophysical properties are particularly attractive because they can be used as smart materials in anticounterfeiting, information storage, holographic imaging, and other fields. Herein, we report a unique nonporous coordination polymer, {[Ag(3,3'-dpe)](2,2'-Hbpdc)}n (1; 3,3'-dpe = 1,2-dipyridin-3-ylethene and 2,2'-H2bpdc = 2,2'-biphenyldicarboxylic acid), that can convert to an extremely photoreactive compound, 1·H2O·MeCN (MeCN = acetonitrile), through guest capture. Upon irradiation of sunlight, 1·H2O·MeCN can transform to {[Ag(3,3'-tpcb)0.5](2,2'-Hbpdc)(H2O)(MeCN)}n (2·H2O·MeCN; 3,3'-tpcb = 1,2,3,4-tetrapyridin-3-ylcyclobutane). 2·H2O·MeCN can lose its solvent molecules to form 2 and further return to 1 at high temperature. Accompanied by direct visualization based on multistep single-crystal-to-single-crystal conversions, the recyclable crystalline solid exhibits remarkable fluorescence changes, which makes it a supramolecular switch for application in multiple anticounterfeiting.

Tunable Proton Conductivity and Color in a Nonporous Coordination Polymer via Lattice Accommodation to Small Molecules.

Nonporous coordination polymers (npCPs) able to accommodate molecules through internal lattice reorganization are uncommon materials with applications in sensing and selective gas adsorption. Proton conduction, extensively studied in the analogue metal‐organic frameworks under high‐humidity conditions, is however largely unexplored in spite of the opportunities provided by the particular sensitivity of npCPs to lattice perturbations. Here, AC admittance spectroscopy is used to unveil the mechanism behind charge transport in the nonporous 1·2CH3CN. The conductance in the crystals is found to be of protonic origin. A vehicle mechanism is triggered by the dynamics of the weakly coupled acetonitrile molecules in the lattice that can be maintained by a combination of thermal cycles, even at low humidity levels. An analogue 1·pyrrole npCP is formed by in situ exchange of these weakly bound acetonitrile molecules by pyrrole. The color and conduction properties are determined by the molecules weakly bonded in the lattice. This is the first example of acetonitrile‐mediated proton transport in an npCP showing distinct optical response to different molecules. These findings open the door to the design of switchable protonic conductors and capacitive sensors working at low humidity levels and with selectivity to different molecules.

Effects of environmental temperature and humidity on evaporative heat loss through firefighter suit materials made with semi-permeable and microporous moisture barriers

The goal of this research was to understand how firefighter protective suits perform in different operational environments. This study used a sweating guarded hotplate to examine the effect of environmental temperature (20–45°C) and relative humidity (25–85% RH) on evaporative heat loss through firefighter turnout materials. Four firefighter turnout composites containing three different bi-component (semi-permeable) and one microporous moisture barriers were selected. The results showed that the evaporative resistance of microporous moisture barrier systems was independent of environmental testing conditions. However, absorbed moisture strongly affected evaporative heat loss through semi-permeable moisture barriers coated with a layer of nonporous hydrophilic polymer. Moisture absorption in mild environment (20–25°C) tests, or when testing at high humidity (>85% RH), significantly increased water vapor transmission in semi-permeable turnout systems. It was also found that environmental conditions used in the total heat loss (THL) test (25°C and 65% RH) produced moisture condensation in bi-component barrier systems, making them appear more breathable than could be expected when worn in hotter environments. Regression models successfully qualified the relationships between moisture uptake levels in semi-permeable barrier systems and evaporative resistance and THL. These findings reveal the limitations in relying on THL, the heat strain index currently called for by the NFPA 1971 Standard for Structural Firefighter personal protective equipment, and supports the need to measure turnout evaporative resistance at 35°C (Ret), in addition to THL at 25°C.

Chromatographic analysis of site-specific antibody-drug conjugates produced by AJICAP first-generation technology using a recombinant FcγIIIa receptor-ligand affinity column

Commercially approved conventional antibody-drug conjugates (ADCs) are produced as heterogeneous mixtures containing a stochastic distribution of payloads decorating the antibody molecules resulting in decreased efficacy and thus lowering their therapeutic index. Control of the DAR and conjugation site in the development of next-generation ADCs is believed to assist in increasing the therapeutic index of these targeted biologics leading to overall enhanced clinical efficacy and reduced toxicity. A chemical site-specific conjugation technology termed AJICAP® allows ADC developers to control both the location and quantity of the payload conjugation to an antibody. Furthermore, this simplified ADC composition enables a streamlined chemical analysis. Here we report the chromatographic separation of site-specific ADCs produced by AJICAP® technology using an analytical affinity chromatography HPLC column containing a recombinant FcγIIIa receptor-ligand immobilized on a non-porous polymer resin (NPR). These HPLC analyses provided visually clear chromatogram results reflecting the heterogeneity of each ADC. The affinity strength was also measured by biolayer interferometry (BLI) and predicted by molecular structure analysis. The results indicate that AJICAP® technology is a promising solution to link hydrophobic payloads to antibodies without compromising antibody receptor function. This study also shows that FcγIIIa-NPR column can be used to characterize site-specific conjugated ADCs compared to ADCs synthesized using conventional methods.

Redox Donor-Acceptor Conjugated Microporous Polymers as Ultralong-Lived Organic Anodes for Rechargeable Air Batteries.

Herein, we explore a new redox donor-acceptor conjugated microporous polymer (AQ-CMP) by utilizing anthraquinone and benzene as linkers via C-C linkages and demonstrate the first use of CMP as ultralong-lived anodes for rechargeable air batteries. AQ-CMP features an interconnected octupole network, which affords not only favorable electronic structure for enhanced electron transport and n-doping activity compared to linear counterpart, but also high density of active sites for maximizing the formula-weight-based redox capability. This coupled with highly cross-linked and porous structure endows AQ-CMP with a specific capacity of 202 mAh g-1 (96 % of theoretical capacity) at 2 Ag-1 and ≈100 % capacity retention over 60000 charge/discharge cycles. The assembled CMP-air full cell shows a stable and high capacity with full capacity recovery after only refreshing cathodes, while the decoupled electrolyte and cathode design boosts the discharge voltage and voltage efficiency to ≈1 V and 87.5 %.

Nonporous Gel Electrolytes Enable Long Cycling at High Current Density for Lithium-Metal Anodes.

Lithium-metal anodes with high theoretical capacity and ultralow redox potential are regarded as a "holy grail" of the next-generation energy-storage industry. Nevertheless, Li inevitably reacts with conventional liquid electrolytes, resulting in uneven electrodeposition, unstable solid electrolyte interphase, and Li dendrite formation that all together lead to a decrease in active lithium, poor battery performance, and catastrophic safety hazards. Here, we report a unique nonporous gel polymer electrolyte (NP-GPE) with a uniform and dense structure, exhibiting an excellent combination of mechanical strength, thermal stability, and high ionic conductivity. The nonporous structure contributed to a uniform distribution of lithium ions for dendrite-free lithium deposition, and Li/NP-GPE/Li symmetric cells can maintain an extremely low and stable polarization after cycling at a high current density of 10 mA cm-2. This work provides an insight that the NP-GPE can be considered as a candidate for practical applications for lithium-metal anodes.

Crystal Structure-Free Method for Dielectric and Polarizability Characterization of Crystalline Materials at Terahertz Frequencies.

Terahertz (THz) time-domain spectroscopy provides a direct and nondestructive method for measuring the dielectric properties of materials directly from the phase delay of coherent electromagnetic radiation propagating through the sample. In cases when crystals are embedded within an inert polymeric pellet, the Landau, Lifshitz, and Looyenga (LLL) effective medium model can be used to extract the intrinsic dielectric constant of the crystalline sample. Subsequently, polarizability can be obtained from the Clausius-Mossotti (CM) relationship. Knowledge of the crystal structure density is required for an analytical solution to the LLL and CM relationships. A novel crystal structure-free graphical method is presented as a way to estimate both dielectric constants and polarizability values for the situation when the crystal structure density is unknown, and the crystals are embedded within a pellet composed of a non-porous polymer. The utility of this crystal structure-free method is demonstrated by analyzing THz time-domain spectra collected for a set of amino acids (L-alanine, L-threonine, and L-glutamine) embedded within pellets composed of polytetrafluoroethylene. Crystal structures are known for each amino acid, thereby enabling a direct comparison of results using the analytical solution and the proposed crystal structure-free graphical method. For each amino acid, the intrinsic dielectric constant is extracted through the LLL effective medium model without using information of their crystal structure densities. THz polarizabilities are then calculated with the CM relationship by using the determined intrinsic dielectric constant for each amino acid coupled with its crystal density as determined graphically. Comparison between the analytical and graphical solutions reveal relative differences between dielectric constants of 3.7, 5.1, and 13.6% for threonine, alanine, and glutamine, respectively, and relative differences between polarizability of 0.6, 0.9, and 5.4%, respectively. These values were determined over the 10-20 cm-1 THz frequency range. The proposed method requires no prior knowledge of crystal structure information.

Catalyst: Challenges in development of adsorbents for recovery of uranium from seawater

Sheng Dai is currently a section head of separations and polymer chemistry and a UT-Battelle Corporate Fellow at the Chemical Sciences Division of the Oak Ridge National Laboratory and a professor of chemistry at the University of Tennessee, Knoxville. He served as a national technical director for a US Department of Energy project aimed at recovering uranium from seawater (2010–2016). His current research interests include ionic liquids, porous materials, and their applications for separation sciences and energy storage, as well as catalysis by nanomaterials.

Long Afterglow of a Nonporous Coordination Polymer with Tunable Room-Temperature Phosphorescence by the Doping of Dye Molecules.

Metal-organic frameworks (MOFs) or coordination polymers (CPs)-based phosphorescence materials may provide a powerful route for photoelectric and optical recording devices. Herein, two phosphorescence ligands, iso-phthalic acid (IPA) and 2-methylimidazole (MIM), were selected to construct an nonporous CP {Zn(IPA)(MIM)2} (1) with a long-lived phosphorescence lifetime up to 552 ms. By the doping of Eosin Y (EY) dye molecules under an in situ process, the phosphorescence emission color of 1 can be expressly tuned from green to red. The light-harvesting range can also be vastly broadened from the UV to the visible region (550 nm). Photoelectron measurements reveal that the synergistic effect of bias voltage and illumination can greatly restrain electron-hole recombination for the generation of additional free charges.

Large breathing effect induced by water sorption in a remarkably stable nonporous cyanide-bridged coordination polymer.

While metal–organic frameworks (MOFs) are at the forefront of cutting-edge porous materials, extraordinary sorption properties can also be observed in Prussian Blue Analogs (PBAs) and related materials comprising extremely short bridging ligands. Herein, we present a bimetallic nonporous cyanide-bridged coordination polymer (CP) {[Mn(imH)]2[Mo(CN)8]}n (1Mn; imH = imidazole) that can efficiently and reversibly capture and release water molecules over tens of cycles without any fatigue despite being based on one of the shortest bridging ligands known – the cyanide. The sorption performance of {[Mn(imH)]2[Mo(CN)8]}n matches or even outperforms MOFs that are typically selected for water harvesting applications with perfect sorption reversibility and very low desorption temperatures. Water sorption in 1Mn is possible due to the breathing effect (accompanied by a dramatic cyanide-framework transformation) occurring in three well-defined steps between four different crystal phases studied structurally by X-ray diffraction structural analysis. Moreover, the capture of H2O by 1Mn switches the EPR signal intensity of the MnII centres, which has been demonstrated by in situ EPR measurements and enables monitoring of the hydration level of 1Mn by EPR. The sorption of water in 1Mn controls also its photomagnetic behavior at the cryogenic regime, thanks to the presence of the [MoIV(CN)8]4− photomagnetic chromophore in the structure. These observations demonstrate the extraordinary sorption potential of cyanide-bridged CPs and the possibility to merge it with the unique physical properties of this class of compounds arising from their bimetallic character (e.g. photomagnetism and long-range magnetic ordering).

New Promises and Opportunities in 3D Printable Inks Based on Coordination Compounds for the Creation of Objects with Multiple Applications.

This review focuses on the usefulness of coordination bonds to create 3D printable inks and shows how the union of chemistry and 3D technology contributes to new scientific advances, by allowing amorphous or polycrystalline solids to be transformed into objects with the desired shape for successful applications. The review clearly shows how there has been considerable increase in the manufacture of objects based on the combination of organic matrices and coordination compounds. These coordination compounds are usually homogeneously dispersed within the matrix, anchored onto a proper support or coating the printed object, without destroying their unique properties. Advances are so rapid that today it is already possible to 3D print objects made exclusively from coordination compounds without additives. The new printable inks are made mainly with nanoscale nonporous coordination polymers, metal-organic gels, or metal-organic frameworks. The highly dynamic coordination bond allows the creation of objects, which respond to stimuli, that can act as sensors and be used for drug delivery. In addition, the combination of metal-organic frameworks with 3D printing allows the adsorption or selective capacity of the object to be increased, relative to that of the original compound, which is useful in energy storage, gas separation, or water pollutant elimination. Furthermore, the presence of the metal ion can give them new properties, such as luminescence, that are useful for application in sensors or anticounterfeiting. Technological advances, the combination of various printing techniques, and the properties of coordination bonds lead to the creation of surprising, new, printable inks and objects with highly complex shapes that will close the gap between academia and industry for research into coordination compounds.

Porous and Nonporous Coordination Polymers Induced by Pseudohalide Ions for Luminescence and Gas Sorption.

The three-dimensional (3D) coordination polymers [Cd(tpmd)(NCX)2]n [X = O (1), S (2), and BH3 (3); tpmd = N,N,N',N'-tetrakis(pyridin-4-yl)methanediamine] have been determined to display their network structures through coordinated anionic ligands. Polymers 1 and 2 show nonporous structures, whereas polymer 3 shows a porous coordination framework. On the basis of the Cd(II) network structures, the 3D coordination polymer [Zn(tpmd)(NCBH3)2]n·nMeOH (4) was self-assembled. In the cases of polymers 1 and 2, pseudohalide ions acted to form nonporous network structures; however, in polymers 3 and 4, NCBH3- helps to construct porous network structures. Polymers 1-4 show strong ultraviolet luminescence emissions, depending on the pseudohalide ions present, compared to the tpmd ligands. Interestingly, coordination polymers 3 and 4 that possess NCBH3- ions exhibit high porosities and gas sorption properties. The polymers appeared to absorb N2, H2, CO2, and CH4. In the case of polymer 4, the structure is almost identical with that of polymer 3, except for the Cd(II) ion. However, polymer 4 has a larger void volume and higher gas absorption ability for N2 gas than polymer 3. For the sorption of gases, polymers 3 and 4 showed similar behaviors.

Stationary Phase Based on Hypercrosslinked Polystyrene for Capillary Gas Chromatography

A capillary column for gas chromatography was prepared using microspherical particles of hypercrosslinked polystyrene. The hypercrosslinked stationary phase approximates the stationary phases based on the poly(trimethylsilylpropyne) membrane polymer according to the sorption enthalpy of light hydrocarbons, but proved markedly inferior to the latter phases according to the kinetic efficiency. Direct synthesis in a column with a hypercrosslinked stationary phase based on hypercrosslinked polystyrene led to the formation of a nonporous polymer, which had no separating ability with respect to light hydrocarbons.

Hierarchically Porous Carbons Derived from Nonporous Coordination Polymers.

Hierarchically porous carbons (HPCs) with multimodal pore systems exhibit great technological potentials, especially in the fields of heterogeneous catalysis, energy storage, and conversion. Here, we establish a simple and general approach to HPCs by carbonization of nonporous coordination polymers that are produced by mixing metal salts with polytopic ligands in alkaline aqueous solutions at room temperature. The proposed approach is applicable to a wide scope of ligand molecules (18 examples), thus affording the synthesized HPCs with high diversity in porosity, morphology, and composition. In particular, the prepared HPCs exhibit high specific surface areas (up to 2647 m2 g-1) and large pore volumes (up to 2.39 cm3 g-1). The HPCs-supported atomically dispersed Fe-Nx catalysts show much-improved fuel cell cathode performance over the micropore-dominated carbon black-supported catalysts, demonstrating the structural superiority of the HPCs for enhancing the mass transport properties.

Fabrication of a porous polymer membrane enzyme reactor and its enzymatic kinetics study in an artificial kidney model

A porous polymer membrane-based d-amino acid oxidase (DAAO) reactor was developed that mimicked enzymatic activity in a renal ischemia model. Using glycidyl methacrylate as a biocompatible reactive monomer, poly(styrene-glycidyl methacrylate) was synthesized via a reversible addition fragment chain transfer polymerization technique. The prepared porous polymer membrane was used as a support to effectively immobilize DAAO. Compared to DAAO modified on nonporous polymer membrane and free DAAO in solution, the constructed porous polymer membrane-based DAAO enzyme reactor displayed 3-fold and 19-fold increase in enzymolysis efficiency, respectively. In addition, a chiral ligand exchange capillary electrophoresis system for DAAO was used to study DAAO enzymatic kinetics with d,l-methionine as the substrate. The proposed porous polymer membrane-based enzyme reactor showed excellent performance both on reproducibility and stability. Moreover, the enzyme reactor was successfully applied to mimic DAAO activity in a renal ischemia model. These results demonstrated that the enzyme could be efficiently immobilized onto a porous polymer membrane as an enzyme reactor and has great potential in mimicking the enzymatic activity in kidney.

Porous Metal-Organic Frameworks Containing Reversible Disulfide Linkages as Cathode Materials for Lithium-Ion Batteries.

Three porous disulfide-ligand-containing metal-organic frameworks (DS-MOFs) and two nonporous coordination polymers with disulfide ligands (DS-CPs) with various structural dimensionalities were used as cathode active materials in lithium batteries. Charge/discharge performance examinations revealed that only porous DS-MOF-based batteries exhibited significant capacities close to the theoretical values, which was ascribed to the insertion of electrolyte ions into the DS-MOFs. The insolubility of porous 3 D DS-MOFs in the electrolyte resulted in cycling performances superior to that of their 1 D and 2 D porous counterparts. Battery reactions were probed by instrumental analyses. The dual redox reactions of metal ions and disulfide ligands in the MOFs resulted in higher capacities, and the presence of reversible electrochemically dynamic S-S bonds stabilized the cycling performance. Thus, the strategy of S-S moiety trapping in MOFs and the obtained correlation between the structural features and battery performance could contribute to the design of high-performance MOF-based batteries and the practical realization of Li-S batteries.

Repurposing biodegradable tissue engineering scaffolds for localized chemotherapeutic delivery.

While highly porous biodegradable sponges have typically been used as tissue engineering scaffolds, they could be applicable in settings requiring drug delivery. Since most drug delivery devices are intentionally solid, nonporous polymers, a detailed structure-function relationship of delivery from a porous degradable sponges would allow researchers to develop such devices for either delivery alone, or in conjunction with tissue engineering. Two fabrication techniques (salt-leaching and solvent-quenching) were used to prepare several different variations of poly(DL-lactide-glycolide) and poly(caprolactone)-co-poly(lactide) porous sponges. Upon fabrication, an in-depth structure-function analysis was carried out where the functions of loading capacity and release profile of cisplatin, as a model drug, were evaluated in terms of the swelling, porosity, and degradation properties of the sponges. Swelling, pore volume fraction, and the number of pores per volume were all found to be positively correlated with both the loading capacity and amount of cisplatin released after 2 hr. Knowledge of these relationships can be used to assist in the design of other porous delivery systems.